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Posted: 8/11/2008 4:03:47 AM EDT
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On my build, there's a few things wrong I believe it may be caused by an excessively long upper, but maybe it's actually due to something else. 1. The buffer hits the buffer retaining pin. This is easily confirmed by the fact that it's chewed up all around the sides of the buffer with pin marks. it's not being caused by the carrier. When I look as I put it together, the carrier is slightly recessed (not flush) in the upper. 2. The ejection of cases takes place to the 1-2 o'clock. Cases dent against the rear side of the ejection port when they eject. 3. I get poor performance (~3 MOA) from a rifle that should be capable of better with match ammunition. I'm starting to think this may be related, but who really knows. I installed this build according to all instructions. Torque to spec with a torque wrench, etc etc. Any suggestions? |
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If the buffer retaining pin hole is drilled too far back in the reciever, the very outer edge is going to get hammered to hell. Only solution here is to get the lower receiver replaced. As for the cases being dented by the back of the ejection port, the face of the bolt should never retract behind the back of the port (should limit out about 1/4" in front of the back lip). In cases like this, could be that the receiver extension was not installed far enough into the receiver (some cheap tubes have to me shortened to index correctly anyway), or the receiver extension was milled too deep. As for dents in the middle of the case (brass off the deflector), this is normal. |
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Is the back face of the barrel extension even with, or just slightly proud of the inside of the upper receiver? Could be that the B/C is too short in your case, or the barrel is having problems up front. Really, if you bought a complete upper, then just get the manufacture on the phone to resolve the problem. Without having the rifle in hand, this could go 20 questions until we discover the true root of the problem. |
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The upper is a DPMS A3 (railed) model with a post-ban Bushmaster 24" NATO HBAR(1/9) barrel which I installed. The BC and Bolt are both Bushmaster as well. I'll check the barrel extension as soon as I get a chance. I realize that this is probably pretty vague; however I do appreciate the help. EDIT: The extension falls just short of being far enough into the receiver to match up with the beginning of the ejection port. |
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