This will change the Large mag to a drum mag I found in the meshes that I haven't seen in-game for the combat rifle (you can tell this is not the one for the shotgun). As well as the 10mm pistol reflex that replaces the Dot reflex on the Combat Rifle. Enjoy.

Also checkout my 10mm pistol http://www.nexusmods.com/fallout4/mods/2908/

Willing to take suggestions and feel free to use this how ever you like in your own mods just let me see what you come up with.

To install it you will need to place it in Fallout 4\Data\meshes\weapons\