M822, optimized for penetration to meet a NATO requirement to penetrate a steel helmet at 800 meters. Contrast that with well noted damage caused by M193 ball in RVN.
The Russian 5.45 has a long for caliber bullet with an aft CG to promote yaw and tumble. An idea the British put to good use in MkVII ball in 1910. As soon as the bullet hit the target and decelerated, its heavier lead base caused it to yaw violently and deform, thereby inflicting more severe gunshot wounds than a standard single-core spitzer design.
Like anything else, bullets are a compromise, "pays yer money and takes yer choice."
As originally intended in the 20” M16 and M16A1 M193 ball ammunition would tumble and fragment at ranges up to 200 meters. It had a fragmentation threshold of 2600 fps, so the shorter the barrel the shorter the fragmentation range, dropping to 150m from a 16” carbine to 100m in a 14.5” barrel and to down around 50m in an 11.5” barrel.
The fragmentation velocity for the M855 ball round was the same 2600 fps. Unfortunately in a 20” M16A2 it had a muzzle velocity that was slower (3130 fps versus 3280 fps). That reduced the fragmentation range to 150 meters.
Problems with it boring nice clean .224” holes were noted in the gulf war.
Then the M4 was adopted and reduced the muzzle velocity of M855 to 2920 fps. That reduced the fragmentation range to 100m, half that of M193 in the M16A1.
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Interestingly people think the concept of fragmentation and tumbling to increase lethality came along with the 5.56 NATO. But if you dig into old ordinance records you’ll find that was a primary argument for adopting the .30-40 Govt round over the .45-70. The lighter, smaller but much faster diameter Krag round was presented as being more lethal as it would tumble on impact.
The later spitter rounds increased this effect by retaining more velocity as well as having a pointy tip that was less stable post impact.
The British did extensive research prior to WWI and determined .276” was the best diameter for a battle rifle round to optimize the velocity and tumbling effects. Had WWI not intervened, they would have adopted a .276” round in the Pattern 13 Enfield rifle. With WWI looming the plan was delayed as they did not want two service rifles and cartridges in the supply chain, although they did acquire the Pattern 14 in .303 British as an alternate standard rifle. After WWI the conversion plan was scrapped as they had a massive surplus of .303 ammunition in stock and plenty of SMLE rifles.
Between the wars the US Army was interested in adopting a .276” round in the form of the .276 Pedersen in the M1 Garand, however large existing stocks of .30-06 ball ammunition resulted in the conversion of the Garand design to fire the .30-06.
After WWII the .280 British cartridge reflected the intention to use a .276 diameter bullet (now expressed as the larger groove diameter rather than land diameter).
