I have a carbine AR by Colt, and I want to get into 3 gun. Mine has an H bar fixed upper now, and I'd like to go with a rifle or mid length upper, 18"-20" barrel, etc. I know some guys bark at me " just buy a 3 gun rifle"... Well, I don't want to spend $1200 on a rifle IF one of mine can be converted to work as a beginner in an entry level class. Anybody done this? I know I'm limited on this stupid different pin size thing..