01-30-2023, 05:33 AM
If the bolt carrier can be cycled by hand with an empty mag and is caught by the bolt catch without a problem, then you need to look at other areas.. But first separate the upper from the lower and then insert the bolt carrier into the buffer tube until it stops in the buffer tube and measure the distance from the back of the carrier key to the receiver..There should be at least 2 quarters width clearance. Check video below.. The bolt carrier should be 6.667 to 6.677 in length minus the bolt..I'm assuming you already tested the gas rings..
I have seen only one buffer tube that I needed to replace that was out of spec. It wouldn't allow the bolt carrier to cycle far enough back and it would barely pass the bolt carrier catch at full cycle..If your bolt carrier is at proper length, I would try another bolt carrier to see if it behaves any different. Every lower will have different friction values such as the type of trigger, buffer tube quality, mag placement in the lower, etc. Did you do the recoil spring-buffer inspection? Here is a good video of these test..https://www.youtube.com/watch?v=kvfr4Xb3wLY&t=29s
Just do the process of elimination with your lower and you should be able to find the problem if your upper functioned fine with the gunsmiths lower..
If all things being equal and the lighter bolt carrier seems to fix the problem, then your rifle is already running on the edge of short stroking..Your rifle should run equally reliably with a standard weight bolt carrier..
I have seen only one buffer tube that I needed to replace that was out of spec. It wouldn't allow the bolt carrier to cycle far enough back and it would barely pass the bolt carrier catch at full cycle..If your bolt carrier is at proper length, I would try another bolt carrier to see if it behaves any different. Every lower will have different friction values such as the type of trigger, buffer tube quality, mag placement in the lower, etc. Did you do the recoil spring-buffer inspection? Here is a good video of these test..https://www.youtube.com/watch?v=kvfr4Xb3wLY&t=29s
Just do the process of elimination with your lower and you should be able to find the problem if your upper functioned fine with the gunsmiths lower..
If all things being equal and the lighter bolt carrier seems to fix the problem, then your rifle is already running on the edge of short stroking..Your rifle should run equally reliably with a standard weight bolt carrier..