AR10 failure to feed.

[asquared19]

hoping someone may have some insight. I have an AR10 in 6.5 that I got to take out for the first time over the weekend. shooting was done with factory loads (hornady 140gr BTHP). I got situated pulled back on the charging handle and got ready to let the first load fly. Squeeze "click." I waited a sec to make sure it wasn't a hang fire. Pulled back on the charging handle and no round was loaded. Cycled the CH again and this time it stripped a load. got a solid bang this time. spent case was ejected. another squeeze "click." I tried to manually load another round and this time it wouldn't strip another round. long story short, out of all my attempts, only about 20% of the time did it properly load a round, either automatically via recoil, or manually be me operating the charging handle. to finish sighting in, I had to manually pull the CH, lock it back, load the next load in the chamber, then release the BCG. Extremely frustrating, but I still wanted to get sighted in. Any thoughts on this? if it only happened via auto loading, I would suspect under gassed, but with it happening on the manual operation I feel it's something different. BCG is an Aero Precision nickel boron. mags were magpul.

 

[chutem]

Sounds like mag to me, given the manual operation. Try a steel mag and ensure fully seated. Keep us posted on what you come up with.

 

[HandgunHTR]

1. Insert the mag with the BCG locked to the rear.
2. When you insert the mag, slam it up in there.
3. If that doesn't solve the problem, try a different mag
4. If a different mag doesn't work, check your mag catch/release. Make sure it is tight.

 

[dfrosch]

Load one in the chamber and insert an empty mag. Push the lower part of the bolt catch in and pull the trigger. If the BCG locks back, it's not undergassed.

 

[asquared19]

Load one in the chamber and insert an empty mag. Push the lower part of the bolt catch in and pull the trigger. If the BCG locks back, it's not undergassed.

This was the one test I wish I would've done while at the range yesterday. would be very telling.

 

[miningshawn]

It is the magazine. Switch to a steel magazine and enjoy life.

 

[Pres100]

not saying that this is your issue, but something to consider.... it may not be compatible?

from the Magpie website:

Optimized for use with SAAMI-spec 7.62x51/.308 Winchester ammunition

*NOTE: Compatible with older model Bushmaster .308 ORC, Remington R-25, and DPMS LR308 rifles, but not optimized for bolt lock functionality with newer models based on the DPMS GII design. NOT compatible with Armalite AR-10B, Springfield Armory M1A, Rock River Arms LAR8, FN SCAR 17S, PTR-91, HK417 or any other rifles that utilize M14, FN FAL, or HK 91/G3 patterned magazines.

 

[jonbearman]

Sometimes my ar-10 is the same but I usually have to seat it with some authority because it may be in enough to sort of cycle but you can usually seat it till you hear it snap in tight.If you put it in and try to just pull it out with out using the mag release and it comes out it wasnt seated. Hope this helps.

 

[ben lurkin]

Tough to diagnose but could be as simple as the gas block isn’t aligned with the barrel’s gas port. If that checks out then it may be as simple as cutting off a coil or two from your existing buffer spring. Proceed with caution by eliminating the mag issues as outlined above first though.

 

[Pawnee Bill]

Sounds to me like your AR10 is short stroking. Not getting enough gas to cycle the BCG all the way back.

 

[asquared19]

Sounds to me like your AR10 is short stroking. Not getting enough gas to cycle the BCG all the way back.

I thought that after the first shot, but then realized it happened when manually cycling the BCG via the charging handle. I am going to take a close look tonight and will see if my neighbor has a steel mag for me to try as well. Thanks for the input.

 

[HandgunHTR]

Sounds to me like your AR10 is short stroking. Not getting enough gas to cycle the BCG all the way back.

If that were the case, he would be able to chamber a round manually, which he stated he was also having issues with.
It is a mag issue. Either not seated correctly or the feed lips on the mag are off.

 

[LRPV]

My little cousin showed up with an AR10 he put together that wouldn't cycle right. It had the wrong buffer in it. AR15 buffer is longer than AR10 if I recall. It wouldn't let the bolt come back far enough.

 

[asquared19]

My little cousin showed up with an AR10 he put together that wouldn't cycle right. It had the wrong buffer in it. AR15 buffer is longer than AR10 if I recall. It wouldn't let the bolt come back far enough.

This is the buffer tube kit used. https://www.tacticalworks.com/Magpul-PRS-Completion-Kit-AR10-.308-PRS308.html

I have the PRSGen3 stock.

 

[Gargoyle]

Armorer's rule #1 for troubleshooting. Start with the magazine. Find a magazine that always works and wrap it in blue tape as a trouble shooting tool.

 

[Twdmar]

Make a few dummy rounds and put the rifle in a vise. Point a camera at the ejection port and record it while you try a couple mags.
You never said what kind of upper and lower it is, the ar10 is much less compatible across makers than the ar15.

 

[DiffEQ]

If it's short stroking and doesn't always lock back, you can do a few things to tune your cycling:

• *FIRST* make sure your gas port and block are lined up properly and properly anchored. Do you see leaking around the gas block?
• If your BCG is brand new, some are pretty tight as far as the bolt inside the carrier, and give a lot of resistance to pull out/ release of the bolt. Take it out, oil it up and do it by hand a few hundred times.
• Use a spacer washer on the buffer tube between the lower and buffer tube shoulder to move it back a 1/2 turn or so;
• file a little off the delrin nose on the buffer weight;
• If it still short cycles, but you've ensured it can lock back properly, even take a disc out of the buffer to reduce the weight to assist in the gun dynamics.

AR10 - a lesson that Mopar parts don't always work in Fords.

 

[Gargoyle]

Also helps to source as many parts possible from the same maker. I use Aero Precision and Ballistic Advantage. (BA is barrel maker for Aero, and usually a bit cheaper than Aero) Aero bolts and BA barrels match headspace great.

 

[asquared19]

Make a few dummy rounds and put the rifle in a vise. Point a camera at the ejection port and record it while you try a couple mags.
You never said what kind of upper and lower it is, the ar10 is much less compatible across makers than the ar15.

exactly what we are planning on doing later tonight.

 

[acloco]

Have you lightly lubed the buffer and spring?

If you can pull the charging handle back and pick up a round, buffer is not too long.


This can be a gas issue as well, not enough.....or...believe it or not....too much gas (things happening too quickly).


BEST item to do, video tape in slow motion from the initial trigger pull, thru initial extraction/bolt movement, through the entire cycle. You will see what is or is not occurring.