WI: 7.62x51mm never becomes NATO standard

It's probably balancing the ability to penetrate armor with wounding capability. If the .256 is causing more wounding than a larger caliber bullet, it's probably fragmenting.
Or loosing velocity inside the body at a greater rate and transferring more energy to tissue.
 
Perhaps the Germans make greater use of the 7.98 Kurtz - perhaps an earlier STG44 introudced in much larger numbers and generally picked up by allied soldiers
Perhaps Hitler doesn't interfere and the sniping/bayonet/rifle grenade requirements are dropped and the MKb42 is standardised?
 
And the only way to do that is by tumbling, fragmenting, or expanding.

Fragmenting and expanding are out from Hague regulations, so you have FMJs
You can play with really thin jackets, or what the US did with the 5.56mm, and bare stabilize the bullet with a slow rifling twist.
That effects accuracy, so it's a tradeoff. The US started with 1:14", and is now at 1:7" The bullets don't tumble anymore, but they can hit and then penetrate a helmet at 400M
 

Deleted member 1487

Fragmenting and expanding are out from Hague regulations, so you have FMJs
You can play with really thin jackets, or what the US did with the 5.56mm, and bare stabilize the bullet with a slow rifling twist.
That effects accuracy, so it's a tradeoff. The US started with 1:14", and is now at 1:7" The bullets don't tumble anymore, but they can hit and then penetrate a helmet at 400M
The twist rate isn't an issue in terms of the M193 round and fragmentation/tumbling. It was fully stabilized by the slower twist because it was a shorter, lighter bullet. The modern bullets are longer and heavier so to stabilize they require a faster twist as did shortening the barrel in the m4 carbine which prevented twist from being imparted more gradually:
https://en.wikipedia.org/wiki/5.56×45mm_NATO
The earlier 5.56 rounds (M855/SS109 and the original M193) were optimized for a 20-inch (51 cm) barrel with a 1:12 twist. The shorter 14.5-inch (37 cm) barrel of the M4 carbine (with a 1:7 twist) generates lower muzzle velocity

The tumbling was the result of being a small bullet moving very fast; beyond a certain range though the bullet loses that velocity and ice picks, that is due to moving slower it is more stable as it hits a target and just pokes a small hole. The M855 bullet that was longer and heavier with a steel tip was much more stable due to being slower than the previous bullet and being designed to penetrate body armor, so wouldn't tumble often, especially as slower speeds. The Soviets found the way to get around that speed dependency was to have a air pocket in the tip of their bullet so that when the bullet hit a target the lead/steel core would slide forward and cause it to reliably tumble very quickly at any speed.

BTW the old M193 bullet for the 5.56 ammo was always able to punch through a helmet at 400m, it was in fact designed to do so out to 500 yards.
https://en.wikipedia.org/wiki/5.56×45mm_NATO
The parameters that were requested by CONARC were:

  • .22 Caliber
  • Bullet exceeding supersonic speed at 500 yards[9][4]
  • Rifle weight of 6 lb
  • Magazine capacity of 20 rounds
  • Select fire for both semi-automatic and fully automatic use
  • Penetration of US steel helmet through one side at 500 yards
  • Penetration of .135-inch steel plate at 500 yards
  • Accuracy and ballistics equal to M2 ball ammunition (.30-06 Garand)
  • Wounding ability equal to M1 Carbine [4]

Robert Hutton (technical editor of Guns & Ammo magazine) started development of a powder load to reach the 3,300 ft/s (1,006 m/s) goal. He used DuPont IMR4198, IMR3031, and an Olin Powder to work up loads. Testing was done with a Remington 722 rifle with a 22-inch Apex barrel. During a public demonstration the round successfully penetrated the U.S. steel helmet as required.
 
Fragmenting and expanding are out from Hague regulations, so you have FMJs
You can play with really thin jackets, or what the US did with the 5.56mm, and bare stabilize the bullet with a slow rifling twist.
That effects accuracy, so it's a tradeoff. The US started with 1:14", and is now at 1:7" The bullets don't tumble anymore, but they can hit and then penetrate a helmet at 400M

If you want to be strict, designing a bullet with a very thin jacket with the intent to break up inside the body you could argue it was in breach of the hague conventions.
 

Deleted member 1487

If you want to be strict, designing a bullet with a very thin jacket with the intent to break up inside the body you could argue it was in breach of the hague conventions.
Thing is the US never signed on to that treaty. But it is the modern legal standard to accept fragmenting bullets.
 
The twist rate isn't an issue in terms of the M193 round and fragmentation/tumbling.
The first Colt barrels were in 1:14, later ones in 1:12 because in cold weather testing, 1:14 was not fully stabilizing the XM-193.

By time the M16 with 1:12 was being used in Vietnam, it wasn't performing like the earlier trials with the Green Beret advisors

less stable bullets, greater chance of keyholing and tumbling, the only way FMJs can transfer large amounts of energy to tissue, otherwise you are just drilling holes.
 

Deleted member 1487

The first Colt barrels were in 1:14, later ones in 1:12 because in cold weather testing, 1:14 was not fully stabilizing the XM-193.

By time the M16 with 1:12 was being used in Vietnam, it wasn't performing like the earlier trials with the Green Beret advisors

less stable bullets, greater chance of keyholing and tumbling, the only way FMJs can transfer large amounts of energy to tissue, otherwise you are just drilling holes.
https://en.wikipedia.org/wiki/ArmaLite_AR-15
The damage caused by the 5.56 mm bullet was originally believed to be caused by "tumbling" due to the slow 1 in 14-inch (360 mm) rifling twist rate.[29][44]:372 However, any pointed lead core bullet will "tumble" after penetration in flesh, because the center of gravity is towards the rear of the bullet. The large wounds observed by soldiers in Vietnam were actually caused by bullet fragmentation, which was created by a combination of the bullet's velocity and construction.[47][29][44]:372 These wounds were so devastating, that the photographs remained classified into the 1980s.[44]:373

https://www.ar15.com/ammo/project/Fackler_Articles/wounding_patterns_military_rifles.pdf
 
Perhaps Hitler doesn't interfere and the sniping/bayonet/rifle grenade requirements are dropped and the MKb42 is standardised?

That would work - simplify some of the issues and then modify to almost to Sten gun standards and spam them out in 43 onwards by the train load
 
And the only way to do that is by tumbling, fragmenting, or expanding.
It's more complicated than that. The energy of a bullet comes from mass and velocity. Non expanding FMJ bullets retain a constant mass, While loosing velocity If two bullets arrive with the same energy, in the lighter one a higher fraction of that energy is speed, that can be lost and liberate energy inside the body doing more damage, while in the heavier a higher fraction is mass, which is not directly turned into transferable energy. Since drag increases with speed, the lighter bullet may actually loose more energy inside the body if it's penetrating power is at the point were it is near its limit. Ideally that bullet will loose a lot of velocity while traversing the body.
Makers of hunting ammo optimise rounds for specific game (and range) by varying speed and mass, but must stay within the energy limits the round can deliver and the rifle can take.
 

BigBlueBox

Banned
It's more complicated than that. The energy of a bullet comes from mass and velocity. Non expanding FMJ bullets retain a constant mass, While loosing velocity If two bullets arrive with the same energy, in the lighter one a higher fraction of that energy is speed, that can be lost and liberate energy inside the body doing more damage, while in the heavier a higher fraction is mass, which is not directly turned into transferable energy. Since drag increases with speed, the lighter bullet may actually loose more energy inside the body if it's penetrating power is at the point were it is near its limit. Ideally that bullet will loose a lot of velocity while traversing the body.
Makers of hunting ammo optimise rounds for specific game (and range) by varying speed and mass, but must stay within the energy limits the round can deliver and the rifle can take.
You're right, but still, insisting on a round that has a stable trajectory and does not fragment or expand is a severe handicap to terminal ballistics. There's a reason why police almost always use hollow points.
 

Deleted member 1487

You're right, but still, insisting on a round that has a stable trajectory and does not fragment or expand is a severe handicap to terminal ballistics. There's a reason why police almost always use hollow points.
They also do that so the rounds don't over penetrate intended targets or punch through walls and into other unintended people.
 
BigBlueBox. Is it too late to rename this thread as WI: the USA chose something other than 7.62x51mm? The posters have pretty well ignored NATO.
 

BigBlueBox

Banned
BigBlueBox. Is it too late to rename this thread as WI: the USA chose something other than 7.62x51mm? The posters have pretty well ignored NATO.
Only mods can change titles. Some of the earlier posts discuss the effects on Britain and Canada.
 
It's more complicated than that. The energy of a bullet comes from mass and velocity. Non expanding FMJ bullets retain a constant mass, While loosing velocity If two bullets arrive with the same energy, in the lighter one a higher fraction of that energy is speed, that can be lost and liberate energy inside the body doing more damage, while in the heavier a higher fraction is mass, which is not directly turned into transferable energy. Since drag increases with speed, the lighter bullet may actually loose more energy inside the body if it's penetrating power is at the point were it is near its limit. Ideally that bullet will loose a lot of velocity while traversing the body.
Makers of hunting ammo optimise rounds for specific game (and range) by varying speed and mass, but must stay within the energy limits the round can deliver and the rifle can take.


Thing is with the above, drag (in terminal ballistics) is not just a function of speed. It's also a function of the bullet itself. A bullet that's expanding, or tumbling will increase drag, a bullet that fragments and breaks apart* which each fragment itself splitting away from the initial trajectory will also have it's own drag coefficient. On top of that each of those things also increases tissue trauma in and of themselves without worrying about increasing drag.

A larger bullet will drag more as it moves through the body as drag is also effected by the cross section of the travelling object as well as it's speed. A smaller bullet might shed is velocity proportionally faster in response to drag, but a more massive bullet will still shed it's energy as well. So while mass might not directly be turned into transferred energy, a more massive bullet still increases the energy available for transferal by having more the energy available in the first place.

there's also the point that bullet mass and velocity are seldom completely separate values. (and that they also impact on other parts of the ballistic journey before terminal)!

Your basic point about getting bullet to transfer all it's energy into the target before exiting is correct, it's just that's exactly what expanding bullets were designed to help with


*which of course is more likely to happen with fast small bullets so there lots of effects going on here in both directions.
 
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Deleted member 1487

BigBlueBox. Is it too late to rename this thread as WI: the USA chose something other than 7.62x51mm? The posters have pretty well ignored NATO.
Part of the problem with the OP is that he is mandating the British .280 round, which was intended to replace all other rounds, while at the same time saying they'd maintaining a heavier round for sniper and and MG roles. If you're going to have a two caliber standard then the .280 is pointless, as it was meant to replace the .303 entirely in all roles. They'd have been better adopting a 6.5mm as rifle/lmg round and maintaining the existing .303/.30-06 standard for MMGs/sniper rifles, but instead tried to keep the one round standard and created a flawed compromise round that wasn't good enough in any role to justify it.
Certainly the .270 was a better option then the .280 if they were going to try to make a modern assault rifle, but then would have to keep a 7.62 full powered round as OP suggests, though IMHO even the .270 is overpowered/overweight for a rifle round given the knowledge gained in WW2 about engagement ranges and recoil impact on automatic fire.

Nevertheless assuming that became the NATO standard, that is the .270 with a standardized 7.62 full powered round with M1 style bullet (say something more powerful than the 7.62x51 NATO of OTL), that would have been quite a bit better than what existed IOTL. Question is whether it would be in service in time for Korea given the post-WW2 budget cuts and huge stockpiles of left over equipment that the US relied on for years after WW2. Assuming the Brits still go their way and the Canadians follow, they could well have the EM-2 in .270 for Korea (with all it's potential flaws) and beyond. Not sure if that makes any sort of difference considering their limited commitment to Korea.

In Vietnam though that might make a bigger difference if the M-14 or whatever US weapon is selected is in .270 and works well with it, especially if there is some sort of SAW variant in that caliber. It would be highly interesting if the AR-10 was in .270 and beats out or replaces the M-14. If there wasn't the burst barrel in the torture test, which might not happen given the lower pressures of the .270 round, perhaps the AR-10 might have been given a go instead of the M-14.

I cannot see the FN FAL getting adopted by the US in any circumstances given the attitudes of the day, even if or perhaps especially if the British .270 is adopted. The Brits too would probably keep their EM-2 unless it fails in the field. So the FN FAL might remain a rather small production weapon ITTL, especially if the AR-10 is a competitor.

Vietnam with the US squad standardized on the AR-10 in .270 would be pretty interesting and would have given the AKM a run for it's money.
 
@wiking sums up my thoughts on the scenario well in that last post. If NATO is to accept a two caliber arsenal, then a short 6mm-6.5mm is likely the best choice for an infantry rifle and lmg/saw support weapon, with the old .303 or .30-06 as the MMG or platoon level heavy fire support. However, if such a round were accepted I fear NATO would find itself in a situation similar to where it has been over the last 15 years or so in that the smaller high-velocity infantry round just "punches holes" instead of immediately stopping a threat.

On the other hand, if we are looking at adopting the .270 or .280 British (or similar 6.8mm-7mm round) then really we are accepting a compromise to behave as a universal round for use in the standard infantry rifles, assault rifles, and LMGs. In those circumstances the .270/6.8mm is probably the better choice. The .280 itself was a compromise proposed by the British to appease the US requirement for long range shooting (taken to the extreme of compromise with the .280/30). Modern evaluations and ballistics development have revealed that a longer and heavier .270 FMJ (in the 115gr - 130gr range, making for a very long bullet with high cross-sectional density) produces just about the perfect balance of ideal trajectory, stability, and wounding capability. As I stated in an earlier post, a mid-length .270 round--something like the wildcat .270-08, perhaps even a shade shorter like a 6.8x48mm (longer and more powerful than the modern 6.8 SPC) instead of 6.8x51mm--would probably be the best option as it allows a relatively short action for high rate of fire while also permitting 1000 yard accuracy equal or superior to the 7.62x51 NATO of OTL with the right load.

To @yulzari's point regarding the thread title, I think it is fine to keep it referring to NATO even though the discussion has largely focused on the US because NATO would have been unable to adopt any particular round without full US backing. Ultimately, for NATO to take something smaller than 7.62mm the US would have to accept something smaller than 7.62mm during the time period in question.
 
If NATO is to accept a two caliber arsenal, then a short 6mm-6.5mm is likely the best choice for an infantry rifle and lmg/saw support weapon, with the old .303 or .30-06 as the MMG or platoon level heavy fire support.
what advantage does keeping .30-06/.303 or moving to something like .280 brit/7.92* 41 have over 7.62*51?
remember that 7.62 allows the us to gain all the advantages of a lighter cartridge case while maintaining the same level of firepower in the medium/gpmg's while also maintaining most of the tooling required for the manufacture of barrels
 
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