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Posted: 5/16/2016 5:45:36 PM EDT
| Recently completed an economy "AR10" build using a PA10 lower and upper. But bolt, barrel, gas block/tube are all Anderson. When test firing, I had numerous failures of the bolt to go completely into battery - would stop just short and jamb. Lots of brass shavings on the bolt face. Also, when this happened, it took took considerable force to retract the bolt - had to give the charging handle a solid "wack." I suspected the extractor may be too tight. So I stripped down the bolt and found there were 2 o-rings on the extractor spring. Never seen this before. My question is, Is this normal on an AR10 or did I get a "Monday morning bolt assembly?" Email to Anderson has gone unanswered. Plan to remove 1 o-ring and retest. Your thoughts will be appreciated. |
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Give Anderson a call............I can't remember his name......but I believe I asked for the tech department, technical problems that sort of thing..........I had issues with some of their product and they promptly refunded my money.......they were very helpful and first class
What type of Ammo, factory?? Reloads??? etc Did you check headspace??? Did you clean chamber and bcg before using???? I used one of their 308 barrels and had good luck with it............... |
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Sounds like a rough chamber.
Break your rifle down, manually loaf a round into the chamber and loft the muzzle up. Round should fall out well before 90* angle. Should fall out with gravity only. If not, chamber needs to be reamed. Or possibly, but less likely, your barrel is out of spec, or bcg, or possibly upper. But if you're able to get a few rounds out, this is very unlikely as these issues usually result in failure to chamber at all. I bet is a rough chamber. It swells ever so slightly when heated, might be just enough to limit extraction. On the 2 o-rings, this is usually a bandaid. You shouldn't need both, only 1. Is possible the springs they use are weak, and the extra ring is needed for function. If that's the case, swap the spring with one from a more reputable source. Try the round with gravity first. If it passes that check, strip the bolt, clean it real good with brake cleaner, then lube it real good. Like anal virgin lubed up. For initial break in of the components, it's best to be dripping wet. |
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Thanks for the responses.
Maybe I should clarify that this was occurring about 3 to 4 times every 10 rds. Not every time. Rifle chamber/bore clean. Ammo was ZQ factory ball (MKE '15) and South African surplus ball '81. My son's DSA SA58 ate both without a hitch. Unfired rounds drop in/out of chamber easily. I still suspect too much tension on the extractor - causing it to fail to over ride the rim. I'll remove 1 o-ring and test fire again. Will let you know. |
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Chamber could still be tight. 3-4 rounds is enough to heat it up if it's tight. That will cause an issue. Then, while clearing the malfunction, rifle cools enough to go a few more rounds.
Try with one o-ring. If it still has issues, you'll need to have your chamber reamed with a good reamer. The problem is the reamers wear out kinda fast, especially in large production shops. They probably don't service their tools as often as they should, they wear out quicker, resulting in an undetermined amount of barrels getting by with bad chambers before they swap out the tooling. Then you gotta count on the guys further down the line to do proper QC checks. Anyways, shit happens. Post back with your results. |
Sorry for the long delay. Finally got out to the range today. Functions 100% with a single o-ring on the extractor spring. Wonder if it even needs that. Bolt still needs work - fired casings had a visible "punch" mark on the base. Ejector works but I think its bottoming out under compression. Maybe some junk in the hole or spring is too long. Seems this Anderson bolt has turned a project into a "project!" 
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