Put your brain past the ridiculousness of this; the idea is that one rifle can carry both short and long .223 rounds. The clips both feed into a single barrel and the user can switch between the two on the fly. One is for long range assault, the other for close range spray.
Here are some of the roughs i was working on to get to this point. There are a few more that I may post later. I am also working on a sniper type gun.