Problems with new AR10 build cycling.. OPINIONS NEEDED!

[m8112]

I had the same problem with a Aero P upper/ lower build AR10. Changed out the charging handle to a different handle solved the problem. Very little difference in the feel between the handles. It did the trick. 300 hundred rounds later not a single problem.

 

[nwslopoke]

It's a "milspec" ar10 LPK and ar10 buffer tube kit. What was said above about the hard primers and primer depth is very valid but seems to be more prominent in the 7.62x39 builds. I'm anxious to break down the lower, check out the springs such, and get back out with some higher quality ammo. If it's fixed, I will personally buy each one of you a

Edit: @nwslopoke what ever ended up fixing your problem?

Going back to a "milspec" trigger. In my case PSA's EPT nickel boron. In my AR10 I have a LaRue MBT 2 stage trigger and it's been reliable even with steel case, which I rarely use. Mainly due to when I was stocking up on 308 ammo the price difference wasn't that much.

 

[Defense Minister]

One more thing to check is that the gas tube is aligned properly and entering the upper receiver straight, otherwise it could be getting stuck in the key.

 

[Jv22]

One more thing to check is that the gas tube is aligned properly and entering the upper receiver straight, otherwise it could be getting stuck in the key.

Thank you for your input. Just got home, I'm going to break it down and start checking right now

 

[Jv22]

I had the same problem with a Aero P upper/ lower build AR10. Changed out the charging handle to a different handle solved the problem. Very little difference in the feel between the handles. It did the trick. 300 hundred rounds later not a single problem.

This seems very interesting to me.. I'm going to have to look at my charging handle to make sure it's not interfering with the frame

 

[Jv22]

Okay guys. Heres what I found. According to the picture that was posted, my hammer spring is correct. The gas tube looks good and no evidence of catching or rubbing on either surface.

 

[Jv22]

One thing I do notice that is extremely stiff is the Ejector which makes sence why it was leaving round marks on all the heads.. any suggestions there? I'm about to let it soak in a very thin penetrating lube as previously mentioned.

 

[Jv22]

Here I show the pin protrusion

 

[Jv22]

I found this spot rubbing on the BCG.. cant seem to find any other strong indicators other than that ejector is very, very stuff. Let me know what you all think as I let the BCG soak. Thanks!

 

[Jv22]

Here is the opposite side of the same piece.. should I be seeing this kind of wear with only ~12 shots ? Never noticed anything like this on the other ARs .. maybe because it wasn't lubed well enough it got some metal on metal wear but Not sure!

 

[BrandonQuixote]

Marks on the primer are consistent with normal floating firing pin, not a good source of info on the failure. Is the trigger resetting after the cycle? Though it usually causes a run-away full auto not a failure to ignite- check your disconnector spring to make sure its WIDE SIDE DOWN in the trigger. They often go in narrow side down because its easier to seat as such. Check your hammer spring set and trigger spring as well, since youre there. In some cases its possible to cycle just enough to eject but not fully reset the trigger onto the sear and disconnector. Check your gas block alignment too.

I have a 13" 308 that i shoot the piss out of suppressed and very rarely lubricate beyond a slathering of grease on the BCG every 4-6 months. They're not as finicky as people say if you use quality parts and don't stack tolerances and they DEFINITELY don't need to be drowned in lube to run. I've never had problems with hard bubblegum commie primers (wolf) in my reloads that ive used in ANY gun. Sounds more like a spring issue, very unlikely but possible gas issue.

 

[BrandonQuixote]

I found this spot rubbing on the BCG.. cant seem to find any other strong indicators other than that ejector is very, very stuff. Let me know what you all think as I let the BCG soak. Thanks!

View attachment 1095265

that's normal for the cam pin. AR10's often have issues ejecting so you'll find double ejector o-rings and very stiff springs to ensure good extraction. That's normal.

 

[rabidmullet]

I've never run steel case ammo in my lr308 but your cases look rough to me(ejector smear(yellow) and a gouge left by the extractor(red). I would agree with some others that you probably aren't getting back into battery for the second shot for some reason. If you've never had a failure on your first shot, and the trigger is resetting before the second attempt, I think you can rule out light primer strike and trigger spring issues. If those were the case you would see the issue when manually charging too. Could be under gassed and short stroking, or maybe there is an issue with the bolt lockup. Here are some tests you can try to isolate the issue.

It's already been mentioned but the easiest way to see if you are under gassed is to check for last round hold open. Put a single round in the mag, fire it and make sure the bolt locks back. If it doesn't your under gassed. Your gas block might not be aligned, gas port might be undersized or something along those lines. If you are under gassed the bolt can move back far enough to eject the case, but doesn't have enough energy to get completely back into battery for the second shot.

The next thing I would check is that you can seat rounds in the bolt and that the bolt isn't out of spec or something. Take your bcg out and slip a case rim under the extractor. After that you should be able to push the case back against the ejector to fully seat the case against the bolt face.

Another test I would try is to take your upper off and your bcg out.. With the muzzle pointing at the ground put a round in the chamber. Put you bcg in but let it drop down on the round in the chamber. You are just using gravity to push the bcg into battery instead of how it is normally happens with the buffer spring. Gravity should be enough for the bolt to go into battery. If it doesn't than something is hanging up. The lugs could be out of spec or I'm wondering if your extractor might be stuck or too stiff and that might be causing gouge marked in red and trouble getting into battery. You also mentioned the extractor was really tight. After dropping the bcg and checking it goes all the way into battery pull it back up. You want to make sure the extractor is getting over the case rim. The round should come up with the bcg.

 

[Jv22]

that's normal for the cam pin. AR10's often have issues ejecting so you'll find double ejector o-rings and very stiff springs to ensure good extraction. That's normal.

Hey thanks @BrandonQuixote. I guess I have never noticed it marring the metal that much.. need to check on other builds. I have reached out to BCA after checking the trigger group assembly. Hammer spring and trigger spring are correct according to photos.

I've never run steel case ammo in my lr308 but your cases look rough to me(ejector smear(yellow) and a gouge left by the extractor(red). I would agree with some others that you probably aren't getting back into battery for the second shot for some reason. If you've never had a failure on your first shot, and the trigger is resetting before the second attempt, I think you can rule out light primer strike and trigger spring issues. If those were the case you would see the issue when manually charging too. Could be under gassed and short stroking, or maybe there is an issue with the bolt lockup. Here are some tests you can try to isolate the issue.

It's already been mentioned but the easiest way to see if you are under gassed is to check for last round hold open. Put a single round in the mag, fire it and make sure the bolt locks back. If it doesn't your under gassed. Your gas block might not be aligned, gas port might be undersized or something along those lines. If you are under gassed the bolt can move back far enough to eject the case, but doesn't have enough energy to get completely back into battery for the second shot.

The next thing I would check is that you can seat rounds in the bolt and that the bolt isn't out of spec or something. Take your bcg out and slip a case rim under the extractor. After that you should be able to push the case back against the ejector to fully seat the case against the bolt face.

Another test I would try is to take your upper off and your bcg out.. With the muzzle pointing at the ground put a round in the chamber. Put you bcg in but let it drop down on the round in the chamber. You are just using gravity to push the bcg into battery instead of how it is normally happens with the buffer spring. Gravity should be enough for the bolt to go into battery. If it doesn't than something is hanging up. The lugs could be out of spec or I'm wondering if your extractor might be stuck or too stiff and that might be causing gouge marked in red and trouble getting into battery. You also mentioned the extractor was really tight. After dropping the bcg and checking it goes all the way into battery pull it back up. You want to make sure the extractor is getting over the case rim. The round should come up with the bcg.

View attachment 1095359

Thank you very much for your thoughts @rabidmullet ! I need to get back out within the next couple days with better quality ammo.

 

[Husky]

I'm interested in what you find is the problem as i am having the same with .223. I got an upper kit and took it out the range and it would only fire one or two rounds and do the same. After oiling the moving parts well it seemed to improve it with one exception, The first round doses not fire just like yours, just makes a mark in the primer and then to get the bolt open i have to pull on it while tapping on it with a hammer. After that all rounds work with no problem. It does this every time with the first round only. I use reloads and factory. All loads are with brass cases. usually lake city.

 

[rabidmullet]

I'm interested in what you find is the problem as i am having the same with .223. I got an upper kit and took it out the range and it would only fire one or two rounds and do the same. After oiling the moving parts well it seemed to improve it with one exception, The first round doses not fire just like yours, just makes a mark in the primer and then to get the bolt open i have to pull on it while tapping on it with a hammer. After that all rounds work with no problem. It does this every time with the first round only. I use reloads and factory. All loads are with brass cases. usually lake city.

This is different. If you're having issues with the first round than it's not a gas issue. You shouldn't need to use a hammer to get your bolt open, especially if the round wasn't even fired. Since you mentioned you're using reloads I'd make sure the rounds chamber properly and you don't have a sizing issue. You should be able to easily push the round all the way into the chamber, turn the upper over and have he round fall back out. If rounds are chambering easily by hand I'd check the lockup between your bolt and barrel extension, but this sounds more like a stuck round/case preventing the bolt from fully closing and why you have to use a hammer to get it back open.

 

[Freshman]

Have you checked headspace? Short headspace would cause difficulties going into battery. If you are near the Beaverton/Aloha area, you are welcome to stop by my shop. We can check for and correct short headspace.

 

[mhayd93]

With the muzzle pointing at the ground put a round in the chamber. Put you bcg in but let it drop down on the round in the chamber. You are just using gravity to push the bcg into battery instead of how it is normally happens with the buffer spring. Gravity should be enough for the bolt to go into battery.

If you do this procedure, I would strongly recommend you do not use a live round! With a free floating firing pin and the bcg slamming down unimpeded on a live round, there is potential for a slam-fire.

Use either a snap-cap, dummy-round, or a spent case if you are going to try this.

 

[Jv22]

If you do this procedure, I would strongly recommend you do not use a live round! With a free floating firing pin and the bcg slamming down unimpeded on a live round, there is potential for a slam-fire.

Use either a snap-cap, dummy-round, or a spent case of you are going to try this.

Yes I realized this as I was reading it, but I appreciate your safety concern!! Good information for anyone else reading thank you

 

[rabidmullet]

If you do this procedure, I would strongly recommend you do not use a live round! With a free floating firing pin and the bcg slamming down unimpeded on a live round, there is potential for a slam-fire.

Use either a snap-cap, dummy-round, or a spent case if you are going to try this.

Always good to be as safe as possible but how is this any different than anytime an AR is charged or cycled in normal use? if anything it's a lot slower. You could also take the firing pin out when testing. The test is useful because the weight of the bcg should be just enough to get the ejector over the rim of the case and the bolt to lock up to confirm everything is moving freely.