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Old 07-16-2012, 10:43   #1
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FTF, eject, etc

Hello all,

I have a friend who came to our range yesterday to sight in his new to him AR. Oddball AR at least 15 years old. Research showed Ruger cast the lower according to him but no marks on barrel at all, receiver is marked "223/5.56".

Rifle was just cleaned ---- I took it apart to make sure they assembled properly and it was. We were shooting Wolf 55 grain and their mags were an off brand. We tried rounds of wolf, Federal SS109, and some hot SMK 70 grain handloads in their mags, in a known good steel magazine of mine, and out of one of my magpul mags that NEVER jam in either my Stag or my PSA.

Still more often than not spent cartridge would eject but fresh round wouldn't chamber even though bolt did cycle and lock. Almost like it didn't get blown back quite enough.

I know the guy they bought it from and also know it was a safe queen for at least ten years.

Since we've gone through mags and ammo anyone have any suggestions as to what to check next? Recoil buffer and spring?

Any help appreciated because to the eye everything looks good.

Many Thanks,

Art
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Old 07-16-2012, 13:55   #2
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Sounds like the gas tube or gas block isn't sealed quite well enough, creating lower gas pressures. Or, it could be that the gas port is plugged with 10+ years of gunk from the safe, thus creating the lower pressure.

Before you go tearing it all apart, I would suggest checking putting it on another lower that works, so you can rule out the buffer/spring combo. Once you eliminate this, then you can check on the gas system.

TG
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Old 07-16-2012, 16:28   #3
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+1 on trying a different lower.

Could be running a rifle buffer in a carbine tube in this unknown "oddball". If it still jams on a reliable lower then TG is right, something with the gas system. You did check to make sure the bolt was installed in the BCG the correctly?
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Old 07-17-2012, 04:17   #4
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Great ideas ---- try a known good LOWER or a known good UPPER? Shoot maybe I'll try both and see what happens.

Yes, bolt IS installed in BCG properly, that was first thing I checked. That and assembly of bolt itself are all good.

Thank you!

Art
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Old 07-17-2012, 13:35   #5
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Originally Posted by Tazman1602 View Post
Great ideas ---- try a known good LOWER or a known good UPPER?
Try both... Then you'll know for sure which "half" of the gun is giving you fits. Be easier to diagnose then.
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Old 07-18-2012, 06:23   #6
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If I were trouble shooting this I would try another lower to at least tell me what is the problem, which would eliminate alot of trouble shooting. No reason to trouble shoot the lower if it's fine. Also try this lower on one of your uppers while you are at it.

MY first thought is rifle spring in carbine tube. Or could be an after market competition spring with too much tension. 2nd thing I'd check is gas block and gas tube to ensure proper alignment and no blockages. But all this has been said, I'm late to the party
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Old 07-18-2012, 07:38   #7
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Thanks for all the input guys!

Art
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