DPMS AR-10 LR-.308 Cycle Failure

[Paradox]

Lol. I know right. A block is going to help you restrict your gas and a heavier buffer is going to help control it. I just went heavier buffer and glad i did. Fixed the issue and softened the recoil. I wish you luck but if your short stroking like i was restricting the gas is just going to make it worse hopefully thats not the issue. Good luck and let me know how it works out

Well it seems i fixed it. I polished a few rough spot and the rail points very lightly with some emery cloth, soaked the disassembled bolt in a pan of Rotella Diesel oil over night, then let it drain off another night, reassembled and Ran 100 rounds through and discovered one more use for the worlds most versatile oil lol. Was it the oil?, the polish? Who knows, probably just running the bitch like an oil slick but works now for site lol

 

[Fighting the good fight]

Well it seems i fixed it. I polished a few rough spot and the rail points very lightly with some emery cloth, soaked the disassembled bolt in a pan of Rotella Diesel oil over night, then let it drain off another night, reassembled and Ran 100 rounds through and discovered one more use for the worlds most versatile oil lol. Was it the oil?, the polish? Who knows, probably just running the bitch like an oil slick but works now for site lol

Good to here brother. Simple fix. Lots of oil and you helped break it in with some elbow grease instead of wasted round and smashed up brass

 

[Fighting the good fight]

Good to here brother. Simple fix. Lots of oil and you helped break it in with some elbow grease instead of wasted round and smashed up brass

I know that bcg smelled great cooking that shit off of it. Lol

 

[NCHillbilly]

I'm a little late to this thread, but had something to add, and a question of my own.

I recently built an LR 308, and had a few minor issues. First, it wouldn't strip rds from the mag. Found out that I had an ar-15 buffer, which was too long to let the bcg travel rearward far enough for the bolt to catch the rim of the next rd. The buffer came in a kit with the tube, spring, buffer, and stock. Moral of that story: Make sure to get LR 308 specific parts. I replaced the buffer with a KVP 5.6oz buffer and sprinco orange spring. BCG travels all the way back now.

Second issue: Took it out friday to see if the problem was taken care of. I took two different mags than I had used before. These were ASC mags ( the previous mags were p- mags). I have always had good luck with ASC's in other calibers, but these just would not function. I couldn't seat the mag ( even empty) with the bolt closed, and when I did try to run it, the bcg would drag to the point that it affected ejection.

I dropped the mag and single loaded it and it ran fine. Of course I didn't think to bring different brand mags with me that day. but when I got home, I tried p- mags and DPMS brand mags, and the bcg seems to travel with no drag.

Has anyone else had problems with the ASC mags? Has anyone modified or know of a fix for this particular issue?

After hearing all of the horror stories about large frame gassers, I feel optimistic that my issues are minor, but they gotta be fixed. A gun that won't run is useless.

 

[Evintos]

ASC mags are normally ok (not great though) but sometimes they require a lil tweaking of the feed lips.

- Fig 1. Insert empty magazine, pull bolt to rear until the lug contacts the follower (don't pull all the way back until it catches on the bolt catch). Inspect to see that both side feed lips sit between the bolt lugs.

- Fig 2. Remove BCG from receiver, stand it vertically, place magazine under BCG. Ensure there is clearance between feed lip and bolt carrier ramp. Note - If the gap with the follower is very narrow, you may want to remove follower and sit the carrier in between the feed lips more to see if there is adequate clearance. In my example, more than adequate.

1. Feed lip gap too narrow or too wide causing dragging on bolt carrier hammer ramp area or bolt lugs, you'll see wear marks on the edges of feed lips - Solution bend feed lips if possible, if bending it would make the feed lips too tall, file the inner edges of the feed lip to remove some material. Rear feed lip gap should be roughly 0.570", front feed lip gap roughly 0.595".

2. Top portion of feed lips causing rubbing on bolt carrier or bolt lugs either due to excessive material length or improper feed lip radius/curvature. You'll see wear marks on the top of feed lips and the feed lip radius. Solution - bend feed lips if possible, otherwise file material off feed lips and bend. Procedure not recommended it'd be hard to get the correct radius. Better to return to manufacturer for warranty or refund.

3. Nothing wrong with the feed lips length or geometry but the magazine's catch hole/recess for the catch is cut too low (causing magazine to require deeper insertion before it catches) relative to your lower receiver magazine catch position. You will see wear marks similar to #2. -File top edge of magazine catch hole/recess however you can have excessive vertical slop which can cause feed issues or other issues like failure to lock back on empty. Procedure not recommended. Better to return to manufacturer for warranty or refund.

Fig 1.

Fig 2.

Fig 3.

 

[NCHillbilly]

I'll definitely check those things. The mags are factory cerakoted, and there is visible wear marks on the edge of the feed lips. I've sent an e- mail to ASC to see what they say, but I have three of those mags, so I may play with one and see what happens.

 

[NCHillbilly]

ASC mags are normally ok (not great though) but sometimes they require a lil tweaking of the feed lips.

- Fig 1. Insert empty magazine, pull bolt to rear until the lug contacts the follower (don't pull all the way back until it catches on the bolt catch). Inspect to see that both side feed lips sit between the bolt lugs.

- Fig 2. Remove BCG from receiver, stand it vertically, place magazine under BCG. Ensure there is clearance between feed lip and bolt carrier ramp. Note - If the gap with the follower is very narrow, you may want to remove follower and sit the carrier in between the feed lips more to see if there is adequate clearance. In my example, more than adequate.

1. Feed lip gap too narrow or too wide causing dragging on bolt carrier hammer ramp area or bolt lugs, you'll see wear marks on the edges of feed lips - Solution bend feed lips if possible, if bending it would make the feed lips too tall, file the inner edges of the feed lip to remove some material. Rear feed lip gap should be roughly 0.570", front feed lip gap roughly 0.595".

2. Top portion of feed lips causing rubbing on bolt carrier or bolt lugs either due to excessive material length or improper feed lip radius/curvature. You'll see wear marks on the top of feed lips and the feed lip radius. Solution - bend feed lips if possible, otherwise file material off feed lips and bend. Procedure not recommended it'd be hard to get the correct radius. Better to return to manufacturer for warranty or refund.

3. Nothing wrong with the feed lips length or geometry but the magazine's catch hole/recess for the catch is cut too low (causing magazine to require deeper insertion before it catches) relative to your lower receiver magazine catch position. You will see wear marks similar to #2. -File top edge of magazine catch hole/recess however you can have excessive vertical slop which can cause feed issues or other issues like failure to lock back on empty. Procedure not recommended. Better to return to manufacturer for warranty or refund.

Fig 1.
View attachment 7856031

Fig 2.
View attachment 7856038

Fig 3.
View attachment 7856050

Just finished filing the feed lips on one mag. Rear gap is .550", front gap is .570", now the mag seats and there is no drag on the bcg. Good call. Thanks. I think that's all they need.

 

[Fighting the good fight]

Just finished filing the feed lips on one mag. Rear gap is .550", front gap is .570", now the mag seats and there is no drag on the bcg. Good call. Thanks. I think that's all they need.

Just read all that. Thats some good shit right there that would have been the last thing i thought of if i ever figured it out at all with the the feed lips. Good call

 

[NCHillbilly]

Just read all that. Thats some good shit right there that would have been the last thing i thought of if i ever figured it out at all with the the feed lips. Good call

That's why I come here first when I have issues. There's a lot of folks much smarter than I am, who hangs out on here.

 

[Paradox]

I'm a little late to this thread, but had something to add, and a question of my own.

I recently built an LR 308, and had a few minor issues. First, it wouldn't strip rds from the mag. Found out that I had an ar-15 buffer, which was too long to let the bcg travel rearward far enough for the bolt to catch the rim of the next rd. The buffer came in a kit with the tube, spring, buffer, and stock. Moral of that story: Make sure to get LR 308 specific parts. I replaced the buffer with a KVP 5.6oz buffer and sprinco orange spring. BCG travels all the way back now.

Second issue: Took it out friday to see if the problem was taken care of. I took two different mags than I had used before. These were ASC mags ( the previous mags were p- mags). I have always had good luck with ASC's in other calibers, but these just would not function. I couldn't seat the mag ( even empty) with the bolt closed, and when I did try to run it, the bcg would drag to the point that it affected ejection.

I dropped the mag and single loaded it and it ran fine. Of course I didn't think to bring different brand mags with me that day. but when I got home, I tried p- mags and DPMS brand mags, and the bcg seems to travel with no drag.

Has anyone else had problems with the ASC mags? Has anyone modified or know of a fix for this particular issue?

After hearing all of the horror stories about large frame gassers, I feel optimistic that my issues are minor, but they gotta be fixed. A gun that won't run is useless.

I think it’s more of the gun I found mine brand new in the box was built somewhere around 03 or four I think and I’ll fire one round and then not pick up the next so after Lane questions and then three weeks at a gunsmith it couldn’t figure it out which obviously wasn’t very good gunsmith I took it back pull the bcg disassembled it looked over the magnifying glass and found had a lot of rough spots on it from machining so I got a little emery cloth , dumped it in a bucket of oil, Overnight, let the oil drain off and I’ll,all then oiled, the living shit out of it no w it fires anything beautifully I think the first thing everyone goes for is the gas block or it’s under Gassed or or overgassed, or some similar issue but mine was firing and then write out around 4 -430 o’clock so I figured it had to be something else also I know a lot of people mess with the buffers I thought about it but one of not having to in the end so I don’t know if that would’ve helped in the end anyway but it does seem to anyone I’ve ever run into that is on one of these guns is had a problem and the funny thing is this is the only AR style rifle I’ve ever Owned that was a factory rifle and show only one that had issues all the others that I built myself out of scrap parts here and they’re all work fine and this was the one that decided to give me a hard time so go figure. Drown the thing in oil and see what happens

 

[NCHillbilly]

I think it’s more of the gun I found mine brand new in the box was built somewhere around 03 or four I think and I’ll fire one round and then not pick up the next so after Lane questions and then three weeks at a gunsmith it couldn’t figure it out which obviously wasn’t very good gunsmith I took it back pull the bcg disassembled it looked over the magnifying glass and found had a lot of rough spots on it from machining so I got a little emery cloth , dumped it in a bucket of oil, Overnight, let the oil drain off and I’ll,all then oiled, the living shit out of it no w it fires anything beautifully I think the first thing everyone goes for is the gas block or it’s under Gassed or or overgassed, or some similar issue but mine was firing and then write out around 4 -430 o’clock so I figured it had to be something else also I know a lot of people mess with the buffers I thought about it but one of not having to in the end so I don’t know if that would’ve helped in the end anyway but it does seem to anyone I’ve ever run into that is on one of these guns is had a problem and the funny thing is this is the only AR style rifle I’ve ever Owned that was a factory rifle and show only one that had issues all the others that I built myself out of scrap parts here and they’re all work fine and this was the one that decided to give me a hard time so go figure. Drown the thing in oil and see what happens

Huh?

I figured out my issues. First issue was fixed with a correct length buffer (2.5"), and the second issue was fixed by opening up the feed lip gap on my ASC mags.