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Posted: 10/12/2011 4:45:04 PM EDT
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My 6.5 Grendel Alexander Arms barrel/bolt combo build has been stove-piping. I believe the problem is related to an out of spec extractor due to the fact that the round will stay on the bolt even when turned towards the ground. Do any experts have advice?
The ejection pattern is at about one o'clock with the occasional case falling just outside of the rifle. The bolt does indeed lock back on an empty magazine. I am running an18" barrel with a standard A2 buffer/stock. Below is a picture of why I believe the extractor is out of spec: 
Below are two pictures of the extractor, it does not appear to have any burrs, and no brass shavings have been noticed. 
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Not really out of spec....but we've found that some of them are a bit sharp, and need to be gently polished with a dremel or jewelers file.
I originally had it happen with my 5.56 when I replaced the extractor, but 1 of my Grendels also had the issue. I used a flexible, fine sanding disc on the dremel and it worked great. Just be gentle, all you are trying to do is knock the sharp edge off. |
| I had that problem with two out of three Grendel extractors. I used a small piece of crocus cloth backed up by a thin stick and polished the inner face of the extractor groove, the face that pulls on the cartridge rim, then took the extractor and hit the portion that snaps over the rim on a power buffer using an 8" hard felt buffing wheel and some green chromium buffing compound to get a mirror finish. The gripping edge is now slightly rounded with a high polish and extracts and releases the case easily. |
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I polished the edges of the extractor and re-blued it up. After that it did not hold on to the cases as much as it did before. It would also fall free from the bolt face when inverted.
However, when I would slowly pull on the charging handle with a round in the chamber, it still would not let go when the point of the round passed the ejection port. I fixed this problem with the Alexander Arms bolt by purchasing an ejector repair kit from Midway USA which included an ejector, chrome spring, and a roll pin. When replacing the Alexander Arms ejector I measured it with calipers and the replacement was .0005 longer from the ejector recess to the top (not a big difference). The roll pin was longer and fatter in the repair kit. My 1/16" punch had a very tight fit in the A.A. bolt meaning that Alexander Arms uses a smaller roll pin. The spring was slightly longer in the repair kit and had more pressure. After replacing the ejector and ejector spring, the bolt finally threw the round. This was a new Alexander Arms bolt with ejection problems from the first shot. The ejector spring in the factory bolt was too weak and or cut too short, the extractor had a large grove with sharp edges which had the tendency to grab and hold on to the case rim. I know that some people cut their springs so the brass does not fly as far to ease recovery of their brass but I would rather have my rifle reliably eject the brass. The next problem to solve is the feed ramps. They seem as if they were designed for the 5.56mm. When the round is stripped from the magazine, the shoulder of the cartridge hits the sharp skinny groves producing two dents in the shoulder of the case. This is of course "ironed out" after the round is discharged but still leaves nice scratches in the brass and sometimes on the bullet itself (very minor). |
The dents that are being left in the shoulder can be seen below. This was 120 Grain Wolf MPT, the dents are not as noticeable in Lapua brass with hand loads which leads me to believe that Wolf uses a softer brass. The scratches in the brass are evident in all cases after firing. This may lead to inconsistent chamber pressures.
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Dented shoulders could be from bolt lugs riding over top round in mag.
1 o'clock ejection "with the occasional case falling just outside of the rifle" sounds like a potential overgassed system, especially if your 18" barrel has midlength gas. An overgassed system can cause seemingly unrelated issues, such as ejection problems, dented shoulders, erratic accuracy, etc. You can spend time chasing each individual issue and treating the symptoms, but until your gas system is right, it will be a frustrating experience. If the gas port is 0.090"+ on an 18" midlength 6.5 G, I strongly recommend an adjustable gas block. If the gas port is ~0.082" or less, a standard gas block should be okay. |
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Quoted:
Dented shoulders could be from bolt lugs riding over top round in mag. 1 o'clock ejection "with the occasional case falling just outside of the rifle" sounds like a potential overgassed system, especially if your 18" barrel has midlength gas. An overgassed system can cause seemingly unrelated issues, such as ejection problems, dented shoulders, erratic accuracy, etc. You can spend time chasing each individual issue and treating the symptoms, but until your gas system is right, it will be a frustrating experience. If the gas port is 0.090"+ on an 18" midlength 6.5 G, I strongly recommend an adjustable gas block. If the gas port is ~0.082" or less, a standard gas block should be okay. The gas system is fine, it was throwing the cases forward due to the fact that the rounds were staying on the bolt. That problem has been solved, but I think the C Products magazines are the issue with shoulder denting. The bolt does not ride over the round as it does fully chamber. I have tried my upper on 3 lower receivers and the problem exists will all. |
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