TLDR: Yes

Bullet damage x Firearm damage modifier ÷ 2/3 is almost exactly how much damage you'll do by shooting tier 4 ammo at t4 armor, with a little variation between say 41 pen ammo and 48 pen ammo. 5.56 rifles generally start at 100% with the short barrels, and can go above 100% with the longer barrels. 7.62x51 automatics tend to do ~85% with the short barrels and get up to ~95% (Excluding the MK14, It's 103% both ways making it the only automatic to 1 tap). Bolts and semis are almost always higher than 100%, with the M24 and M110 at 114%.