I have no idea what any of the guns you mentioned are, Todjaeger. I'm not a gun person.
I just eyeball this stuff. If it seems like really serious military hardware, I call it weapon 4. If it seems civilian-appropriate, I call it weapon 3.
The Barrets listed (M-82 and M-95) are both very large, very heavy sniper rifles, the kind known as anti-material rifles. If you've ever seen the movie "Navy Seals", the character called God used one, or something like it.
The other one I mentioned, the M-21, is basically a specialized version of an M-14 which was the commonly issued rifle the US military used after the Korean War and partway into the Vietnam War. Civilian versions of the M-14 are available, with the major difference being that they aren't capable of fully automatic fire. What made the M-21 special is that they were re-worked to make them extraordinarily accurate.
As should be obvious by now, I know a little bit about guns and military equipment. That is sort of an outgrowth from my interest in history, military history, and militaria.
The general way I deal with firearms is as follows:
'hold-out' or Derringer-style pistols, or pocket pistols in small calibres (0.22 cal. or 0.25 ACP, 0.32 ACP, etc) count as Weapon: 1
Most service revolvers and pistols are Weapon: 2, as are small calibre rifles (Ruger 10/22, etc)
Most rifles and shotguns, as well as over-sized/big game-calibre handguns (0.454 Casul, Desert Eagle chambered in 0.50 AE, etc) are Weapon: 3
I reserve Weapon: 4 for generally military-grade weapons and explosives which are designed for use vs. vehicles, people & vehicles, structures, or to conduct attacks against entire zones.
Therefore large anti-material rifles like those already mentioned are Weapon: 4
A hand grenade
40 mm grenade/grenade launcher
M2 'Ma Deuce' 0.50-cal. Browning Machine Gun
Flamethrowers
M18 'Claymore' mine
and so on...
-Cheers
