I have the DPMS Panther Ar -10 (LR .308). When I release the BCG and load the first round with no problem. When I discharge the first round the round does not get ejected. I feel the recoil and it sounds like the BCG goes back and forward again without ejecting the shell or reload the second round. The dust over is pushed down, so it seems to cycle bust doesn't. I have read alot of the post on the LR308, however I didn't see ant with this problem, some similar but not specific. Any one a potential solution?
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DPMS AR-10 LR-.308 Cycle Failure
- Thread starter Jim/Woods3ofus@inwvheaven
- Start date
Your BCG likely isn't cycling all the way back. Enough to pop the dust cover, and feel the BCG moving, but probably not enough for the case to clear the chamber, much less eject. Not enough gas to cycle the bolt is usually the root cause, but it could be the buffer weight, gas tube impingement or undersized gas port, among other things.
There are others much more knowledgeable than I on the LR308 platform, but my own experience with DPMS in 6.5CM left me...disappointed. It's now an $1100 paper weight in the back of my safe. Just too unreliable for matches, hunting or (God forbid) self defense.
There are others much more knowledgeable than I on the LR308 platform, but my own experience with DPMS in 6.5CM left me...disappointed. It's now an $1100 paper weight in the back of my safe. Just too unreliable for matches, hunting or (God forbid) self defense.
Took my buffer and buffer spring out and measured them. The buffer is appox. 2 and 7/16 inches and the spring measured approx. 11 inches. Does this sound right to you Gunny?
Length isn't the critical part for the buffer, weight is. As to the spring, it also depends on the diameter of the spring wire. All of this determines resistance, as the bolt unlocks, and the BCG starts to travel back; as the gas comes down the gas tube, through the BCG key, and down into the rear bolt head where the gas rings reside. This gas blows the bolt back (causing the cam to rotate and unlock the bolt itself from the receiver) and excess gas is blown out the side through the two holes in the scalloped side of the BCG.
Anything that retards the bolt (buffer, spring, bent gas tube, grit in the action, etc.) will slow that BCG down. Sometimes enough to not push it back far enough to eject, and if worse, not far enough to pick up the next round off the mag. Sounds like yours is seriously under gassed (just WAG from here on a keyboard), and/or seriously retarded (as in sluggish, not left wing brain dead).
Like mentioned previously, I am AR/LR literate, but not by any means an expert. There's some on here who are whizzes at tweaking these platforms. I tend to treat them as they were designed; part swap troubleshot, mass produced, modular platforms.
Anything that retards the bolt (buffer, spring, bent gas tube, grit in the action, etc.) will slow that BCG down. Sometimes enough to not push it back far enough to eject, and if worse, not far enough to pick up the next round off the mag. Sounds like yours is seriously under gassed (just WAG from here on a keyboard), and/or seriously retarded (as in sluggish, not left wing brain dead).
Like mentioned previously, I am AR/LR literate, but not by any means an expert. There's some on here who are whizzes at tweaking these platforms. I tend to treat them as they were designed; part swap troubleshot, mass produced, modular platforms.
Diagnostic steps for you.
1. remove upper, remove bolt from bolt carrier, remove charging handle, insert carrier sans bolt into receiver and check that it moves freely back and forth with gravity. Reinstall upper onto lower, remove buffer and spring, reinstall charging handle with the bolt carrier sans bolt. With gravity, bolt carrier should freely move backwards and forwards into and out of the receiver extension. Inspect gas key to ensure it's secured. Check for gas flow, with the bolt removed, insert copper wire through gas key and visually check for the wire inside the bolt carrier.
2. With bolt removed, insert bolt into the barrel extension and rotate, it should rotate 360 degrees freely without binding. It should also insert freely. Check headspace.
3. Inspect gas tube for damage. If you have a borescope, check for the presence of a gas port and inspect alignment. If you don't have a borescope but have compressed air, take compressed air, and place tissue on muzzle, put finger to block the chamber, blow compressed air through the gas tube. If you see the tissue move, there is gas flow. If you don't see it move, either the gas port is blocked, not drilled, the gas block and gas port are misaligned or there is an obstructed gas tube.
4. Test fire single round without magazine and watch for ejection. Test fire single round with empty magazine. If both passes, test fire 1 round with full magazine. Depending on tolerances, the magazine catch may be ever so slightly high enough that a full mag puts pressure on the underside of the bolt carrier and prevent cycling.
5. If it fails to cycle with previous testing. Weigh the current buffer. Weights can be anywhere from 3.5oz to 5.8oz. Assuming your buffer weight is at max, punch out the roll pin and remove 1 internal weight. Alternatively, buy lighter weight buffers for testing. Repeat test 4.
Edited to add - if you find that the firearm cycles fine with a lowered buffer weight, buy a lighter weight buffer. Do not continue to shoot with the buffer missing a weight inside.
1. remove upper, remove bolt from bolt carrier, remove charging handle, insert carrier sans bolt into receiver and check that it moves freely back and forth with gravity. Reinstall upper onto lower, remove buffer and spring, reinstall charging handle with the bolt carrier sans bolt. With gravity, bolt carrier should freely move backwards and forwards into and out of the receiver extension. Inspect gas key to ensure it's secured. Check for gas flow, with the bolt removed, insert copper wire through gas key and visually check for the wire inside the bolt carrier.
2. With bolt removed, insert bolt into the barrel extension and rotate, it should rotate 360 degrees freely without binding. It should also insert freely. Check headspace.
3. Inspect gas tube for damage. If you have a borescope, check for the presence of a gas port and inspect alignment. If you don't have a borescope but have compressed air, take compressed air, and place tissue on muzzle, put finger to block the chamber, blow compressed air through the gas tube. If you see the tissue move, there is gas flow. If you don't see it move, either the gas port is blocked, not drilled, the gas block and gas port are misaligned or there is an obstructed gas tube.
4. Test fire single round without magazine and watch for ejection. Test fire single round with empty magazine. If both passes, test fire 1 round with full magazine. Depending on tolerances, the magazine catch may be ever so slightly high enough that a full mag puts pressure on the underside of the bolt carrier and prevent cycling.
5. If it fails to cycle with previous testing. Weigh the current buffer. Weights can be anywhere from 3.5oz to 5.8oz. Assuming your buffer weight is at max, punch out the roll pin and remove 1 internal weight. Alternatively, buy lighter weight buffers for testing. Repeat test 4.
Edited to add - if you find that the firearm cycles fine with a lowered buffer weight, buy a lighter weight buffer. Do not continue to shoot with the buffer missing a weight inside.
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Try the steps as Evintos suggested.
Know anyone with a DPMS style BCG and some headspace gauges? See if they’ll let you try their bcg.
Check the extractor and extractor spring.
Swap over to a Armalite receiver extension, spring, and buffer. You can get the whole kit from armalite for 75 bucks.
Know anyone with a DPMS style BCG and some headspace gauges? See if they’ll let you try their bcg.
Check the extractor and extractor spring.
Swap over to a Armalite receiver extension, spring, and buffer. You can get the whole kit from armalite for 75 bucks.
Evintos has some very good tests there, some of which I'd never thought of before.
I, on the other hand , have questions. What's the history on this gun, if you know any? Is this a new gun? A new build? A gun you've had for a while that maybe worked before and now it doesn't? A used gun you picked up somewhere?
If it's not new out of the box, there's a really good chance somebody may have been swapping parts, even without realizing it. For instance, if it has an AR15 buffer spring instead of a AR308 spring, it will have too many coils and won't allow the bolt carrier group to travel back all the way. I have inadvertently picked up the wrong spring and assembled the gun only to find it short-stroking a couple of weeks later. Took a while to track down the problem, then I had to figure out which AR15 had the 308 spring.
I, on the other hand , have questions. What's the history on this gun, if you know any? Is this a new gun? A new build? A gun you've had for a while that maybe worked before and now it doesn't? A used gun you picked up somewhere?
If it's not new out of the box, there's a really good chance somebody may have been swapping parts, even without realizing it. For instance, if it has an AR15 buffer spring instead of a AR308 spring, it will have too many coils and won't allow the bolt carrier group to travel back all the way. I have inadvertently picked up the wrong spring and assembled the gun only to find it short-stroking a couple of weeks later. Took a while to track down the problem, then I had to figure out which AR15 had the 308 spring.
How many rounds thorough the DPMS ? Is it new ... or new to you ? ( IE , used )
Have you cleaned the chamber of any packing oil ?
Large Frame AR's tend to need a little longer break in ... at least all the ones I have fired.
Look for any excess gas leakage at the gas block.
Have you cleaned the chamber of any packing oil ?
Large Frame AR's tend to need a little longer break in ... at least all the ones I have fired.
Look for any excess gas leakage at the gas block.
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make sure gas block is aligned, even the smallest misalignment can lead to issues
get a standard 308 spring and buffer of at least 5oz
get a standard 308 spring and buffer of at least 5oz
Years ago when I bought my LR-260H, it had the wrong buffer spring in it from DPMS. I swapped out the buffer spring, and it's ran great ever since. The only mods that I've ever made to the rifle were changed out the A2 stock to an ACE skeleton stock, put a good trigger in it, and installed a SLR adjustable gas block because I shoot with suppressor's.
My son had the same exact problem a couple years ago. He fixed the problem by replacing his extractor with the DPMS GII version.
The rifle has functioned perfectly since.
The rifle has functioned perfectly since.
Thanks everyone for the tips,tricks,and procedures. I will take all and fihure things out. I will post results at a later date.
That was my first thought was extractor. If its not pulling the spent case out of the breach its beyond under gassed. Im having an under gassed issue with my 22" 6.5CM complete upper i bought from aero this time last year. Its starting to cycle factory ammo better but my hand loads at almost max load with every powder for the 65 it short stroking. Either stove piping or it will eject properly but bolt wont go back far enough to pick up next round. Its got less then 100 rnds thru it cause im tired of it smashing my good brass. Thats a gas issue this seems to me like an extractor issue
If it was an extractor issue the bolt would be picking up the next round and attempting to chamber it.
It was short stroking and yeah it was not getting enough gas and no i didnt and still dont have an adjustable block on it yet but i went in the complete opposite direction. I actually went with a heavier buffer thinking the inertia of the weight and mass off the bolt and the pressures i was giving it would help carry the weight rearward and that worked perfectly. It cycles everything and runs great now and ive been able to step my charges back instead of going higher. I was at almost max load on every powder projectile primers known to man. Now she runs like a champ. Ran like 300 thru it this weekend the only malfunctions i had were with imr 4064 that i had loaded up a while back cause i was just trying everything i could but im all good now
In your case it sounds like it was bolt overrun which can present itself like short stroking. Basically, you were over gassed and your bcg was moving so fast reward that the extractor was ripping off the rim before it can fully pull the case out and the times it did extract (and eject) it was moving so fast forward that the magazine could not push the round up fast enough to load. Going higher on the charges exacerbated the problem. It's also possible the OP is having trouble with over gassing as well rather than undergassing.
That was my first thought so i was playing with different powders and and everything else and working loads up from starting to max and was having the same issues but factory stuff ran pretty good but not perfect. I still need a adjustable block and some more break in time. I put maybe a 100 rnds. Thru it and got to be more of a pain in the ass and ruining my brass so i put it to the side for a year and just pulled it back out and got it figured out i believe. I was loading a bunch of ladders in .3 from start to almost max and sometimes max with evry powder i have so i wasnt going from one extreme to another i was working everything in between i think it needed some more break in and for now the heavier buffer seemed to solve the problem until i get a new gas block
There is absolutely NOTHING wrong with leaving the heavy buffer in there EVEN WITH an adjustable gas block. Might consider going with a heavier spring as well.
IMO the adjustable gas blocks have their place but they also add another variable to the problem. I know this from experience throwing everything I could think of at a 308AR that was basically non-functional until it decided on it's own to work for a few rounds-just long enough for me to rejoice and think I'd found the problem. Then back to square one. In the windup I removed the adj gas block and put a plain ol' low profile fixed block on it and started concentrating on other areas. I knew damn well the market was flooded with over-gassed ARs that still worked flawlessly. Heavier buffer (5.6 oz) and a Sprinco orange spring were installed and then LEFT ALONE. Function improved a lot after that but not totally fixed. Moved on looking at other stuff and found out my bolt was causing a headspace problem. Replaced that and it ran like a champ ever since.
Whenever gas blocks are changed, especially to adjustable, there's a period of about 50-100 rounds (depends on how "dirty" your ammo is) required for "sealing" gaps. You'll see residue "leakage" around the gas block journal and as these gaps seal up, you'll have to adjust the gas block (either reducing flow a couple more clicks or bleeding off more) otherwise you'll end up right back at over gassed. You'll know if it's starting to seal up when your ejection pattern starts shifting forwards.
Once sealed up as long as the seal doesn't break, the adjustments won't need to be touched unless you're going from unsuppressed to suppressed, playing around different powders, or going low mass.
Headspacing is highly recommended for anyone assembling large frame AR since there's not really a set standard or TDP like for AR15 so one shouldn't expect plug and play.
Once sealed up as long as the seal doesn't break, the adjustments won't need to be touched unless you're going from unsuppressed to suppressed, playing around different powders, or going low mass.
Headspacing is highly recommended for anyone assembling large frame AR since there's not really a set standard or TDP like for AR15 so one shouldn't expect plug and play.
In the past ive only used adjustable block for my blackouts but right now my baby runs like a champ. I agree if its running great dont fix something thay isnt broke. Everyone was telling me to go in the other direction with lighter stuff i thought about it and went in the complete opposite. Lol just my nature and man im so pleased with it. I went with the 5.8 and love it. I was thinking maybe after some more breaking in i may go back to the standered buffer but it runs so much better now.
The so-called "standard" buffer in these DPMS, PSA, etc 308 ARs is really a standard AR15 buffer that weighs ~3 oz. They were designed for 223/556 systems. The original Armalite (not the same co as today) AR10 was designed to run a 5.4 oz buffer to handle the 308 round. That's the same weight as a H3 buffer. The extra weight slows down the reciprocal mass to a reasonable level making the gun much smoother and cutting down on recoil. Stick with the heavy buffer and tune your gas block to run with that. Reliability is what you were chasing so stick with what's proven to be reliable.
That was my whole thoght process and solution but i asked for a little advice on here witch was and is much appreciated and i got about 15 different answers and options from 10 different people so i went with my thoughts and gut and gotter. A few thought the way i was and everyone else said lighter but im just happy i got it figured out now and by going heavier im getting less recoil npt that that was an issue but its so comfortable to shoot now and can actually run good ladders and strings without having to worry about over pressure and under just trying to get it to cycle easy simple fix just had to think outside the box and thats what i needed. Even some of the wrong answers helped cause i knew they wernt correct but it got me thinking more so im very happy the ways shes running. I dont have an adjustable block at the moment depending on even getting one for this. I normally only use them with my BOs being that i have so many different loads and subs and everything else with those so they help alot there restricting the gas to where i want it but if she stays running they way she is. Im probably just going to hold off on the block unless i need one in the future. Its running everything perfectly and so comfortable. If it aint broke im not going to fix it but if the time comes i will go that route if need be. I really appreciate all the help and support from yall.
Glad you got it figured out as it sucks when a weapon won't function properly.
Well. You could have an extractor issue or possibly your bolt is moving so fast its just leaving the spent round but if your your BCG was cycling properly you would still be picking up another round out of the mag. And jamming so im leaning towards extractor issue
I would say extractor or your short stroking. I had an issue with short stroking everyone told me to go with a like lighter spring. I went in the opposite direction with heavier buffer to slow my bolt down and it worked perfectly fine afterwards. But if you're not picking up another round im and or leaving 1 in the chamber probably extractor or too hevy of a buffer set up. Are you using factory or handloads.
Clean your gun and bolt and get that bolt nice and wet and see what it does and then let us know
The first round fires and ejects fine right at 3-4 o’clock as it should, its just not catching the next round. Im gonna swap in a spare BCG and see what happens, or mess with the buffer weight, everything else looks fine, took bcg apart and all components appear to be good
Give it a nice clean and oil it all up pretty good sounds like your short stroking. The bolt is coming back just far enough to eject the round but not far enough back to strip the next round off the mag. A nice cleaning and oil can help a little i had the exact issue at one time. But ended up going with a heavier buffer after all else failed
Are they factory rounds or handloads and is it a brand new rifle or one you have been using. It might just need to be broken in a little. Seen that a few times as well
It might feel like your bcg is fully cycling but im willing to bet your short stroking. Cycling just enough to throw your spent rnd. But not go back that extra little bit to pick up the next. I would start by giving it a though cleaning and oil the shit out of it all and get some rnds through it to break it in
I just had the same issue not to long ago with a 22" 65. Everyone was telling me to go lighter on the spring anf adjustable gas block
Then i got to thinking and went in the complete opposite direction. I went with a heavier buffer thing the inertia of the gas bcg and heavier buffer would get the bcg back far enough to cycle probably and it work great never had an issue with it since. Sometimes you gotta think outside the box and keep it wet. Wetter the better
Then i got to thinking and went in the complete opposite direction. I went with a heavier buffer thing the inertia of the gas bcg and heavier buffer would get the bcg back far enough to cycle probably and it work great never had an issue with it since. Sometimes you gotta think outside the box and keep it wet. Wetter the better
I"m going to the range tomorrow, I tore everything down and oiled it good, on a side note, when i compared the DPMS BCG to spare i had, it was almost scary how rough the machining is on the DPMS piece, theres all sorts of tool marks and rough edges, I'll see what happens, and then try the spare bcg, and if that doesn't work i'll start looking at the buffer, and maybe take a weight out to lighten is a couple ounces, i'm also considering a different Gas Block as several people here and elsewhere have said its not a very good piece from the factory. It just drives me nuts as i've built many an AR and never had an issue, then I buy Factory gun and its a mess, lol I'll update soon
It's not strange. If the BCG is moving too fast the spring in the magazine doesn't have enough time to push the round up for it to feed into the chamber.
That's kind of surprising I'd agree. I can't remember how many clicks on something such as the SA AGB makes a full turn but if you were only two turns out from closed and went to four it'd be going from half open to full open gas port.
That was one of the reasons i went to a heavier buffer was to slow down the cyclic rate if that actully was the issue. I thought it was moving too fast or not going far enough back to eject every rnd. Or pick up every rnd i believe mine was short stroking. Either way the heavier buffer fixed it
Exact same thing. Always just build them. Buy an aero 22" 65 upper and had issues with it. I was going thru what u are now. I thought the bcg was going all the way back cause it would eject sometimes and or stope pipe and occasionally pick up the next rnd. But it was just one big malfunction. Everyone said adjustable block and light er spring. I used a heavier buffer and never had a malfunction since i put that heavier buffer in and runs great saved alot of unnecessary money. If the bcg machining is as bad as you say it is maybe you can debur it a little and clean it up some. Help break it in. Im still thinking a little breaking in and or heavy buffer youll be in good shape
I had planned on going to the range today, but got rained out, hopefully tomorrow and i'm going to bring a spare bolt and mess with the buffer weight, gotta be one or the other, if that does'nt do it all thats left is the Gas Block and thats cheap enough so hopefully it will be solved,, I just get pissed that after building so many ARs with no problem I finally get my ass handed to me with a damn FACTORY rifle, wtf, lol just crazy
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
would like to see a really good write up on effects of different buffer/ spring/ bcg/ gas combos. there is definitely a sweet spot for most combinations but occasionally one component takes you out of finding it.
on my 6.5cm I've settled on JP LMOS light weigh BCG, lightest spring/weight combo SCS and under half on gas. I've tried adding tungsten weights and stronger springs taking it beyond what full gas would allow and heavier buffer combos only increased recoil impulse.
on my 6.5cm I've settled on JP LMOS light weigh BCG, lightest spring/weight combo SCS and under half on gas. I've tried adding tungsten weights and stronger springs taking it beyond what full gas would allow and heavier buffer combos only increased recoil impulse.
My ideology is keep it simple. Once you start changing the components then you have the possibility of opening Pandora's box. Most and i say most components such as bcg typical spring buffer set up are widely sold because they are widely used because they are wildly known to work. Of course you can fine tune your rifle to be a little more the way you want it but standard components are known to be a good baseline to have an operational firearm. Once its operational and broken in then you can start fine tuning it by slightly changing this or that to soften up recoil or what have you. Thats just my 2 cents
Most of your components have certian weights for a reason and once you change one your other standard components are going to be needed to be changed or tuned as well so you can put yourself in a position to chasing your tale around in circles when all you did was create a problem that wasn't there to begin with. But there is nothing wrong with fine tuning your rifle the way you want it to run once you already have it running
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