Not sure wounding vs. killing was the big differentiator. As tptacek mentions, any non-trivial rifle-calibre hit is incapacitating. What determines whether the

Not sure wounding vs. killing was the big differentiator. As tptacek mentions, any non-trivial rifle-calibre hit is incapacitating. What determines whether the victim dies immediately or has a chance to survive depends on where it hits. The big things, as you mention, was that real life engagement ranges were considerably shorter, so you could sacrifice long-range performance and gain lighter weight (allowing the soldier to carry more rounds) and making the thing somewhat controllable on full auto for close-quarter fighting. The Germans figured this out, and towards the end of WWII they fielded the "Sturmgewehr 44 (Stg 44)". This fired a shortened version of their standard rifle calibre round (7.92mm). The Soviets did the same with their Ak-47 family. The price of keeping the full rifle caliber but slow round (around 700 m/s muzzle velocity) was poor ballistics and armor penetration. Later on the US went to the other extreme with a very small caliber firing at higher than usual rifle muzzle velocity (almost 1000 m/s). Ironically there was research going back all the way to pre-WWII times suggesting the "optimal" infantry caliber would be somewhere in the 6-7mm range with muzzle velocity in the "standard" range for rifles (around 800-900 m/s).