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Old 03-10-2014, 9:50 AM
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Quote:
Originally Posted by Rusty Scabbard View Post
Buffer 'H' in the middle of your post looks chewed up by running into the buffer stop pin. What causes this ? How you do fix it ? If upper and barrel ext. are mated correctly and bolt carrier is within spec, I don't see how this can happen. But I have seen rifles with this problem.
Buffer detent related misfires:
Either the carrier is too short or the buffer detent hole is located too far to the rear.
When either of these conditions exist, the buffer comes to rest on the detent and the detent keeps the weights inside the buffer from hammering the carrier closed.
It is normal for the bolt carrier to bounce off of the barrel extension after impacting it.
In a proper configuration, the weights inside the buffer will be flying forward just after the carrier bounces rearward.
The moving weights hammer the carrier closed again before the hammer tries to strike the firing pin.
If the carrier is not fully closed, the firing pin will not get fully hit by the hammer.
If the buffer detent prevents that, you could have a carrier that is open by 0.030" or so that will catch more of the hammer energy instead of the firing pin/primer taking all the hammer's impact energy.
The hammer energy gets wasted into the carrier and the result is a misfire.

The test for this condition is to remove the buffer detent and see if the misfires go away.
If the misfires are eliminated by detent removal, you can simply leave it out or you can mill the detent hole oversized and sleeve it back down while relocating it forward.
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Last edited by ar15barrels; 03-10-2014 at 12:48 PM..
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