Well, after having the carbine assembled for about a month and a half, I finally made it to the range yesterday evening. This rifle started life as a Colt 20" HBAR. When the Chief at the PD I work for finally decided to let us carry rifles, I ordered a Bushy 16" Superlight barrel for it and had a friend install it and an old 2-position collapsable stock that I already had. The HBAR was wonderfully accurate but was an absolute pig to carry for any length of time, not to mention that the 20" barrel is awkward at best in buildings and cruisers. Ammo used was some of my carefully hoarded Q3131A. Here's the good, the bad and the ugly!
The Good- This thing is light! It points and balances a LOT better than the HBAR and the weight was trimmed down by at least 1 1/2 lbs. Recoil isn't much worse than the HBAR with just a little more muzzle rise. Not hard to control at all, even in rapid fire. It functioned like a dream. After getting it sighted in, I did some plinking, then dumped 2-30rd mags through it to verify function. It ran like a top! During rapid fire (see below), the handguards dissipated heat VERY WELL! The vent holes looked like little chimneys but the handguards stayed cool to the touch.
The Bad- You guys that said that light barrels heat up fast were perfectly correct. After about 15-20 rds when I did the mag dumps, the barrel started smoking like you wouldn't believe- the Breakfree burning off the exterior of the barrel. Looked like someone had started a signal fire! A major problem was noted, also. In order to get the carbine sighted in, the rear sight had to be cranked almost all the way to the left, something like 2-3 clicks away from it's maximum travel. Likely a canted FSB although it looks straight. Anyone know a simple way to check if the FSB is canted? I'm going to have a friend shoot it before I start doing much to it and see if it's me or the carbine. It shoots to point of aim, though, so I don't think it's me.
The Ugly- MY SHOOTING! Due to ammo prices, I haven't shot any of my rifles, except a few through my MAK-90, for well over a year. It showed, too. At ~100 feet (the most I could get out of the PD's range), I couldn't keep a group better than ~5". Go on, flame away if you wish. I can't afford much ammo at current prices so practice is non-existant. A good point, though- the Chief Financial Officer (the wife to you single guys) approved the purchase and procurement of a case of Wolf if I can find any. I know, I know, it's Wolf. But at least I can get some practice in. There's no way in Hell that I can afford the good stuff right now.
One more good thing. I let my 7 year and 3 year old daughters shoot my Ruger MkII. They had a BLAST! I had to hold the pistol on target just in front of the triggerguard for the 7 year old so that she didn't launch a round over the rather short backstop and I held the pistol for the 3 year old and let her pull the trigger. Both enjoyed the experience and want to know when they can shoot again. All in all, a very enjoyable way to spend an evening with the wife and kids.
If I make it to qualifications Wednesday (I got summoned for Jury Duty this week- didn't have to appear yesterday and don't have to appear tomorrow, the way my luck runs I'll have to go Wednesday, though) I shouldn't have any trouble qualifying, even with the sight issue. The longest stage of fire is 150' and I had absolutely no trouble shooting plenty well enough to qualify at 100', just with larger groups than makes me warm and fuzzy. If I make it to qualifications, I'll wait a few weeks and see if it's me or the carbine. If I don't make it, I think I'm gonna try and have my friend shoot it this weekend then call Bushy and see if they will do anything. Either way, I'm gonna try and rectify the issue instead of living with it. We'll see how it works out.
The group sizes may not be your shooting. I have not been happy with my BM superlight as it groups 1.5- 2 inches at 25 yrds. This is after I free floated it. It is now my plinker/beater rifle.
It also sounds like your barrel might be over torqued also.