The standard magazines has capacity of 30 rounds, it deals normal damage.
The high capacity
the high capacity magazines has minimum 50 round and maximum 100 rounds. the high capacity mags are best if you want make lmg since its damage is not that high, the max damage ranges from 4-6 damage per shot, but if you hit the target in the head it should deal +2 more damage.
The shell loading
The shell loading are usually for shotguns or guns with a scatter barrel, but it can be used for burst weapons too.and has up to 15 rounds if its used with any barrel other than the scatter, if you use the scatter you only have 8 rounds for making it balanced. The shells deals up to 45 or more damage if it used with a scatter .
The bolt action.
The bolt action is only useful for very high-damaging weapons or snipers. The bolt action is not useful for any weapons other than semi auto weapons, because when you shoot you have to pull the bolt back. It deals from 13 damage to 50 or 70. You can get one shot kills on the targets but it has to be a headshot and the enemy must not be overhealed.