The G3 rifle in the game has 3 possible uses.

1. A low damage Assault rifle.
2. A medium damage Assault.
3. A DMR.

Apparently, using the option for 1 is the one of the worst choice any heister can make because the ammo pickup rate isn't buffed to match the other ARs of this category not to mention the tiny magazine size of 20 rounds which makes it very difficult to use (Yes I know the AS VAL also has a 20 round capacity).

This mod increases the magazine size to 30 rounds, leaving more room for the user to be forgiven, and increases the pickup to 5 ~ 8.75 which is marginally better than the other guns of this category without Walk-in closet (The M4 has 4.5 ~ 8.25 pickup) but objectively worse when Walk-in closet (6.08 ~ 11.14) or Fully loaded (7.88 ~ 14.44) is taken into equation because this gun cannot receive those effects.

(It also clears up the code a bit for the DMR kit but it doesn't have any effect for the performance of the DMR itself. Only there to let the Assault Kit have increased ammo pickup)