I’ve looked all over this thing and all that I can find is this. It had a FSB on it but doesn’t currently. My best guess is that it’s from possibly a Bushmaster. It’s something that I took off years ago and like the disorganized person that I was/am but am trying to correct, I didn’t mark it in any way. If anyone ca; identify this or send me in a direction I’d appreciate it. It’s a heavy barrel with a 0.750” diameter at the FSB.

From this thread https://www.ar15.com/forums/ar-15/Bushmaster_Barrel_Marking_/118-219702/


Since the 80s, all military barrels are stamped with some variation of what you see below.  BM began marking their barrels like this when they got a small one-time supplimentary contract for M4s during Desert Shield, and were (illegally) given (by the Army) the Technical Data Package for the M4.

B MP 5.56 NATO 1/9 HBAR

B = Bushmaster  (this varies by manufacturer, of course.  C = Colt, FNMI = FN, etc.)

M = Magnetic Particle Tested (mangnafluxed)
P = Proof Load Tested

5.56 NATO = Chamber dimensions, as opposed to the tigher commercial ".223 REM" chamber

1/9 = Rifling Twist Rate.  1 turn every 9 inches.  Military barrels are 1:7, or (older) 1:12.

HBAR = Heavy Barrel, and only seen on HBAR-profile barrels

Thanks, most of the markings I knew, but the B was really throwing me off and for some reason my brain connected it to the MP even though it’s obviously spaced.

Correct, had one just like it that came in a Bushmaster pkg.

Those Bushmaster HBAR barrels were everywhere in the late 90's to early 2000s.

Yep.  Exactly what came on several batches of LE carbines that we got from BM.  

Good barrels from my experience- have plenty of complaints about those BM rifles, but the barrels/accuracy was never one of them.  I would use that barrel in a heartbeat.