I have a lot of time behind short M-16s and SBRed AR-15s. Of all of them, the shorter than 10 inch guns suck to shoot in 223. Too much noise and harsh recoil make them not a lot of fun to shoot. 11.5 - 12 inch rifles with carbine gas are the best. And there isnt a lot of suppressors that will warranty their cans when shot on anything shoter than 11.5 inches.

300s down around 8-9 inches with a short can are a lot of fun to shoot and run well. Get into reloading and you will be able to shoot more. You wont save any money, but you will be able to afford to shoot almost twice as much.