AR-10 ejection issues

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  • lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Any advice would be appreciated on this.

    First time up to batt, A4 buffer tube, 308 buffer, 308 coil spring, 18" mid length barrel (Classic Firearms), non-adjustable gas block, Brownell's 308 BCG.

    About every 3-4 rounds with brass cased ammo (M80 and 168gr BTHP) I was getting a stove pipe that would jam between the next round and the roof of the upper, generally badly bending the round that was loading in to the chamber. Wolf had it happen once (maybe twice?) out of 20 rounds.

    I figured reading other stuff that it was over gassed.

    So, up next, I got an adjustable gas block and a Strike Industry flat spring (a bunch of other stuff, but that is the ONLY thing related to the gas or action).

    Closed off the AGB, no cycling. Opened it progressively using Wolf ammo till it cycled and held the bolt back. Opened another quarter turn, locked it down. Ran a few rounds of brass case and wolf and good. Put the handguard back on. Ran a 10 round mag of Magtech M80. 2nd to last round stove piped and jammed up the final round from the magazine. Everything is ejecting to 3 o'clock.

    I backed off the AGB a turn, failed to cycle fully, progressively opened it little by little. Got it functioning, 1/8th turn. Back to ejecting to 3 o'clock, but I did notice BEFORE that 1/8th turn, some of the wolf was ending up backwards in the receiver sitting on top of the empty magazine. The extra 1/8th turn seemed to get it to eject okay.

    I ran about 15-18 more rounds of brass case and ran almost all fine. It failed to pick up a round after the first shot on a 4 round magazine. Seemed like that could have been failure to seat the magazine properly. It DID eject the 1st round clear to my 3 o'clock fine. Just failed to strip the next round. A mag slap, pull the bolt and fired the next 3 just fine.

    So, lots of words, but I wanted to try to describe everything the best I can.

    My next thought is maybe it is the ejector. Too strong of an ejector spring? Is that a thing? Options? Take it out and cut part of a coil off? Should I get a 2nd one and compare it to what is in there? If so suggestions in the best option for an AR-10?

    I'd think if the bolt isn't coming back super fast or super hard, that if a case is ending up in the receiver backwards, that perhaps the ejector is slamming the case too hard.

    The extractor does appear to be holding cases well.

    Thanks!
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    If it helps any, I pulled it part and measured all the things (that I could think of). The BCG at maximum retraction is .125" exactly out of the buffer tube. I am trying to remember the distance from the bolt hold open. Hard to measure (with my calipers anyway). but looks to be around .215" (now I am trying to remember. Its a fraction over 3/16"). No indication that the BCG is striking the lower receiver/extension.

    One thing I do notice is extracting a case manually and slowly, both empty cases and dummy rounds sometimes turn around and fall back in to the chamber when I extract them slowly as the dummy tip or case mouth pass the front of the ejection port and can pop free. Any idea if that is a sign of too much ejector spring tension? It seems to take a lot of force to retract it with a punch (I can). At least compared to two AR-15 ejectors I tested. Extractor as mentioned in my first post very easily holds a case in place using the tip of my finger to twist it in to place. Also seems to take more force holding the case tip on to the bolt face compared to an AR-15.

    Would ejector spring length be any indication of force? I realize it could be a different material or thicker coils which would be really damned hard to figure out. I found something somewhere else that seemed to indicate for an Armalite AR-10 it should be between .95" and 1.15" in length. No I have not taken the trouble to pop my ejector out yet.

    I am still leaning towards getting a new ejector spring (or two?). Recommended brands? I see LMT and Sprinco sprinkled around. I've heard of LMT and they seem to have a good reputation. Sprinco rings a bell, but not sure of their reputation. Then with a new one in hand, try comparing to my existing one. Both force and length. Try trimming my spring a coil or two and then take it to the range.

    BTW shooting off hand standing, the 4 rounds I shot, went to about my 2:30. I was standing about a foot back from the edge of the bench and 3ft to the side. One landed on the bench, 1 hit the edge and fell off. The other 2 landed just in front of the shed.

    All went roughly 5ft to the side from standing height.

    With the gas block shut a little more so that the bolt hold open was not engaging, but it was ejecting cases, it was ejecting to about the 1:30. Not sure if that tells anyone anything about the ejector.

    When it was fully gassed with the non-adjustable it was hurling them to the 1:30-2:30, but a lot further. About 10-14ft from a sitting position on the bench.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Lastly this is what the brass looks like. Brass doesn’t appear messed up. Read of the case appears to have a just visible indent, I am guessing from the ejector at the 12 o’clock position. Most of the brass has the same mark.

    I don’t see anything obvious on the rim, back, side or front that the extractor is tearing it up.
     

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    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,819
    Laz, I've never built nor shot an AR10. Plenty of experience with its little brother though. Usually, that kind of 'touchyness' has been attributed to BCG(in respect to AR15s). I know you have other AR10s. Are they of the same 'family'? Have you tried a different BCG? It might be, your BCG could use some reliability work.
    Again, not familiar with AR10s.
     

    slsc98

    Ultimate Member
    May 24, 2012
    6,750
    Escaped MD-stan to WNC Smokies
    While you’re trying stuff, pickup a Lancer Warfighter mag. Just about EVERYthing you describe is exactly what I was going through with my brand new DPMS GII ... buddy insisted I ditch the MagPul (came w the gun from DOMS) and other LR mags I was trying.

    Have not had so much as a hiccup since ... fwiw and ymmv, best o’ success!
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Laz, I've never built nor shot an AR10. Plenty of experience with its little brother though. Usually, that kind of 'touchyness' has been attributed to BCG(in respect to AR15s). I know you have other AR10s. Are they of the same 'family'? Have you tried a different BCG? It might be, your BCG could use some reliability work.
    Again, not familiar with AR10s.

    I’ve got AR-15s PHD, but this is my only AR-10 (so far) sadly. Yeah at this point I am thinking it’s something with the BCG. Kind of thinking I might just swap extractor, ejector and the springs for them. Suggestions on whose I should go with would be great. Or if I am just better of buying a new complete bolt (preferably nitrided) either for quality reasons or because the cost is going to be close.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,819
    ...and for those chasing down problems in ARs, it can be a long trail to follow at times. Do yourselves a favor and only change one thing at a time between range trips. It may seem to take a long time, but in the long run, it will actually help avoid a lot of wild goose chases.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,819
    I’ve got AR-15s PHD, but this is my only AR-10 (so far) sadly. Yeah at this point I am thinking it’s something with the BCG. Kind of thinking I might just swap extractor, ejector and the springs for them. Suggestions on whose I should go with would be great. Or if I am just better of buying a new complete bolt (preferably nitrided) either for quality reasons or because the cost is going to be close.
    Oh dang, thought you had more than one. My bad.
     

    qorban88

    Active Member
    Jan 11, 2015
    106
    I had the same problem with several AR10's I built with varying configurations. It was partially over gassed, which I corrected with an adjustable gas block, but I eliminated all the remaining issues after ditching the Brownells BCG; I believe it was the extractor. Switched to a Toolcraft DLC BCG and haven't had any more issues. Personally, I don't see how the magazine has anything to do with extraction and ejection.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,819
    I had the same problem with several AR10's I built with varying configurations. It was partially over gassing, which I corrected with an adjustable gas block, but I eliminated all the remaining issues after ditching the Brownells BCG; I believe it was the extractor. Switched to a Toolcraft DLC BCG and haven't had any more issues.
    Toolcrafts are good stuff.

    I have taken POS BCGs and done work on them and overcame the inherent problems attributed to them. Main thing is pulling the keys, stoning them flat, then resealing them and properly torquing them. That alone, will usually get you back on the range, at least.
     

    jamesp15

    Active Member
    Jul 16, 2018
    420
    Southern PG
    I had a similar issue, and a thread on here about it.
    In the end to fix it I had to do 2 things. One was my chamber was ROUGH, I had the maker (Faxon) replace it with a new one. That made it work better but then to get it going 100% I had to add a second O-ring under the extractor. Since I did that it has run 100%, approx 300 rounds through it now without issue. (Federal M80 7.62 as well as Federal Premium and Non-Typical .308 150grain)

    https://www.mdshooters.com/showthread.php?t=237729
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Geez, that sounds like a lot of problems.

    My money is strongly on your barrel being trash, both in terms of the finishing and the gas port being too large. IIRC, Classic's barrels are made BCA, and BCA has a super poor rep in the industry. People need to stop building ARs and skimping on the barrel, that is maybe the MOST important element of your gun to have high quality.

    You also need to try a new magazine.
     

    woodline

    Ultimate Member
    MDS Supporter
    Jan 8, 2017
    1,947
    To start with I expect the chamber on that BCA barrel is tight and/or rough. And probably the extractor needs to be replaced.

    Possibly why steel cased ammo works better than brass cased ammo.
     

    DavidA

    The Master of Disaster
    Dec 6, 2013
    371
    Annapolis
    My guess having built four LR308’s is that it is the BOLT, I have only used either AERO precision or Tool Craft Bolt carrier groups. All my barrels are Black Hole weaponry. No cycling issues. The only issue I had was when firing really heavy bullets, 225 gr Hornady HPBT. My brass was getting trashed. It was hitting the defector so hard it was beating up the necks and shoulders off the brass. My first solution for this was a piece of adhesive backed Velcro that basically cushioned the impact of the brass on the deflector. Ultimately I just got a adjustable gas block to slow down the bolt carrier group.

    To me it appears that the ejector spring in the bolt is to heavy causing the spent casing to spin so fast that the necks are past perpendicular even hitting the port opening first. Therefore causing the case to deflect back into the ejection port. You can test this theory by having someone close to you lend you a bolt or a complete BCG that does not have cycling issues. Just my two cents.


    Sent from my iPad using Tapatalk
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    My guess having built four LR308’s is that it is the BOLT, I have only used either AERO precision or Tool Craft Bolt carrier groups. All my barrels are Black Hole weaponry. No cycling issues. The only issue I had was when firing really heavy bullets, 225 gr Hornady HPBT. My brass was getting trashed. It was hitting the defector so hard it was beating up the necks and shoulders off the brass. My first solution for this was a piece of adhesive backed Velcro that basically cushioned the impact of the brass on the deflector. Ultimately I just got a adjustable gas block to slow down the bolt carrier group.

    To me it appears that the ejector spring in the bolt is to heavy causing the spent casing to spin so fast that the necks are past perpendicular even hitting the port opening first. Therefore causing the case to deflect back into the ejection port. You can test this theory by having someone close to you lend you a bolt or a complete BCG that does not have cycling issues. Just my two cents.


    Sent from my iPad using Tapatalk

    That’s my guess, ejector spring. Chamber doesn’t appear rough Or tight to my eye. Loaded ammunition drops in. Extracts easily (a bit tight unlocking the bolt, but I think it might the gas rings. Bolts tight to cam with the BCG out). I guess it could be the extractor. Seems tight with good tension. Brass isn’t getting marred up.

    Guns accurate as heck. It’s shooting sub MOA with PPU 168gr match. About 1.5 with Magtech and 2 with Wolf. I realize accuracy doesn’t necessarily mean something can’t be wrong with the chamber.

    Got the barrel half because I was collecting parts for a “some day build” and worried maybe crap would get banned or really hard to source some day. If I have to I’ll get a Faxon. That’s likely what I am doing with my next AR-15 build.

    Ordered a JP ejector and spring to try. That doesn’t work, I’ll probably go ahead and just get a toolcraft BCG.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Not sure if the pics here help any. Brass looks almost unfired from the side.

    Also all of the fired brass is within case length for SAMMI specs still (using a case gauge and my calipers). Nothing stretched too much. Don’t really want to pull apart a live cart until I have my .308 dies setup to put it back together. So hard to measure existing case length.
     

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    lazarus

    Ultimate Member
    Jun 23, 2015
    13,680
    Also double checked the chamber. Cartridge drops in easy and to the shoulder. Drops out easy. Even after giving the cart a good tap with a little rubber mallet on the back of it, it drops back out fine.
     

    DavidA

    The Master of Disaster
    Dec 6, 2013
    371
    Annapolis
    Just for shit and giggles you could pull the existing ejector spring and cut it to reduce its length slightly. This would decrease the ejector force and slow down the rotation of the ejected cartridge. You are getting a new spring anyway and for me it is solving these problems that is really the fun of doing your own build. Looking at all your photos and what you have done I do not believe it it’s a chamber issue. Good luck update us.


    Sent from my iPad using Tapatalk
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,819
    For my range toys, I cut the ejector spring so that my brass winds up in a nice pile next to me.
    Interesting. Sort of a poor man's adjustable gas block?


    I have my 300blk SBR so tuned, the brass all ejects to within a 12" circle at 4 o'clock.
     

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