Foxi, what I wanted to say, what was really invented after 1945?
mauser 98 - year 1898, (much before end of ww2, right? In fact even before ww1)
Doube rifles, box locks, side locks, etc... as you said
colt 1911.. before end of ww2, actually before ww1, etc
browning HP pistol - 1935?
machine gun design perfected by 1942, right before ww2. (mg42)
Automatic weopens, all kinds, all systems perfected till end of ww2.
then for gun barrel production, we have
cut rifling, since begging of fire arm manufacture.. but
button rifling, pattented by Lothar walther in twenties... between wars
barrel hammer forging, 1939- perfected till 42, probably, again before end of ww2...
double stack magazine pistol, HP35 - before start ww2
double action pistol, walther p38 - between wars
So, whatever was invented, it was invented by the end of ww2. or beter put it before end of ww2
After ww2, the design development is slowed down, all major things are already well known,
After ww2, you have:
rise of fast magnums, but it is not really new invention - before that we had 8x68, or 280 Ross, right?
We have invention of premium bullets, right, like nosler partiton? But H-mantel invented earlier, by... well, by Germans
There is slight improvement in glass and optics technology, but optics are around on guns since 19 century
What else...?
Oh, yes, modularization of guns, but take downs have been also earlier designed,
straight pull action - well, also, earlier design, some have even seen ww1 action (Ross, Smidt Rubin, etc)
The thing which is really invented in post ww2 era is piccatiny rail.
thats about it, about great designs.
As mentioned, all great gun designs are invented, before the end of ww2....in various times in history, and most of it between 1850 and 1945.