I just built a nice A4 type rifle using all RRA components with the exception of a brand new in wrap FNMI Govt. profile 20 in barrel. The barrel indexed nicely, gas tube alignment is suberb with no carrier key friction whatsoever when installing empty bolt carrier. Torqued according to TM with the 3X tighten loosen to 31 ft. lbs. Final torque when aligned was right near 65 ft. lbs. The end result was a very slick and excellently indexed & aligned barrel and gas tube.

I have one area of concern. The threads and barrel extension itself were properly greased with Moly B, but it was a very tight fit when inserting the barrel extension into the receiver. I heard an odd scratching of the aluminum while pushing the barrel into the upper. I had to utilize a rubber mallet on the FSB to get the barrel seated all the way in.

What concerns me is the aluminum scratching sound and tightness when initally pushing the barrel into the receiver. I've done many barrel installations while an active duty armorer, but never encountered this before. I wondered if you folks would consider it ok on a new rifle.

I should add, it was no problem tightening the barrel nut after I had the barrel on the receiver.

As mentioned, the barrel did install and tighten/torque up wonderfully. I bought the lower and upper complete from RRA, all I had to do was install the barrel. The end result is a nice RRA 20 inch A4 with new FNMI Govt. Profile barrel. Pretty nice set-up, but I guess I need some reassurance regarding the above issue.

Thanks for the help!!

Sounds like a good installation to me. I wouldn't sweat it.

Thanks. I'm sure it'll shoot well....can't wait to try it.

I've heard that sound before, nothing to worry about.  It is the barrel extension stud fiting itself into the slot under torque.  There are usually slight variations in the slot width on the upper and/or barrel extension stud diameter between manufacturers, very slight.  They'll usually always fit, but some will be tighter, some looser.  When you hear that sound, assuming it isn't REALLY bad, it means you have a nice, tight barrel to upper interface.

I had a barrel one time that had a slight burr on the barrel extension that I didn't notice, it caused a similar sound (and a slight scratch, not deep enough to go into the aluminum).  Once it was assembled, it shot fine.

I had the tightness without the noise on a Bushy barrel to RRA A2 upper install.

Shoots like a house afire.

Danny

P.S. I'm half deaf too.

Why did you hit the sight base with the mallet instead of the muzzle? Even if there was no muzzle attachment on, the rubber mallet wouldn't hurt the crown.

Quoted: I had a barrel one time that had a slight burr on the barrel extension that I didn't notice, it caused a similar sound (and a slight scratch, not deep enough to go into the aluminum).  Once it was assembled, it shot fine.

+1 -- with the exception that my burr gouged through to the aluminum. :-(

Quoted: Sounds like a good installation to me. I wouldn't sweat it.

+1

Quoted: You read too many books and you worry too much.

Well, better worried now than sorry later.

Sounds like a nice, tight build.  My C7 Rifle build was a tight fit, too....and she shoots like GANGBUSTERS!!!!

Well, I would have to say I had a burr on the extension. I did find a few black specks of aluminum on one of the feedramps after I looked just now. I don't think it'll hurt anything though. It installed to good to mess with at this point. I'm sure it didn't casue that bad of a scrape.

Thanks for all the help.