Really the only ammo that issue used that much is 9mm and 44 but 9mm has much more uses then 44. A suggestion is make a weapon mod simply called
44 receiver and the 9mm receiver
The 44 and 9mm receiver can be placed on the Tactical AR, Lever action and SMG
9mm holds more ammo but deals less damage. Adds 14 rounds for the lever action and 32 to the TAR
44 deals much more damage but damages the gun more. The lever action holds 12 and the TAR holds 25 rounds. And 20 for the SMG
It has a piercing abilities
You may say! But there is no automatic rifle that shoots 44 Adam! You stupid
My response. The game is set in the future. Maybe then someone will make ether a SMG or an assault carbine in 44. Plus saves gives more uses for other guns