Looking for an AR-15 expert, intermittent feed issue

[762x51]

i think it's the mags. i have the same issue with my 6.5 creedmoor with different factory loads. some manufacturers, i can load all 20 rounds and no issues. with hornady match ammo, the bolt won't cycle with a fully loaded mag. there's so much pressure on the bottom of the BCG that it can't ride all the back to pick up the next round.

you've verified everything else i can think of. gas tube alignment would have been my next guess. i had a buddy that built a 10.5" 5.56 pistol and it wouldnt cycle after 3-4 rounds. i took the gas block off and realigned it and he was mag dumping in no time.

 

[Winkfish]

I put the original buffer spring back in, set the gas block to 4.5 turns out. I then took a 10 round magazine with the lips turned out just a bit. Loaded it with 10 rounds of ammo and all the rounds fired without fail. The brass all landed in a little pile at the 5 o clock position.

The brass only had a minor ding on the case mouth so I thought all was working well. The bolt locks open after the last round as well.

I played around with a 15 round mag with modified lips and 10 rounds installed as well. They all fired without fail. I went through a total of 80 rounds and not a single failure. During the testing I also adjusted the gas setting a little as well and settled in on a position that put the brass in a pile at the 4 o-clock position.

The final 10 rounds at 100 yards went into .5" The wind was blowing around my little target so I am happy with that.

It looks like adjusting the lips on the magazine was the issue. I guess I should have asked the internet earlier rather than blowing through so much ammo trying to figure it out.

Thank you for all of you who provided feedback and assisted me in solving this issue.

 

[Orange Dust]

Glad that fixed it. Knew it almost worked and it wouldn't take much

 

[Stonyman88]

Good Morning, I am wondering if any of you AR-15 experts can help me out with an issue I am having.

Here are the Gun Spec:
6mm ARC, Factory ammo 108gr ELDM or handloads @ (108gr ELDX, BR4 primer, leverrevolution, at 2,732 fps)
Bartline 24" barrel 1:7 twist
Triggertec Diamond 2 stage trigger
Carbine length buffer with a standard 3 oz buffer
6.5 Grendal bolt Gen 2 verified with face depth measurement
Tried both standard spring and +15% power wolf spring
Superlative arms adjustable gas block. Rifle +2" gas system .092" gas port
CMMG and ASC metal magazine both 10 and 15 round

So here is what is going on.
Start with the gas block turned out about 4.5 turns per factory specs.
Place a round in the magazine. it fires and the bolt locks open. I clean the barrel and repeat. I work my way up to 3-5 shot groups and repeat. Everything cycles fine and the guns shoot well. Shoot 5 shot strings to 100 rounds. At this point I have not shot the gun with more than 5 rounds in the magazines.

Then I do load development on some ELDX and Leverrevolution powder. Shooting 3-5 shot groups it works just fine. This is across 6 different magazines all 10-15 rounders.

Now I am around 200 rounds down the tube.

This gun is setup for PRS and is going to be my daughters gun for this season. Now we are going to try and run a normal 10 shot stage. start shooting the gun. around shots 5-7 I will get a failure for the bolt to lockup up / go into battery. In some cases I am able to hit the forward assist and close it, then fire the gun. Other times the round is not far enough out of the magazine to allow that to happen. In some cases it is close to going into battery and when you pull the trigger it just goes click. If I drop the magazine, I am able to pull the charging handle, let it fly and it locks up. I am then able to pull the trigger and the round goes off.

If I single feed, no issues. if I put 3-5 rounds in a magazine no issue. This testing is being done on the factory ammo and not the reloads.

I have played with the gas system and dialed it in so that it is cycling fine and putting the brass at about the 4-5 O-clock position in a nice little pile.

I have tried different buffer springs to see if a stiffer spring would aid in lockup but it has not. I went to a different bolt carrier group and tried that on both springs and that didn't help either.

I am into this about 500 rounds now and I am unable to get it to run a full 10 rounds without a failure. This is starting to get a little expensive to figure out.

This problem will occur on reloads and factory ammo.

If anyone has any suggestions please let me know, I am at a loss and not sure what to do next.

Thank you,

Have you check the front of the mag. sometimes the neck of the brass will catch on the front of the mag and cause it to slow it down enough to cause a round from not going in to battery . Maybe even the back of the mag could be catching the bolt. Have you checked the shoulder before and after you fired a round, make sure the throat is cut correct to allow the bolt to close. Everyone here seems to be on the same page

 

[TXTrained]

Good Morning, I am wondering if any of you AR-15 experts can help me out with an issue I am having.

Here are the Gun Spec:
6mm ARC, Factory ammo 108gr ELDM or handloads @ (108gr ELDX, BR4 primer, leverrevolution, at 2,732 fps)
Bartline 24" barrel 1:7 twist
Triggertec Diamond 2 stage trigger
Carbine length buffer with a standard 3 oz buffer
6.5 Grendal bolt Gen 2 verified with face depth measurement
Tried both standard spring and +15% power wolf spring
Superlative arms adjustable gas block. Rifle +2" gas system .092" gas port
CMMG and ASC metal magazine both 10 and 15 round

So here is what is going on.
Start with the gas block turned out about 4.5 turns per factory specs.
Place a round in the magazine. it fires and the bolt locks open. I clean the barrel and repeat. I work my way up to 3-5 shot groups and repeat. Everything cycles fine and the guns shoot well. Shoot 5 shot strings to 100 rounds. At this point I have not shot the gun with more than 5 rounds in the magazines.

Then I do load development on some ELDX and Leverrevolution powder. Shooting 3-5 shot groups it works just fine. This is across 6 different magazines all 10-15 rounders.

Now I am around 200 rounds down the tube.

This gun is setup for PRS and is going to be my daughters gun for this season. Now we are going to try and run a normal 10 shot stage. start shooting the gun. around shots 5-7 I will get a failure for the bolt to lockup up / go into battery. In some cases I am able to hit the forward assist and close it, then fire the gun. Other times the round is not far enough out of the magazine to allow that to happen. In some cases it is close to going into battery and when you pull the trigger it just goes click. If I drop the magazine, I am able to pull the charging handle, let it fly and it locks up. I am then able to pull the trigger and the round goes off.

If I single feed, no issues. if I put 3-5 rounds in a magazine no issue. This testing is being done on the factory ammo and not the reloads.

I have played with the gas system and dialed it in so that it is cycling fine and putting the brass at about the 4-5 O-clock position in a nice little pile.

I have tried different buffer springs to see if a stiffer spring would aid in lockup but it has not. I went to a different bolt carrier group and tried that on both springs and that didn't help either.

I am into this about 500 rounds now and I am unable to get it to run a full 10 rounds without a failure. This is starting to get a little expensive to figure out.

This problem will occur on reloads and factory ammo.

If anyone has any suggestions please let me know, I am at a loss and not sure what to do next.

Thank you,

You have everything just about right and the best gas blockOpen up the Gas Nlock more..The best my 6mm ARC runs at is when bras hits at 3:30 to 4:00..Your magazine lips may n eed adjusted.But try the gas block 1st.Good Luck.

 

[BamBam1200]

Sounds like to me its a mag issue. The more pressure you put on the spring. It fails somewhere to operate normally. Try taking mag apart. Inspect the spring. I am in the process of building a 6mm arc also.

 

[762x51]

The brass only had a minor ding on the case mouth so I thought all was working well. The bolt locks open after the last round as well.

View attachment 355993

I've noticed the same flat dent on my cases on most of my gas guns. 6.5 grendel, creedmoor, 5.56. i'm assuming it's occuring during extraction and/or it's hitting the shell deflector.

glad you fixed it. i use metal mags on my grendel and may look into bending the lips of the mag to prevent issues down the line.

nice group too! only my creedmoor will shoot that well. everything else is an MOA at 100.

 

[Olskoolgman]

I agree with the mag issue. My arc is very finiky and i have only one mag that is truly reliable. It had a burr on the front where the fold seam was grabbing the the bullets and not allowing them to chamber. I used a dremel to round off the seam, and i lowered the front of the mag to allow for more tip clearance. It angles my rounds up and it cleared up my failure to lock into battery. problems. I also use 6.5 grendel brass and i have to really size it down with wilson bushing die and a redding shell holder that reduces headspace.

 

[chav0_12]

I know I was having slight feeding/cycling issues with my 6.5 Grendel and haven't had a single issue since switching to an Alexander Arms magazine. First mag was an ASC.

 

[Mmac52280]

I hesitated to comment, but I have had the identical problem with my 45 Raptor, but it's based on the AR-10 platform. A standard mag is modified with a front filler and a converted follower. I found some mags would bend enough in the middle, they couldn't go in the mag well. Vertical pressure from the spring applies all of the pressure at the very feed lips that guide the round into the chamber. We looked at multiple mags and settled on trying those that used the largest or widest indents on the sides. The indents stiffen the mag sides. That helped. We then tried an old backyard Racer's trick, we packed them in dry ice, 3 times. Poor man's heat treatment used to harden axles. If nothing else, the look of complete astonishment on a young helper's face, is so worth it.

The hardened metal distorts far less under load.

Much better, and I now have 1 20 round mag I can load 15 rounds in that shoots without an issue. Above 15 rounds and it may have a hang up. So my experience is that customized AR's need better mags, built for that round. Changing the round, changes the forces applied to the mag. We did tweak the feed ramps prior to hardening.

 

[arch408]

I read a while back that the 6mm ARC had feeding problems and there was one magazine brand that did not have that problem.I wish I could remember which one it was because i haven't gotten around to building mine yet. I'll have to see if I can find that article.

 

[kfreeze]

Good Morning, I am wondering if any of you AR-15 experts can help me out with an issue I am having.

Here are the Gun Spec:
6mm ARC, Factory ammo 108gr ELDM or handloads @ (108gr ELDX, BR4 primer, leverrevolution, at 2,732 fps)
Bartline 24" barrel 1:7 twist
Triggertec Diamond 2 stage trigger
Carbine length buffer with a standard 3 oz buffer
6.5 Grendal bolt Gen 2 verified with face depth measurement
Tried both standard spring and +15% power wolf spring
Superlative arms adjustable gas block. Rifle +2" gas system .092" gas port
CMMG and ASC metal magazine both 10 and 15 round

So here is what is going on.
Start with the gas block turned out about 4.5 turns per factory specs.
Place a round in the magazine. it fires and the bolt locks open. I clean the barrel and repeat. I work my way up to 3-5 shot groups and repeat. Everything cycles fine and the guns shoot well. Shoot 5 shot strings to 100 rounds. At this point I have not shot the gun with more than 5 rounds in the magazines.

Then I do load development on some ELDX and Leverrevolution powder. Shooting 3-5 shot groups it works just fine. This is across 6 different magazines all 10-15 rounders.

Now I am around 200 rounds down the tube.

This gun is setup for PRS and is going to be my daughters gun for this season. Now we are going to try and run a normal 10 shot stage. start shooting the gun. around shots 5-7 I will get a failure for the bolt to lockup up / go into battery. In some cases I am able to hit the forward assist and close it, then fire the gun. Other times the round is not far enough out of the magazine to allow that to happen. In some cases it is close to going into battery and when you pull the trigger it just goes click. If I drop the magazine, I am able to pull the charging handle, let it fly and it locks up. I am then able to pull the trigger and the round goes off.

If I single feed, no issues. if I put 3-5 rounds in a magazine no issue. This testing is being done on the factory ammo and not the reloads.

I have played with the gas system and dialed it in so that it is cycling fine and putting the brass at about the 4-5 O-clock position in a nice little pile.

I have tried different buffer springs to see if a stiffer spring would aid in lockup but it has not. I went to a different bolt carrier group and tried that on both springs and that didn't help either.

I am into this about 500 rounds now and I am unable to get it to run a full 10 rounds without a failure. This is starting to get a little expensive to figure out.

This problem will occur on reloads and factory ammo.

If anyone has any suggestions please let me know, I am at a loss and not sure what to do next.

Thank you,

Open the gas block up a little more. The +2" gas system isn't really your friend and under gassed has caused stuff like that for me before. Edit just read the whole post. You may want to have the gas port opened up a little or try loading ammo with the slowest burning powder listed in the manual to give you more gas with the longer gas system.

 

[cohunt]

Hmm, 9 posts so far after the op has it fixed ( since tuesday) --- I often wonder if people read all the posts in a thread--- I guess I know the answer ;-)

 

[762x51]

Hmm, 9 posts so far after the op has it fixed ( since tuesday) --- I often wonder if people read all the posts in a thread--- I guess I know the answer ;-)

there's 3 pages of comments, i wouldnt read through them all either LOL