I did a search here and couldn't find quite the answer I was looking for. Maybe I missed it.
I just finished assembling my new upper using the following parts:
Sabre Defence 1:7 14.5in 5.56 chrome lined mid-length barrel
Rock River Arms BCG
Yankee Hill Machine ("Keyhole" marked) stripped upper
Clymer 5.56 GO and NO-GO gauges from Brownell's.
I assembled everything using the proper tools and a Snap-on torque wrench that was recently re-certified. Torqued the barrel nut to 35ft-lbs then tightened it until the next hole aligned with the gas tube.
I thoroughly cleaned the chamber of the new barrel and inserted the NO-GO gauge. It didn't even come close to closing. Good. I moved onto the GO gauge. The bolt began to slightly rotate into the locked position behind the locking lugs of the barrel extension. However, it would not go into full battery. I had another brand new RRA BCM laying around so I tried it. Same exact problem. I then tried chambering some M193 and various .223 Hornady and Prvi rounds. They all chambered with no more effort required than closing the bolt on an empty chamber. Next I tried a slightly used (less than 100rds) RRA BCG that I had out of another fairly new rifle. This bolt closed on the GO guage with only moderate force. (i.e. I was able to push it closed wit the palm of my hand.)
It's important to note that the bolts were NOT stripped during these test. Is that my problem? Will stripping the bolt give me the required added clearance?
Is there a known issue between RRA bolts and Sabre barrels?
Being that the bolt "almost" locks, would it be safe to shoot low powered .223 ammo to "break in" the new bolt and chamber?
Thanks for the help guys. This is my first time assembling an upper. I'm an anal retentive Mechanical Engineer so I like mechanical things to work perfectly!


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