Long time reader, first time poster...great site, gentlemen.
I've done the search feature and have read around 10 threads dealing with similar issues.
What I have...and not completely Colt:
Colt upper w/ DD LW HF 16" barrel (carbine gas)
BCM guts (BCM BCG + CH)
Colt Lower (all factory + H2 buffer)
This build is new and a backup to an identical build. Upper was assembled by Specialized Armament. Factory springs in all components and well lubed with SLIP EWL.
The problem:
First range session, 100 rounds and no issues; sight in and function check. Second range session and one FTE spent casing at round 70; extractor tore the rim off. Popped out easily with cleaning rod. Did single round mag test to check pressure and got 10 consecutive solid lockbacks. Cleaned the weapon, cleaned chamber thoroughly and hand polished the chamber with a cotton chamber brush and a little Flitz to smooth out any roughness.
Back to range (third trip), made it through 140 rounds, FTE; extractor tore the rim off. Shooting was consistent with some rapid fire (doing some drills) and the upper was plenty hot.
Ammo used is Aguila 55 grain .223 and I've got a few thousand rounds of this on my identical build with no issues. Aguila tends to run on the hot side for .223.
I'm thinking the issue may be a tight chamber, but would like to know what some of experts here think before I contact Mr. Elmore and he yells at me for not using a Colt barrel and Colt BCG.
Thank you for the help, gentlemen.



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