My vast rifle experience: A few times with the powerful ancient Savage .22 single-shot over 20 years and then several well-briefed missions (with no air support) against dangerous, empty Tropicana juice jugs using my new store-bought M-1 Carbine... until it broke after two months and was sent back to the (Kahr) factory.
Pardon me for quoting from a book here, the "The Great Book of Guns", by Chris McNab, Thunder Bay Press. Found it at Borders Books in December.
There are full pages dedicated to Fabrique Nationale, the Garand in WW2, the Ak-47 and the M-16 in Vietnam etc.
"The list of guns produced by FN (Liege, then Herstal Belgium) before 1949 includes the Browning Hi-Power 9 mm handgun, the B. M1917, M1919, and M2 machine guns; the Browning BAR; and the Mauser Mle 1924 rifle. Even 40mm Bofors were manuf. from 1936 on". I can imagine some of you now
Now a pertinent quote from a section (p. 313), "The Switch To Small Caliber", about going from 7.62 to 5.56: about the 7.62 " It generated heavy recoil forces, making it unsuited to three-round burst and full-auto fire in an assault rifle, extending the training times required...".
"The most important factor in the debate, however, is that any bullet must hit a vital physical structure to guarantee a kill on a human target; cavitation or physical shock are not sufficient in themselves". His description of the SS109 (M-16) round: "The takedown power is ensured if a vital area is struck".
I know little about guns, but the book is quite interesting and informative for a novice (trying to play 'catch-up'), but not as much as your real-world debate. I would like to find a page on the Internet which has clear pictures of vital gun components in semi-automatics (Ruger Mini, M-1 Carbine) such as the extractor, various parts of the action, gas tube etc in order to find out exactly where they are and what they look like
(hint, hint).
My ignorance is quite vast, but I am only recently so enthusiastic about military rifles. A German friend (has a very reliable Colt AR-15 and a Walther [he is from Essen but has no Ger. rifles]) and my wife are surprised by it.