New Armalite AR-10 - Bolt doesnt lockback?

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11 years 10 months ago #16397 by j1mmyr1chter
New to AR-10s. Just bought one and discovered that the bolt does not slide back far enough to lock back. Factory stock has been replaced by seller with retractable carbine stock. My limited knowledge, but diligent Armalite research leads me to believe that the correct buffer tube, buffer, and spring are present, but I could be wrong. Anybody seen this? What am I missing? I haven't fired the rifle yet, and don't plan to until I get this action issue sorted out. Thanks for any guidance!

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11 years 10 months ago - 11 years 10 months ago #16398 by Turbo V6 Camaro
I have limited experance with my new ar-10 (haven't fired, to dang cold) but it is MUCH harder to lock back then the M-16 i fired in the AF. also when you release it, it is much more violent i did a :censored: the first time i ran threw the safety checks :woohoo:

good way to cut off a figure you dont anymore lol
Last edit: 11 years 10 months ago by Turbo V6 Camaro.
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11 years 10 months ago #16401 by j1mmyr1chter
Thanks Turbo, but I have really been after this and its pretty clear that something is keeping that bolt from going back far enough. Its like the buffers too long or something, but it matches exactly the specs on the Armalite sight, so I just dont get it. Buffers 3 and 1/4" and and about 5 and 5/8 oz.

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11 years 10 months ago #16402 by VTIT
A quick check would be to open it up, pull out the buffer and spring and see if the bolt carrier will physically fit in the buffer tube. If not you have a problem. If it does maybe the buffer or spring is stopping it from going back far enough.
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11 years 10 months ago #16404 by j1mmyr1chter
Done that. The buffer tube seems to be fine diameter-wise. There is definitely something keeping the bolt from going all the way back though. I just cant figure it out because the buffer seems to be right on the money size-wise, and the spring is within an inch of what Armalite says the measurement of the spring should be. Its strange, and I feel like I must be missing something simple, but I simply cant find it.

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11 years 10 months ago #16405 by VTIT
Check the length of the buffer tube itself. You say it was replaced maybe it is too short. Just throwing that out there. I am at work now or I could measure a stock one and let you know how long. Maybe someone else can answer it.

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11 years 10 months ago #16408 by LebbenB

VTIT wrote: Check the length of the buffer tube itself. You say it was replaced maybe it is too short. Just throwing that out there. I am at work now or I could measure a stock one and let you know how long. Maybe someone else can answer it.

This. How far away is the BCG from being able to engage the bolt catch?

Also, there's a chance the receiver extension was screwed too deeply into the receiver. It should be screwed in just enough to prevent the buffer detent from springing loose.

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11 years 10 months ago #16409 by j1mmyr1chter
Excellent LebbenB. I was thinking the same thing, it actually was in there just enough to hold that detent down (so I guess it was installed correctly), but I actually tried unscrewing another turn or so and then trying and no better. I will turn it back in to the correct position tonight ;-).

VTIT, I am on your page for sure. I am thinking that my tube may be about 1/2" or so too short (let the 'story of my life' jokes begin hehe). Anybody got a some specific measurements / measuring points?

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11 years 10 months ago #16410 by j1mmyr1chter
Oh and LebbenB, it looks like I am short by about 1/2 - 5/8" from the bolt catching.

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11 years 10 months ago - 11 years 10 months ago #16411 by LebbenB
OAL for an AR10 Carbine receiver extension is 7 5/8ths inches.

OAL for an M4 receiver extension is 6 15/16"
Last edit: 11 years 10 months ago by LebbenB.
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