Yeah, nevermind the fact that the first two Fallouts had most of the guns the 'CoD fans' want in the game. Yeah, let's just skip over that entirely to troll everyone. I'm not giving up my M1 Garand, AK47 and M2 Browning. They were in the isometric Fallouts, they're staying in my 3D ones. They're just as lore friendly as a nuclear powered bus. Oh, and let's not even meniton the M2 Browning, Thompson SMG, B.A.R, KAR-98, Mauser, etc etc being designed and built BEFORE divergence even occured, leaving those weapons to be perfectly lore friendly as well. http://fallout.wikia.com/wiki/Chauchat It didn't work in the Fallout universe, either. Technically speaking the AK47 was designed before divergence occured, not that it matters as the AK obviously existed as it was in one game and the CAR is technically an AK-112.
Oh, and just for the lulz: The fallout timeline didn't diverge that suddenly. It's not like it just e-braked onto a side-street and speed off into the sunset. No, it slowly merged off the modern timeline.
tl;dr: Not everyone wanting familiar weapons does so because they were in COD.
On a somewhat unrelated note I think I want a Chauchet to nail to my Tenpenny wall.