AR-10 Question/Help

[young dunner]

I built (assembled) a .308 for a buddy of mine. The rifle set in his safe for 8-10 months before deciding to take it to the range. I went with him so we could run it and site in the optics that he bought for it. So, first issue is that it continually would not eject the spent case and the following round would jam in the middle of the ejection port. This happened numerous times and we decided to call it a day. I was thinking that since it had set so long unfired that it probably just needed a deep cleaning and lube.

I broke the rifle completely down. Tore down the BCG and cleaned it with a soft wire wheel on a Dremel tool. oiled everything up extremely well then checked the gas system. The gas system is correct for the rifle and aligned properly. Head back to the range a few days later and it now charges better and ejects the spent case flawlessly but does not chamber the next round. Its as if the gun is cycling too quickly.

Has anyone dealt with an issue like this? I'm thinking that maybe the springs in the Magpul mags are not stiff enough to push the next round up in time, maybe the buffer is not correctly weighted? Any ideas?

[AgBass01]

Sounds like a mag issue to me as well.

[sir shovelhands]

It sounds like it's short-stroking.

Have you single loaded it? If so, does it lock back when the mag is empty?

What mags are you using, what buffer, what buffer spring, gas length, barrel length, ammunition specs?

[SC-Texas]

What magazine are you using?

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[SC-Texas]

1. If you chamber one round on a empty magazine does the bolt lock back?

2. When you say it does not chamber the next round after ejecting, what is the failure? Is the bolt closing on an empty chamber?

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[StickSlinger]

check the buffer spring you might need to shorten it a little I had the same issue after I put a collapsible stock on mine after I shortened the spring it works just fine

[young dunner]

It sounds like it's short-stroking.

Have you single loaded it? If so, does it lock back when the mag is empty?

What mags are you using, what buffer, what buffer spring, gas length, barrel length, ammunition specs?

I have not tried this but will this weekend. Great advice, haven't thought of that. I will reply later with all of that other info but the mags are 10 round Magpuls.

What magazine are you using?

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10 round Magpul

1. If you chamber one round on a empty magazine does the bolt lock back?

2. When you say it does not chamber the next round after ejecting, what is the failure? Is the bolt closing on an empty chamber?

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I have not tried single loading but will this weekend. Yes, the failure is the bolt closing on an empty chamber.

check the buffer spring you might need to shorten it a little I had the same issue after I put a collapsible stock on mine after I shortened the spring it works just fine

I will give this a try after giving the other suggestions a shot.

Thanks everyone for the suggestions and advice

[SC-Texas]

Measure the receiver extension. How Long is it?

Do you know which receiver extension aka. Buffer tube you used? Make and model?

How long is the spring. What spring is it?

How long is the buffer?

How much does the buffer weigh?


What is the Make and model of the buffer and sping?

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[young dunner]

Measure the receiver extension. How Long is it?
7"

Do you know which receiver extension aka. Buffer tube you used? Make and model? Unsure.
Think it's just a generic from PSA, can't remember.

How long is the spring. What spring is it?
I believe the spring and buffer are from PSA. It's 11"

How long is the buffer?
2.5"

How much does the buffer weigh?
3.88oz, 110 grams

What is the Make and model of the buffer and spring?
PSA I believe

[young dunner]

Just got back from the range. With a single round chanbered and an empty magazine the rifle would fire and eject but return to the charged position. Also, on several shots it would not fully eject the spent case. I can manually cycle a full magazine with no issues. I'm now leaning toward the gas system or ammo.

[SC-Texas]

Just got back from the range. With a single round chanbered and an empty magazine the rifle would fire and eject but return to the charged position.

It is under gassed.

What gas block are you using?



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[SC-Texas]

Also check to make sure the gas key is tight on the bolt carrier

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[SC-Texas]

Also check the gas rings on the back of the bolt

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[young dunner]

It is under gassed.

What gas block are you using?



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It's just a generic .750 low profile billet gas block with 3 set screw under it

[spro]

Not sure if your issues are similar to mine. My AR-10 would jam constantly even after trying multiple mags. Changed from soft point to polymer tips and problem solved.