New AR 10T short cycles and fails to load next rou

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11 years 9 months ago #34137 by 1911POPO
New AR 10T short cycles and fails to load next rou was created by 1911POPO
I have a new AR 10T with approx 175 rounds that is short cycling and fails to load the next round. I have tried various ArmaLite magazines and a 5.4 oz buffer and a 10 oz Slash buffer.

Ejection of a fired case is normal.

The chamber and feed ramp required polishing which did not help any.

Any ideas? :banghead:

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11 years 9 months ago #34139 by jtallen83
Replied by jtallen83 on topic New AR 10T short cycles and fails to load next rou
I'm not a tech guy but I know they will want some more info like what type of ammo? What modifications have you made? What type of lube?
I would call Armalite myself, they have top notch customer service.
I'll be watching the thread so I can learn along, best of luck :usa:

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11 years 9 months ago #34141 by Siscowet
Replied by Siscowet on topic New AR 10T short cycles and fails to load next rou
JT is right, first question is ammo, second question is Armalite's Customer service number.
You have played with the buffers so that may be an issue in itself. I assume it did it with the OEM buffers. Barrel Length? Rifle or Carbine? Could be a gas block issue if the other reasons are ruled out. Armalite CS is the best call. Keep us informed, we are always looking to learn.

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11 years 9 months ago #34156 by OleCowboy
Replied by OleCowboy on topic New AR 10T short cycles and fails to load next rou
All of the above +

1) Are there any modifications to buffer, mags, feed ramps, BCG etc etc, either by your or someone else?

2) Is gun NEW as in NIB or used, if used we all know the previous owner only fired < 25rds in spite of the fact the peep hole on the sight is actually worn out...

3) At any time in your firing has the weapon ever functioned properly? Does it do this 100% of the time, if not what % of the time does it do it, your best guess estimate

4) Ammo: New, reload, make, model, age, clean?

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11 years 9 months ago #34159 by Siscowet
Replied by Siscowet on topic New AR 10T short cycles and fails to load next rou
Check your gas key, is it staked properly? also make sure your gas rings in the bolt carrier group are intact and giving a good seal.

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11 years 9 months ago #34161 by 1911POPO
Replied by 1911POPO on topic New AR 10T short cycles and fails to load next rou
I'll try to answer all the questions.

The AR 10T rifle with a 20 inch barrel was new in the box when I bought it at the gun shop where I work a part time retirement job. No one else has touched the gun except for me, a retired mechanical engineer with 45 years of shooting, reloading and firearm building experience, and our gunsmith who has 40 plus years experience. We both are certified armorers on the AR 15 platform by several companies whose products we sell.

The rifle ran fairly well when new but started short cycling just after barrel break in. The feed ramps were marking the brass and the chamber was leaving reamer marks on the brass. The rough finish in the chamber and the feed ramps was verified by inspection with a bore scope. Both areas were polished to correct the noted defects.

The rifle currently has had approx 175 rounds fired thru it.

The standard Armalite buffer was replaced by a Slash 10 oz buffer, no improvement was noted. The Slash 10 oz buffer was taken out and the original 5.4 oz buffer was installed.

I have 7 brand new Armalite manufactured magazines which have all been test fired in the rifle. No difference or improvement has been noted.

The BCG will lock back with manual operation with a magazine installed. The BCG will not lock back on an empty magazine when the gun is fired.

The rifle has been tested with new factory fresh 150 grain and 168 grain ammo from Federal, Winchester, Remington and Hornady. The military rounds used are various years of manufacture of Lake City Arsenal, as well as match grade hand loads, using Lapua brass fire formed to the rifle chamber and Sierra 135 grain MK, 150 grain MK 168 grain MK bullets.

The individual component parts from my rifle have been inspected and compared with new Armalite components from 2 new on the shelf firearms. The only differences noted, was the gas block is sitting hard against the gas block shoulder of the barrel and there are no shims or spacers between the gas block and the barrel shoulder.

The gas system has not yet been torn down for inspection.

I hope this is enough information to help but if not just ask.

Thanks,
Dave

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11 years 9 months ago #34162 by 1911POPO
Replied by 1911POPO on topic New AR 10T short cycles and fails to load next rou
Gas ring looks just like a new one and passes all gas ring test.

The gas key is torqued and staked.

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11 years 9 months ago #34167 by OleCowboy
Replied by OleCowboy on topic New AR 10T short cycles and fails to load next rou
What you have done or so it seems at this time is to eliminate most of the common causes. That is the good news and the bad news.

There are 7 parts of the AR gas system. In the upper receiver group, you have the barrel (gas port), front sight base, and gas tube. In the bolt carrier group you have the gas key, the carrier, the bolt, and the gas rings.

Have you checked from the gas tube back to the gas port?

Do you ever have and issue with the BCG not staying back??? A problem I had with my brand new AR10T...

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11 years 9 months ago #34171 by Siscowet
Replied by Siscowet on topic New AR 10T short cycles and fails to load next rou
1911 I would say you have done due diligence. Indeed it is time to have Armalite make it right. With a lifetime warranty that shouldn't be an issue. Good luck. I can"t think of anything else. I am betting it is related to the gas block discrepancies you noticed. Just a guess.

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11 years 9 months ago #34172 by jtallen83
Replied by jtallen83 on topic New AR 10T short cycles and fails to load next rou
:I-agree: There doesn't seem to be much left beside the gas block or something really freakish in the gas tube, the tube could be a hair short and cause this?????
It sucks to have issues with a new rifle but Armalite will square it away for sure. :usa:

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