Human Traitor is right, but this is not everything.
"why is 9x19 guns are so underpowered?" - Why are Kalashnikovs shit in every American game?
"BlackOps SMG listed to use 5.8mm while it's clearly an MP7" - it's not an MP7 (whatever that is).
"mosin and bolt action rifle are both 30 damage" - check again. You clearly don't know the mechanics. Check again the INFO section.
"while for some reason SKS, Groza, AKSU-74 (why 74, they have AKM with folded stock (AKMS) that also uses 7.62x39 unlike AKSU-74 that fits because AKM is modernized version of AK-47) and AK-47 have the same damage value, while 7.62x39 is a much less powerful cartridge (it's an intermidiate one, so it's intended). Nato guns have magical 10% armor penetration while the real 5.56 nato is less powerful compared to the 7.62x39 and even 7.62x54R with 7.62 NATO. Same with SVD as it uses 7.62x54R." - These are never clear cut in games, but I ran it against many qualified nitpickers and the consensus was it was good enough. Also remember that many weapon types have a broad range of ammo types, so I had to pick something that worked well.
"as for groza, current description is so bullshit (also the fact that it's AIMS BETTER is not really accurate, it was found to have harder aim, but it should have better aim/less time units in auto due of balance created by bull-pup scheme and the later can be the same with all bull-pup weapons) i think you should start it with "this AKS-74U-based weapon", because it's not really an AK replacement (also it's a variant of OTs-12 Tiss), it's a gun for Spetsnaz, in 7.62x39 configuration." - I based it on Groza in ACM Mod (for UFO Aftershock). Sorry but I trust Okim more.
"As for nato guns, they kinda look weirdly balanced (m16 has the best aimed accuracy while having only aperture while it should have the best auto (x3) bursts (that's what stoner wanted it to be, really), FAMAS has the same timeunits for bursts as other rifles while having better handling due of being a bull-pup and having a higher rate of fire and also the same thing as with m16, it has aperture sights), same thing about aperture sights and optics could be said about rifles as well. Also older rifles should have less accuracy on aim due of them not having more advanced optics and the og optics are probably gone bad too due of age." - I've heard bazillion of opinions, often radically different, so I stopped giving a shit.
The truth is, I don't know much about real life weapons (or care), so my ambitions here are limited to not be blatantly stupid. Which works fairly well by now.
Also, gotta say, putting this in a bug thread was pretty cheeky...