NS Military Realism Consultation Thread Vol. 11.0

[Austrasien]

Sectional density rises with calibre because the density of materials is basically a constant. Barrel twist is more or less whatever you want it to be, the only absolute limit is on L/D ratio, but this is essentially size-independent. 6mm bullets have the same L/D limitations as 7.62mm and 5.56mm bullets. Aerodynamics scale well and a bullet form which provides low drag and good stability at one calibre can be scaled up or down to other calibres with little difficulty.

There is nothing special about the 6mm calibre range which is inherent to the calibre. Comparable low drag bullets for calibres including 7.62 and 5.56mm are not just practical, they are readily available to hand loaders. As are a wide range of other calibres. The best that can be said about 6mm bullets is they may offer good drag characteristics at a reasonable recoil impulse. But the practical effects of recoil beyond less = better are not well characterized, so it is largely subjective whether or not a given cartridge kicks "too much".

[Spirit of Hope]

The 5.56mm is about the same weight as a rain drop, and is notorious for bouncing off of windows and being stopped by very small amounts of sand.

Reduced Penetration. Even with reduced penetration at short ranges, interior walls made of thin wood paneling, sheetrock, or plaster are no protection against 5.56mm ball ammunition rounds. Common office furniture, such as desks and chairs, cannot stop these rounds, but a layer of books 18 to 24 inches (457 to 610 mm) thick can.

Wood and Cinder Blocks. Wooden frame buildings and single cinder block walls offer little protection from 5.56mm rounds. When clearing such structures, soldiers must ensure friendly casualties do not result from rounds passing through walls, floors, or ceilings.

The following common barriers in urban areas stop a 5.56mm round fired at less than 50 meters:
One thickness of well-packed sandbags.
A 2 inch (51 mm) non-reinforced concrete wall.
A 55 gallon drum filled with water or sand.
A small ammunition can filled with sand.
A cinder block filled with sand (block will probably shatter).
A plate glass windowpane at a 45° angle (glass fragments may be thrown behind the glass).
A brick veneer.
A car body (round will penetrate but normally not exit).

I was unaware a full, well packed, sandbag was "a little bit of sand," and that plate glass at 45° angle was a "window." Of course 7.62 isn't that much better:

Barriers that offer protection against 5.56mm rounds are also effective against 7.62mm rounds with some exceptions. The 7.62mm round can penetrate a windowpane at a 45° obliquity, a hollow cinder block, or both sides of a car body.

At 50 meters, the 7.62mm ball round cannot reliably penetrate a single layer of well-packed sandbags

From the same sight.

[Triplebaconation]

The 5.56mm is about the same weight as a rain drop

This doesn't even pass the most cursory bullshit test. A bullet is 8-11 times denser than water, so a raindrop weighing the same as a 5.56mm bullet will have to be 8-11 times larger. That's a hell of raindrop!

In fact, the maximum diameter of a falling raindrop is about 5mm (although larger ones can exist in clouds) so a large raindrop will weigh about 65 milligrams. Or 1 grain.

6mm PPC is a specialized benchrest cartridge, and unsuitable for automatic weapons. I sincerely doubt there are any AKs chambered for it, though there are a few 6mm PPC AR match rifles.

[Triplebaconation]

Hence, one of the reasons I picked Greenland, another being I was hedging my bets in that most people actually know where Greenland is. Wasn't sure how many people who read this thread have as an extensive knowledge of Geography as I do

lol

[Manokan Republic]

The 5.56mm is about the same weight as a rain drop, and is notorious for bouncing off of windows and being stopped by very small amounts of sand.

Reduced Penetration. Even with reduced penetration at short ranges, interior walls made of thin wood paneling, sheetrock, or plaster are no protection against 5.56mm ball ammunition rounds. Common office furniture, such as desks and chairs, cannot stop these rounds, but a layer of books 18 to 24 inches (457 to 610 mm) thick can.

Wood and Cinder Blocks. Wooden frame buildings and single cinder block walls offer little protection from 5.56mm rounds. When clearing such structures, soldiers must ensure friendly casualties do not result from rounds passing through walls, floors, or ceilings.

The following common barriers in urban areas stop a 5.56mm round fired at less than 50 meters:
One thickness of well-packed sandbags.
A 2 inch (51 mm) non-reinforced concrete wall.
A 55 gallon drum filled with water or sand.
A small ammunition can filled with sand.
A cinder block filled with sand (block will probably shatter).
A plate glass windowpane at a 45° angle (glass fragments may be thrown behind the glass).
A brick veneer.
A car body (round will penetrate but normally not exit).

I was unaware a full, well packed, sandbag was "a little bit of sand," and that plate glass at 45° angle was a "window." Of course 7.62 isn't that much better:

Barriers that offer protection against 5.56mm rounds are also effective against 7.62mm rounds with some exceptions. The 7.62mm round can penetrate a windowpane at a 45° obliquity, a hollow cinder block, or both sides of a car body.

At 50 meters, the 7.62mm ball round cannot reliably penetrate a single layer of well-packed sandbags

From the same sight.

"A small ammunition can filled with sand."

Obviously a sandbag is a very substantial amount of sand. And poorly packed sandbags I have seen heavier rounds go through, mostly inbetween the cracks of the sandbags, so two is usually used, but one is sufficient if, well packed.

[Manokan Republic]

Sectional density rises with calibre because the density of materials is basically a constant. Barrel twist is more or less whatever you want it to be, the only absolute limit is on L/D ratio, but this is essentially size-independent. 6mm bullets have the same L/D limitations as 7.62mm and 5.56mm bullets. Aerodynamics scale well and a bullet form which provides low drag and good stability at one calibre can be scaled up or down to other calibres with little difficulty.

There is nothing special about the 6mm calibre range which is inherent to the calibre. Comparable low drag bullets for calibres including 7.62 and 5.56mm are not just practical, they are readily available to hand loaders. As are a wide range of other calibres. The best that can be said about 6mm bullets is they may offer good drag characteristics at a reasonable recoil impulse. But the practical effects of recoil beyond less = better are not well characterized, so it is largely subjective whether or not a given cartridge kicks "too much".

The issue is it fits within the realms of what people normally use, intermediate to full sized rifle levels of power. The 7.62mm bullets have to be too big and the 5.56mm are too small or ineffective. The 6mm to 6.5mm is around perfect, and a number of studies, tests, and of course anecdotal pieces of evidence bear this out. It's not that 6mm round are magic, it's that on average, they tend to be more accurate and more aerodynamic for their given size. 6mm rounds are generally more accurate, although this has more to do with bore chamber dimensions than anything else, which again are well suited for cartridges of that power level. People just don't use .300 win mags or 5.7mm rounds as primary combat rounds.

The issue with bullets that are too long being unstable doesn't really come up much, because few bullets are made that long, but there is an inherent instability issue. The .22 winchester, a .308 winchester magnum round necked down with a .223 sized bullet, had pretty bad stability, so much so that past 200 yards it was pretty difficult to use. A lot of these really ultra lightweight high velocity rounds tend to tumble quickly, and really long bullets have a similiar problem. Quick wikipedia thing: "For best performance, the barrel should have a twist rate sufficient to spin stabilize any bullet that it would reasonably be expected to fire, but not significantly more. Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer arm ("lever") to act on. The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 72 inches (180 cm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (120 cm) is very common. The M16A2 rifle, which is designed to fire the 5.56×45mm NATO SS109 ball and L110 tracer bullets, has a 1 in 7-inch (18 cm) or 32 calibers twist. Civilian AR-15 rifles are commonly found with 1 in 12 inches (30 cm) or 54.8 calibers for older rifles and 1 in 9 inches (23 cm) or 41.1 calibers for most newer rifles, although some are made with 1 in 7 inches (18 cm) or 32 calibers twist rates, the same as used for the M16 rifle. Rifles, which generally fire longer, smaller diameter bullets, will in general have higher twist rates than handguns, which fire shorter, larger diameter bullets."

While we rarely see bullets that are this unusually long, and thus have these problems, it's the reason why few .223 rounds designed to fill the same niche as the 6mm and 6.5mm bullets exist. Yes in theory you could do it, but it's much harder to pull it off. The twist rate would need to be unusually fast, and most really long bullets, like say a dart round, have their own stabilization methods instead, such as fins. "Extremely long projectiles such as flechettes may require high twist rates; these projectiles must be inherently stable, and are often fired from a smoothbore barrel." This is why a 6mm or 6.5mm is usually ideal for those selected criteria. 5.56mm is just generally too smol to really be effective at those weights and energy levels, unless the bullet is so long it becomes fairly unstable. The 5.6mm GP90 from the Swiss kind of illustrates this issue, being insanely accurate at close range, with .72 MOA for their standard assault rifle, achieved through a barrel twist of 1 in 12 (vs. 1 in 7 for most military barrels) and bullets optimized for it, but the rounds destabilizing quickly at 300-400 yards sort of mitigates their effectiveness. "The required accuracy for Gw Pat 90 ammunition out of factory test barrels is 63 mm (0.72 MOA) for 10 rounds (100% radius measurement method) out to 300 m." This comes at the cost of reduced stability, and thus reduced long range performance. Without getting in to rocket science territory, the 6mm and 6.5mm are ideal bullet sizes for 1000 meter ranges and moderate sized bullets, between an intermediate and rifle sized cartridge. It's not magic, it's just the ideal bullet size for most practical military purposes. At least according to my opinion and various military studies. Some of this is subjective in nature, and intuitive, but other elements have a more concrete base to them. Hypothetical capabilities and practical capabilities are two different things.

[Gallia-]

if you fill the ammo can with ammo it can be armor and ammo at the same time

[Manokan Republic]

if you fill the ammo can with ammo it can be armor and ammo at the same time

[Gallia-]

the cup should be balanced on a dozen ammo cans

[Spirit of Hope]

I was unaware a full, well packed, sandbag was "a little bit of sand," and that plate glass at 45° angle was a "window." Of course 7.62 isn't that much better:

From the same sight.

"A small ammunition can filled with sand."

Obviously a sandbag is a very substantial amount of sand. And poorly packed sandbags I have seen heavier rounds go through, mostly inbetween the cracks of the sandbags, so two is usually used, but one is sufficient if, well packed.

Yes a small ammunition can, probably about 3-5 inches thick, packed full with sand. It is basically a metal sand bag.

[Austrasien]

The issue is it fits within the realms of what people normally use, intermediate to full sized rifle levels of power. The 7.62mm bullets have to be too big and the 5.56mm are too small or ineffective. The 6mm to 6.5mm is around perfect, and a number of studies, tests, and of course anecdotal pieces of evidence bear this out. It's not that 6mm round are magic, it's that on average, they tend to be more accurate and more aerodynamic for their given size. 6mm rounds are generally more accurate, although this has more to do with bore chamber dimensions than anything else, which again are well suited for cartridges of that power level. People just don't use .300 win mags or 5.7mm rounds as primary combat rounds.

It might be worthwhile double-checking. 7.62-mm VLD bullets with ballistic coefficients equal or better to common 6.5-mm VLD loadings are available in the 175-185 grain range. No heavier than common 7.62-mm loadings. There is nothing about the 6-mm calibre which makes it more accurate inherently either. There are particular cartridges like the 6-mm PPC that are especially accurate, but this is not some magic property that is conferred on every cartridge with a bullet 6 or so mm in diameter.

The issue with bullets that are too long being unstable doesn't really come up much, because few bullets are made that long, but there is an inherent instability issue. The .22 winchester, a .308 winchester magnum round necked down with a .223 sized bullet, had pretty bad stability, so much so that past 200 yards it was pretty difficult to use. A lot of these really ultra lightweight high velocity rounds tend to tumble quickly, and really long bullets have a similiar problem. Quick wikipedia thing: "For best performance, the barrel should have a twist rate sufficient to spin stabilize any bullet that it would reasonably be expected to fire, but not significantly more. Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer arm ("lever") to act on. The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 72 inches (180 cm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (120 cm) is very common. The M16A2 rifle, which is designed to fire the 5.56×45mm NATO SS109 ball and L110 tracer bullets, has a 1 in 7-inch (18 cm) or 32 calibers twist. Civilian AR-15 rifles are commonly found with 1 in 12 inches (30 cm) or 54.8 calibers for older rifles and 1 in 9 inches (23 cm) or 41.1 calibers for most newer rifles, although some are made with 1 in 7 inches (18 cm) or 32 calibers twist rates, the same as used for the M16 rifle. Rifles, which generally fire longer, smaller diameter bullets, will in general have higher twist rates than handguns, which fire shorter, larger diameter bullets."

Correct twist rates for stabilization of a particular bullet is not difficult to determine for those with the appropriate knowledge. If a decision was made to move to a cartridge with very long, low drag bullets as a standard the correctly rifled barrels could be supplied. That a bullet won't be stabilized properly by an incorrect rifling twist is about as profound as the finding that it won't be sealed properly in an incorrectly sized bore.

If a particular bullet is unstable in flight this is a problem of the gun not the cartridge and certainly not the calibre. A lot more people play around with different cartridges more than different rifling twists, because most people don't bore their own barrels, but the fact they tried to fire a bullet down a barrel that was not appropriately rifled to stabilize it says nothing about the cartridge.

While we rarely see bullets that are this unusually long, and thus have these problems, it's the reason why few .223 rounds designed to fill the same niche as the 6mm and 6.5mm bullets exist. Yes in theory you could do it, but it's much harder to pull it off. The twist rate would need to be unusually fast, and most really long bullets, like say a dart round, have their own stabilization methods instead, such as fins. "Extremely long projectiles such as flechettes may require high twist rates; these projectiles must be inherently stable, and are often fired from a smoothbore barrel." This is why a 6mm or 6.5mm is usually ideal for those selected criteria. 5.56mm is just generally too smol to really be effective at those weights and energy levels, unless the bullet is so long it becomes fairly unstable. The 5.6mm GP90 from the Swiss kind of illustrates this issue, being insanely accurate at close range, with .72 MOA for their standard assault rifle, achieved through a barrel twist of 1 in 12 (vs. 1 in 7 for most military barrels) and bullets optimized for it, but the rounds destabilizing quickly at 300-400 yards sort of mitigates their effectiveness. "The required accuracy for Gw Pat 90 ammunition out of factory test barrels is 63 mm (0.72 MOA) for 10 rounds (100% radius measurement method) out to 300 m." This comes at the cost of reduced stability, and thus reduced long range performance. Without getting in to rocket science territory, the 6mm and 6.5mm are ideal bullet sizes for 1000 meter ranges and moderate sized bullets, between an intermediate and rifle sized cartridge. It's not magic, it's just the ideal bullet size for most practical military purposes. At least according to my opinion and various military studies. Some of this is subjective in nature, and intuitive, but other elements have a more concrete base to them. Hypothetical capabilities and practical capabilities are two different things.

As I already told you there is a length:diameter limit on spin-stabilized projectiles. But ALL spin-stabilized bullets exist within this limit by necessity, because aerodynamic forms are scaleable. This isn't even close to rocket science though it might be news to mall cops who "know about calibers".

A high L/D .223 or .308 bullet is perfectly accurate if it is fired out an appropriate weapon with the correct rifling twist, headspacing and whatnot. The only reason they would into issues is if they are fired out of rifles which were never meant to fire cartridges with such long bullets loaded into them, they hand loaded them badly, or both. And quite often this is going to be what is happening because people tend to be lazy and cheap - blame "unstable calibres" when you CBA to figure out the correct twist rate or botched the seating. Since chances these days are anyone firing 6.5-mm grendel or even danker 6-something mm "optimum" caliber cartridge bought an AR-upper expressly to fire 6.5-mm Grendel chances are that upper was already made with very high L/D bullets in mind. Because it is the whole point. So of course they are less likely to run into issues with accuracy.

But none of this is particularly relevant to a hypothetical military cartridge since it is not a difficult issue to anticipate or solve - the whole topic is much less complicated than you are implying.

[Triplebaconation]

"A small ammunition can filled with sand."

Obviously a sandbag is a very substantial amount of sand. And poorly packed sandbags I have seen heavier rounds go through, mostly inbetween the cracks of the sandbags, so two is usually used, but one is sufficient if, well packed.

Yes a small ammunition can, probably about 3-5 inches thick, packed full with sand. It is basically a metal sand bag.

Sand is a very good barrier against high velocity rounds, particularly when combined with heavy gauge steel. 9mm might get through though.

[United Earthlings]

Trying to decide on which design path to pursue for a mid 1930s 35,000 ton battleship, more specifically one to be laid down sometime in 1936.

If anyone is familiar with Freidman’s U.S. Battleships, was thinking of going along the lines of something like the 1935 Design Scheme 2 of the North Carolina [NC] design with nine 14in guns in three triple turrets and 30 knots speed. I figured this would be a good design framework to work from to counter vessels similar to the RL Scharnhorst-class battleship nations would be building in the AU my nation exists in.

Furthermore, hindsight being 20/20, the long hull NC designs with 30 knot speed would probably make better Carrier Escorts than the NC class did historically. Gun engagements being of limited value going into the 1940s, having 14in guns in lieu of 16in guns doesn’t seem like much of a loss of capability. Especially considering for context, in this AU my nation never officially signed its facsimile of the Washington Naval treaty, though eventually it did agreed to adhere to the terms after much local and international pressure, therefore the Commonwealth Navy has a much more advanced battle line then the United States ended up having historically, having commissioned by 1922 several 25 knot class Dreadnoughts armed with twelve 16in guns and a class of four battlecruisers armed with 14in guns and capable of 30 knots. The Design Scheme 2 of the NC class also seems to better fit the design traditions of my AU nation for what it’s worth.

On the other hand, a 28 knot battleship is still pretty fast, especially for one armed with 16in guns.

---

Speaking of Bullpups and firearms, this is the path I’m thinking of going down for the Commonwealth Army.

Having stressed long range engagements, the Commonwealth standardized on the 7.62mm NATO round throughout the rest of 20th century starting Mid-Century and into the early 21st century having never adapted the 5.56mm NATO round. Beginning in the late 1990s and early 2000s, the Commonwealth began to revaluate its tactical doctrine. Noticing two key trends developing, one, that with the world every year becoming even more urbanized that, two, the majority of small arms engagements were taking place well within 300 meters or less. An area of engagement where the benefits of the 7.62mm NATO round weren’t as beneficial, which noted by the Commonwealth had induced other foreign militaries into adapting ever more carbine type rifles like the M4.

Loathe for a myriad of reasons to adapt the 5.56mm NATO round, the Commonwealth Army bureaucrats took what some regarded at the time as an odd route by adapting an existing cartridge, that being the 5.7×28mm which was already in widespread service with the Commonwealth Army in use with its standard side-arm pistol the type Five-Seven and the P-90 PDW.

By modifying the P-90 into an assault carbine, the Commonwealth Army had itself an effective CQB carbine rifle like the M4 and others, but that was able to use the existing logistical infrastructure. Around the same time, the 7.62mm NATO round would continue to see widespread service by being adapted for use into a light SAW machine gun as the basic fire support of the Commonwealth infantry squad with generally 2 sometimes 1, 7.62mm SAWs assigned to each squad.

[Triplebaconation]

That's pretty silly.

[The Manticoran Empire]

Trying to decide on which design path to pursue for a mid 1930s 35,000 ton battleship, more specifically one to be laid down sometime in 1936.

If anyone is familiar with Freidman’s U.S. Battleships, was thinking of going along the lines of something like the 1935 Design Scheme 2 of the North Carolina [NC] design with nine 14in guns in three triple turrets and 30 knots speed. I figured this would be a good design framework to work from to counter vessels similar to the RL Scharnhorst-class battleship nations would be building in the AU my nation exists in.

Furthermore, hindsight being 20/20, the long hull NC designs with 30 knot speed would probably make better Carrier Escorts than the NC class did historically. Gun engagements being of limited value going into the 1940s, having 14in guns in lieu of 16in guns doesn’t seem like much of a loss of capability. Especially considering for context, in this AU my nation never officially signed its facsimile of the Washington Naval treaty, though eventually it did agreed to adhere to the terms after much local and international pressure, therefore the Commonwealth Navy has a much more advanced battle line then the United States ended up having historically, having commissioned by 1922 several 25 knot class Dreadnoughts armed with twelve 16in guns and a class of four battlecruisers armed with 14in guns and capable of 30 knots. The Design Scheme 2 of the NC class also seems to better fit the design traditions of my AU nation for what it’s worth.

On the other hand, a 28 knot battleship is still pretty fast, especially for one armed with 16in guns.

In terms of battleship design, a lot of it depends on what your potential enemies are.

[Purpelia]

Trying to decide on which design path to pursue for a mid 1930s 35,000 ton battleship, more specifically one to be laid down sometime in 1936.

If anyone is familiar with Freidman’s U.S. Battleships, was thinking of going along the lines of something like the 1935 Design Scheme 2 of the North Carolina [NC] design with nine 14in guns in three triple turrets and 30 knots speed. I figured this would be a good design framework to work from to counter vessels similar to the RL Scharnhorst-class battleship nations would be building in the AU my nation exists in.

Furthermore, hindsight being 20/20, the long hull NC designs with 30 knot speed would probably make better Carrier Escorts than the NC class did historically. Gun engagements being of limited value going into the 1940s, having 14in guns in lieu of 16in guns doesn’t seem like much of a loss of capability. Especially considering for context, in this AU my nation never officially signed its facsimile of the Washington Naval treaty, though eventually it did agreed to adhere to the terms after much local and international pressure, therefore the Commonwealth Navy has a much more advanced battle line then the United States ended up having historically, having commissioned by 1922 several 25 knot class Dreadnoughts armed with twelve 16in guns and a class of four battlecruisers armed with 14in guns and capable of 30 knots. The Design Scheme 2 of the NC class also seems to better fit the design traditions of my AU nation for what it’s worth.

On the other hand, a 28 knot battleship is still pretty fast, especially for one armed with 16in guns.

Speed is nice. But its not going to do you much good if you can't pierce your enemies armor. So unless your enemies do not have any modern battleships or are just generally deficient going the 14 inch route is not a good idea.
On that note the Scharnhorst and indeed German ships of the period in general are not a good thing to look at for inspiration because they simply weren't designed very well. After WW2 Germany was forbidden from building ships so when they finally restarted in the 30's they literally had to relearn everything. That's why you get ships that offer comparable or worse performance than their competitors at a much greater overall tonnage.

Really, if you want to design good ships in that period I would suggest looking at the Japanese, British and to a lesser extent the Americans.

Also, if you are into ships and want to lose your life on youtube here is a link you might like: https://www.youtube.com/user/Drachinifel

[Bears Armed]

Manokan if you were in charge we would still be in the 1914 mindset of assuming 2,000 meter combat ranges, and have some 10 by 70 mm in a bullpup by now whose ballistics are superb ballistically but utterly useless tactically.

Apparently western forces have had some problems in Afghanistan during this century because some members of the pro-Taliban (or just anti-outsider) groups were still using old rifles which did have that sort of capability and could thus -- at least in relatively open areas, or firing down from mountainsides -- out-range the westerners...

[The New California Republic]

Manokan if you were in charge we would still be in the 1914 mindset of assuming 2,000 meter combat ranges, and have some 10 by 70 mm in a bullpup by now whose ballistics are superb ballistically but utterly useless tactically.

Apparently western forces have had some problems in Afghanistan during this century because some members of the pro-Taliban (or just anti-outsider) groups were still using old rifles which did have that sort of capability and could thus -- at least in relatively open areas, or firing down from mountainsides -- out-range the westerners...

The Soviets had major issues with Lee Enfield-armed Mujahideen snipers. The Soviets had to counter the threat by tripling or even quadrupling the number of Dragunov-armed snipers assigned to each unit.

[Triplebaconation]

The Taliban generally weren't capable of effective long-range fire. They were largely limited to harassment because closing was suicidal, and these tactics were really only effective in combination with mines or IEDs.

[Spirit of Hope]

Manokan if you were in charge we would still be in the 1914 mindset of assuming 2,000 meter combat ranges, and have some 10 by 70 mm in a bullpup by now whose ballistics are superb ballistically but utterly useless tactically.

Apparently western forces have had some problems in Afghanistan during this century because some members of the pro-Taliban (or just anti-outsider) groups were still using old rifles which did have that sort of capability and could thus -- at least in relatively open areas, or firing down from mountainsides -- out-range the westerners...

Worries over the insurgents outraging coalition countries is rather overstated. The simple fact is that 5.56 is quite capable out to 500 meters, and very few people are actually good enough shots to accurately hit anything at that range in combat conditions, no matter what they are shooting.

Even in Afghanistan most direct fire engagements happened at less than 300 meters. There were some issues with long range harassing fire, but that was less the issue of soldiers being hit and more the issue of them not wanting to take chances when under fire of any kind.

[United Earthlings]

In terms of battleship design, a lot of it depends on what your potential enemies are.

That's the rub, being splendid neutral isolationists does have its disadvantages. No one power or alliance bloc is a direct threat while at the same time any Great Power is potentially an enemy. That reality tends to send naval strategy and planning in all directions, so as a design guide that doesn’t work. Which is while, Commonwealth ship designs tend to express a balance in design in so far as what’s within the technological limits of the stated time period. If that’s not possible, then the Commonwealth simply builds more naval vessels of similar types to fulfill specific roles. For example from my WIP on my nation’s early 20th century cruiser force development, one armoured cruiser class would be built that prioritized long range endurance and speed, another different armoured cruiser class built during the same time period would stress firepower and protection.

TL;DR: Every nation and no nation is a potential enemy, therefore not a useful metric to use when approaching battleship design for my nation.

Speed is nice. But its not going to do you much good if you can't pierce your enemies armor. So unless your enemies do not have any modern battleships or are just generally deficient going the 14 inch route is not a good idea.

Not necessarily, factor in that if a nation went down the 14in line with their 1910s dreadnoughts, by the mid-1930s the 14in gun would be on the majority of vessels that constitute that nation’s battleship line. Therefore, this fact would have encouraged those nations to further improve not only their 14in guns, but the ammunition they fired and as we saw historically, the introduction of Super-Heavy shells for 14in guns.

A Super-Heavy 14in shell can cause a lot of damage even if doesn’t outright penetrate an enemy battleships armor, then again one can always fire more shells at the target until you do pierce your enemies armor.

So, while yes, I agree with you a 16in gun has better penetration capabilities, a 14in gun is no slouch either. That’s not the issue though.

On that note the Scharnhorst and indeed German ships of the period in general are not a good thing to look at for inspiration because they simply weren't designed very well. After WW2 Germany was forbidden from building ships so when they finally restarted in the 30's they literally had to relearn everything. That's why you get ships that offer comparable or worse performance than their competitors at a much greater overall tonnage.

Not inspiration, the word I was thinking of was more Competition.

Really, if you want to design good ships in that period I would suggest looking at the Japanese, British and to a lesser extent the Americans.

Oh I have, even for designs that weren’t built historically, but I probably figured would exist in some form in the AU my nation co-exists in. So starting with the Japanese, you of course have the Kongo class battlecruisers and the fast Nagato-class battleships/dreadnoughts, but add in the potential for things like the Amagi Class battlecruiser and Tosa-class battleships.

For the British, you start with the QEs and Revenge class battleships followed by Renown and probably more than 1 Admiral class battlecruisers followed by a few of some form of the G3s battlecruisers. The Nelson class speaks for itself with the limitations that were imposed on its design. The next British battleship design that wasn’t so limited speaks to what a good 14in gun fast battleship design is capable of, which is a sort of counterargument against your opening point about the deficiencies of 14in guns.

Since, I’ve been following the American battleship design linage for the most part, for my nation it’s probably more extent.

I would also be remiss if without mentioning the French and Italian lines, at least in passing, but neither really matched the requirements of design I’ve been pursuing for the Commonwealth Navy.

Also, if you are into ships and want to lose your life on youtube here is a link you might like: https://www.youtube.com/user/Drachinifel

Your way late to the party with your warning, I needed you 45 drydocks and countless specials ago.

[Danternoust]

Yes a small ammunition can, probably about 3-5 inches thick, packed full with sand. It is basically a metal sand bag.

Sand is a very good barrier against high velocity rounds, particularly when combined with heavy gauge steel. 9mm might get through though.

The sand should be mixed with something... to produce an aggregate... so that the sand doesn't pour out.

[Manokan Republic]

The issue is it fits within the realms of what people normally use, intermediate to full sized rifle levels of power. The 7.62mm bullets have to be too big and the 5.56mm are too small or ineffective. The 6mm to 6.5mm is around perfect, and a number of studies, tests, and of course anecdotal pieces of evidence bear this out. It's not that 6mm round are magic, it's that on average, they tend to be more accurate and more aerodynamic for their given size. 6mm rounds are generally more accurate, although this has more to do with bore chamber dimensions than anything else, which again are well suited for cartridges of that power level. People just don't use .300 win mags or 5.7mm rounds as primary combat rounds.

It might be worthwhile double-checking. 7.62-mm VLD bullets with ballistic coefficients equal or better to common 6.5-mm VLD loadings are available in the 175-185 grain range. No heavier than common 7.62-mm loadings. There is nothing about the 6-mm calibre which makes it more accurate inherently either. There are particular cartridges like the 6-mm PPC that are especially accurate, but this is not some magic property that is conferred on every cartridge with a bullet 6 or so mm in diameter.

The issue with bullets that are too long being unstable doesn't really come up much, because few bullets are made that long, but there is an inherent instability issue. The .22 winchester, a .308 winchester magnum round necked down with a .223 sized bullet, had pretty bad stability, so much so that past 200 yards it was pretty difficult to use. A lot of these really ultra lightweight high velocity rounds tend to tumble quickly, and really long bullets have a similiar problem. Quick wikipedia thing: "For best performance, the barrel should have a twist rate sufficient to spin stabilize any bullet that it would reasonably be expected to fire, but not significantly more. Large diameter bullets provide more stability, as the larger radius provides more gyroscopic inertia, while long bullets are harder to stabilize, as they tend to be very backheavy and the aerodynamic pressures have a longer arm ("lever") to act on. The slowest twist rates are found in muzzleloading firearms meant to fire a round ball; these will have twist rates as low as 1 in 72 inches (180 cm), or slightly longer, although for a typical multi-purpose muzzleloader rifle, a twist rate of 1 in 48 inches (120 cm) is very common. The M16A2 rifle, which is designed to fire the 5.56×45mm NATO SS109 ball and L110 tracer bullets, has a 1 in 7-inch (18 cm) or 32 calibers twist. Civilian AR-15 rifles are commonly found with 1 in 12 inches (30 cm) or 54.8 calibers for older rifles and 1 in 9 inches (23 cm) or 41.1 calibers for most newer rifles, although some are made with 1 in 7 inches (18 cm) or 32 calibers twist rates, the same as used for the M16 rifle. Rifles, which generally fire longer, smaller diameter bullets, will in general have higher twist rates than handguns, which fire shorter, larger diameter bullets."

Correct twist rates for stabilization of a particular bullet is not difficult to determine for those with the appropriate knowledge. If a decision was made to move to a cartridge with very long, low drag bullets as a standard the correctly rifled barrels could be supplied. That a bullet won't be stabilized properly by an incorrect rifling twist is about as profound as the finding that it won't be sealed properly in an incorrectly sized bore.

If a particular bullet is unstable in flight this is a problem of the gun not the cartridge and certainly not the calibre. A lot more people play around with different cartridges more than different rifling twists, because most people don't bore their own barrels, but the fact they tried to fire a bullet down a barrel that was not appropriately rifled to stabilize it says nothing about the cartridge.

While we rarely see bullets that are this unusually long, and thus have these problems, it's the reason why few .223 rounds designed to fill the same niche as the 6mm and 6.5mm bullets exist. Yes in theory you could do it, but it's much harder to pull it off. The twist rate would need to be unusually fast, and most really long bullets, like say a dart round, have their own stabilization methods instead, such as fins. "Extremely long projectiles such as flechettes may require high twist rates; these projectiles must be inherently stable, and are often fired from a smoothbore barrel." This is why a 6mm or 6.5mm is usually ideal for those selected criteria. 5.56mm is just generally too smol to really be effective at those weights and energy levels, unless the bullet is so long it becomes fairly unstable. The 5.6mm GP90 from the Swiss kind of illustrates this issue, being insanely accurate at close range, with .72 MOA for their standard assault rifle, achieved through a barrel twist of 1 in 12 (vs. 1 in 7 for most military barrels) and bullets optimized for it, but the rounds destabilizing quickly at 300-400 yards sort of mitigates their effectiveness. "The required accuracy for Gw Pat 90 ammunition out of factory test barrels is 63 mm (0.72 MOA) for 10 rounds (100% radius measurement method) out to 300 m." This comes at the cost of reduced stability, and thus reduced long range performance. Without getting in to rocket science territory, the 6mm and 6.5mm are ideal bullet sizes for 1000 meter ranges and moderate sized bullets, between an intermediate and rifle sized cartridge. It's not magic, it's just the ideal bullet size for most practical military purposes. At least according to my opinion and various military studies. Some of this is subjective in nature, and intuitive, but other elements have a more concrete base to them. Hypothetical capabilities and practical capabilities are two different things.

As I already told you there is a length:diameter limit on spin-stabilized projectiles. But ALL spin-stabilized bullets exist within this limit by necessity, because aerodynamic forms are scaleable. This isn't even close to rocket science though it might be news to mall cops who "know about calibers".

A high L/D .223 or .308 bullet is perfectly accurate if it is fired out an appropriate weapon with the correct rifling twist, headspacing and whatnot. The only reason they would into issues is if they are fired out of rifles which were never meant to fire cartridges with such long bullets loaded into them, they hand loaded them badly, or both. And quite often this is going to be what is happening because people tend to be lazy and cheap - blame "unstable calibres" when you CBA to figure out the correct twist rate or botched the seating. Since chances these days are anyone firing 6.5-mm grendel or even danker 6-something mm "optimum" caliber cartridge bought an AR-upper expressly to fire 6.5-mm Grendel chances are that upper was already made with very high L/D bullets in mind. Because it is the whole point. So of course they are less likely to run into issues with accuracy.

But none of this is particularly relevant to a hypothetical military cartridge since it is not a difficult issue to anticipate or solve - the whole topic is much less complicated than you are implying.

Yes I'm aware of all of this. In existing rifles the 6mm and 6.5mm rounds make ideal bullet sizes, and for their respective weights/recoil forces. That's why I said it's more practical rather than perfect, my whole point is I'm not trying to make the best round, just something that would fit in an Ak or AR-15 easily. Hence why the 6mm PPC would go well in an Ak, responding to the guy's previous point. I wouldn't recommend designing a whole new cartridge from the ground up if your intent is to keep a weapon with as few change as as possible. Another thing to bear in mind is that while you could make a 7.4mm bullet, a 7.8mm bullet, or a 6.4mm, 6.6mm etc., going with already well established cartridges like 6mm and 6.5mm is easier since lots of bullets in those calibers already exist and their ballistics are well known. 6.5mm is chosen arbitrary from 6.6mm for example, but since it's already in mass production it's smarter to go with it.

The irony of all this is that people said I'd choose a round with great ballistics but that was terrible in automatics, and it's actually the opposite, I'm not going for the best just good. The 6mm and 6.5mm are ideal for existing weapons. If you go way out of your way, in theory other options exist. In fact, I made a list of cartridges and their respective BC's some type ago (however, the link is broken). For the ideal chamber dimensions that lead to accuracy, and to fit in existing rifles, 6mm and 6.5mm rounds are ideal, and due to recoil levels. The most aerodynamic 7.62mm round I can find that is practical for it's given length is about 15 grams, and it has .8 BC, vs. .71 BC for a 6.5mm round at 10 grams. The thing is for the same velocity, a 6.5mm kicks like a .308, vs. a .300 wing mag for the 7.62mm. I realize it's probably more aerodynamic, but it's too big. Similarly a 5.56mm would be too high velocity at rifle energy levels. For a lower level intermediate cartridge, a 5.56mm round would actually be pretty good, getting up to 6 grams before becoming too long to be realistically stable. Most of this is based on sierra match king's load-outs, whom the military copies frequently, with the blackhills ammunition being based on the sierra match king 77 grain round. These rounds are also very expensive. A 6mm or 6.5mm is around the right blend of cost and effectiveness, and fits in existing rifles with relative ease. There are 6.5mm grendel Ak's and AR's for example, and 6mm one's in various calibers. For a quick caliber conversion, you can just swap out an upper receiver in AR-15 and even use the same magazines, so these calibers seem reasonable. To convert a Tavor to 6.5mm grendel would only take some minor changes, vs. some brand new cartridge with a whole new case and everything. This is a key advantage. Again my goal is not to be too fancy. Super high end armor piercing depleted uranium saboted sub-caliber SLAP 5.56mm, 7.62mm round are bad-ass and alllll buttttt... uh, you know just unreasonable. 3 dollars a round gets to a point of silliness.

[Manokan Republic]

"A small ammunition can filled with sand."

Obviously a sandbag is a very substantial amount of sand. And poorly packed sandbags I have seen heavier rounds go through, mostly inbetween the cracks of the sandbags, so two is usually used, but one is sufficient if, well packed.

Yes a small ammunition can, probably about 3-5 inches thick, packed full with sand. It is basically a metal sand bag.

Well 2 inches thick, but yeah 3-5 inches is possible. That isn't a whole lot of sand, as most sand bags are like 12 or more inches wide, that is military sand bags, vs. civilian sand bags which are often smaller. To be fair passing through different mediums is hard for a bullet, which will deform and fragment on the metal, then be broken up in the sand, then have the fragments caught by the other side of the metal. Car doors are known to stop 5.56mm rounds and even greater, simply because the rounds will tumble and fragment, breaking up in to smaller pieces, and this keyholing/sort of shotgun effect leads to it being stopped by the second car door when spaced that far apart. But the point is it's not all that much sand, since the round is lightweight and high velocity is disintegrates quickly. Another example is how rapidly it fragments in water, vs. the Ak which travels a longer distance. The main problem with a 5.56mm is the high velocity and low weight; some newer rounds are also better at penetrating barriers like sand, so it doesn't hold true with all rounds, just M855 ball ammunition. But the point is it kind of is deficient in penetration. Wood, concrete, and even minor threats like glass are very well known to stop it. Heavier calibers are better in cluttered areas, with lots of trees or buildings or what have you, urban or jungle environments. Sand is good for stopping all manner of bullets, but especially high velocity one's.

[Spirit of Hope]

Yes a small ammunition can, probably about 3-5 inches thick, packed full with sand. It is basically a metal sand bag.

Well 2 inches thick, but yeah 3-5 inches is possible. That isn't a whole lot of sand, as most sand bags are like 12 or more inches wide, that is military sand bags, vs. civilian sand bags which are often smaller. To be fair passing through different mediums is hard for a bullet, which will deform and fragment on the metal, then be broken up in the sand, then have the fragments caught by the other side of the metal. Car doors are known to stop 5.56mm rounds and even greater, simply because the rounds will tumble and fragment, breaking up in to smaller pieces, and this keyholing/sort of shotgun effect leads to it being stopped by the second car door when spaced that far apart. But the point is it's not all that much sand, since the round is lightweight and high velocity is disintegrates quickly. Another example is how rapidly it fragments in water, vs. the Ak which travels a longer distance. The main problem with a 5.56mm is the high velocity and low weight; some newer rounds are also better at penetrating barriers like sand, so it doesn't hold true with all rounds, just M855 ball ammunition. But the point is it kind of is deficient in penetration. Wood, concrete, and even minor threats like glass are very well known to stop it. Heavier calibers are better in cluttered areas, with lots of trees or buildings or what have you, urban or jungle environments. Sand is good for stopping all manner of bullets, but especially high velocity one's.

Most things that are going to reliably stop 5.56 are going to be pretty good at stopping heavier rounds as well. Yes occasionally 5.56 rounds will be stopped by lighter barriers, but if you look at how the 5.56 preforms on average it is more than adequate for shooting people and through most things. Barrier penetration is nice, but if you make your round heavier to better penetrate then you are carrying less ammunition for the same weight. Since most rounds don't hit people, much less most rounds trying to punch through barriers, most armies have agreed it is better to have more ammo than to have marginal improvements in barrier penetration. If you want to have a heavier round feel free, but it comes at a cost of less ammo.

I'll happily say I use a 7mm projectile in NS for my GPMG, though I cheat and use ceaseless ammo.