I have been lurking for awhile, so I figured I would join the fun :-)
I bought a bushmaster 9mm carbine approximately three months ago, and I love the gun, but I have two issues.
The first issue is that the promag that ships with the gun is just not durable. I have around 500 or so rounds through this gun (win white box, remington, etc) and have already cracked the feed lips on the magazine. While I realize this is not bushmaster's fault, I can see myself spending alot on mags (modified uzis, colts, etc) since the promags just don't cut it. Then again, I guess promags are twenty dollars or so, and colts are fifty dollars each on a good day.
The second issue I have is that since this rifle works perfectly right out of the box (no mag blocks, etc) I would love to sbr it and attach the factory pistol upper that bushmaster uses on their carbon 9mm pistol. However, after 3 calls to bushmaster and an email they refuse to sell me a carbon 15 9mm pistol upper for this rifle. It is not that I want to have it in my possession before I get the stamp from atf, but I would like to know that I can get the part that I need from bushmaster if I go through thr trouble of spending the 200 dollars and the time, effort, etc to sbr the rifle.
The bushmaster rep did say that any ar 9mm upper will work on this lower, but I would like the upper and lower to match (both carbon).
So that is my two cents. Hoefiully someone can benefit from a first time poster but long time lurker :-)