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A pretty smart AR guy once told me that "a malfunction that can't be intentionally induced can't happen".
I would understand this to mean that we should be able to take an otherwise reliable carbine, install bad parts in it, and in this case get it to consistently object to completing the cycle of operation by giving us a bolt over base malfunction. That being said, I've never seen anyone who could intentionally induce the malfunction.
Its been my experience that weapons that consistently exhibit bolt over base malfunctions are a result of unserviceable magazines, rifle barrel extensions in carbine upper receivers or an out of spec lower receiver. Every now and them the stars align and a BOB malfunction will occur. We all now the drill from there... take cover and perform a remedial action drill and get back in the fight.
Well, if the gent and his son return next week, I'll throw their PSA upper on my DD lower and see if it runs. That'll rule out an out of spec lower if I still have malfunctions and either prove or dis-prove the bolt-outrun issue.
I did manage to get it to fire three rounds in a row, though, so if it's an out of spec lower issue, the stars must have somehow aligned with the angle of the magazine, etc.
Semper Paratus Certified AR15 Armorer
Personally, it sounds under or severely over gassed. I have had overrides. It came from running dirty and really hard, short stroking.
The reason I asked earlier about brass is because where that first brass lands before jamming up could lead to your culprit. Under-gassed with too much bcg weight or too heavy buffer, or too weak spring (short stroking). Or over gassed, too light buffer, or wrong spring. Most guns can be tuned properly by changing out components to create a balance.
IMO, Ejection angle is totally relevant.
That in combination with a lockback test, helps narrow down an over gassed/under gassed condition.
If the gas port turns out to be rifle sized, a CustomTune Gas Port can bring it back down to the .060" that it should be.
Black River Tactical
BRT OPTIMUM HFCL Barrels - Hammer Forged Chrome Lined 11.5", 12.5", 14.5"
BRT OPTIMUM Barrels - 16" MPR, 14.5" MPC, 12.5" MRC, 11.5" CQB, 9" PDW
BRT EZTUNE Preset Gas Tubes - CAR and MID
BRT Covert Comps 7.62, 5.56, 6X, 9mm
BRT MarkBlue Gas Tubes - BRT EXT, EXC and PDW Lengths
BRT MicroPin Gas Blocks - .750" & .625"
BRT MicroTUNE Adjustable Gas Blocks
BRT CustomTUNE Gas Ports
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