AR10 - Jammed while in battery

The #1 community for Gun Owners of the Northeast

Member Benefits:

  • No ad networks!
  • Discuss all aspects of firearm ownership
  • Discuss anti-gun legislation
  • Buy, sell, and trade in the classified section
  • Chat with Local gun shops, ranges, trainers & other businesses
  • Discover free outdoor shooting areas
  • View up to date on firearm-related events
  • Share photos & video with other members
  • ...and so much more!
  • OP. One question. Do you case gauge every round you've reloaded? I'm not sure if this can cause such a problem, but out of every 1K rounds I reload, I get 4 or 5 rounds that refuse to case gauge. I've gone through the trouble of pulling the bullet and primer, resizing the brass, and reloading. Success rate for that runs about 50%.

    No, I don't. Actually, never have! Except for the earlier AR10 that had the ejector swipe problem, I was checking rounds when trying to track down that problem, which was solved with an adjustable gas block.

    Is that a standard practice?

    It is with me. I don't think everyone does. I load so many, I figure chances are, I'll have a problem if I don't.

    YMMV

    Sent from my SM-G965U using Tapatalk

    I look at it as a 2 second insurance policy.
     

    Digby

    Member
    Feb 19, 2014
    37
    Western Howard County
    While your problem can be brought on by excessive headspace or an improperly loaded round as others have suggested, it is far more probable that you experienced excessive port pressure brought on by the kind of powder that was used in the load in question.

    Powders have different pressure curves and the powder in that round looks like it caused too much pressure to pass through the gas tube which forced the carrier to begin rearward travel while the empty case was still expanded and pressing against the sides of the chamber (i.e., “obturated”). As the carrier moved back and the bolt began to rotate, the cartridge was still held rigidly in place by pressure. The rotating bolt, particularly the ejector and the extractor, deformed the very hot and malleable brass of the stuck cartridge. Ultimately, the excessive pressure had nowhere to go but through the primer pocket, causing the primer to drop.

    So while the symptoms scream “overpressure,” the problem is really a matter of improper timing. AR10s are famous for this kind of problem. The same ammunition in a different rifle, i.e., a bolt gun, or an AR with a longer gas system, might function just fine. The length and size of the gas tube, the size of the gas port, and the distance between the port and the chamber all play into the timing equation.

    If this is a factory load, then I would avoid using it again in your AR10. If it's a handload, you need to switch powders.
     

    rgramjet

    Ultimate Member
    Jan 25, 2009
    2,962
    Howard County
    I had an issue with my LAR8 failing to eject. Sent it to RRA and they determined the gas tube was detached.

    I'm not technical with AR uppers. Was interesting go hear that was the issue.

    FWIW
     

    John from MD

    American Patriot
    MDS Supporter
    May 12, 2005
    22,734
    Socialist State of Maryland
    While your problem can be brought on by excessive headspace or an improperly loaded round as others have suggested, it is far more probable that you experienced excessive port pressure brought on by the kind of powder that was used in the load in question.

    Powders have different pressure curves and the powder in that round looks like it caused too much pressure to pass through the gas tube which forced the carrier to begin rearward travel while the empty case was still expanded and pressing against the sides of the chamber (i.e., “obturated”). As the carrier moved back and the bolt began to rotate, the cartridge was still held rigidly in place by pressure. The rotating bolt, particularly the ejector and the extractor, deformed the very hot and malleable brass of the stuck cartridge. Ultimately, the excessive pressure had nowhere to go but through the primer pocket, causing the primer to drop.

    So while the symptoms scream “overpressure,” the problem is really a matter of improper timing. AR10s are famous for this kind of problem. The same ammunition in a different rifle, i.e., a bolt gun, or an AR with a longer gas system, might function just fine. The length and size of the gas tube, the size of the gas port, and the distance between the port and the chamber all play into the timing equation.

    If this is a factory load, then I would avoid using it again in your AR10. If it's a handload, you need to switch powders.

    Varget is used in the AR platform by the AMU as well as many of my fellow shooters. While it may not be good for the M1A, it works very well in the AR.
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    I look at it as a 2 second insurance policy.

    It is with me. I don't think everyone does. I load so many, I figure chances are, I'll have a problem if I don't.

    YMMV

    Sent from my SM-G965U using Tapatalk

    You got me to thinking so, just for grins I pulled a sampling of my handloads and checked. All good. Whew! But I think I'm going to put this step into my SOP anyhow.

    Thanks
     

    omegared24

    Ultimate Member
    Dec 23, 2011
    4,747
    Ijamsville, MD
    While your problem can be brought on by excessive headspace or an improperly loaded round as others have suggested, it is far more probable that you experienced excessive port pressure brought on by the kind of powder that was used in the load in question.

    Powders have different pressure curves and the powder in that round looks like it caused too much pressure to pass through the gas tube which forced the carrier to begin rearward travel while the empty case was still expanded and pressing against the sides of the chamber (i.e., “obturated”). As the carrier moved back and the bolt began to rotate, the cartridge was still held rigidly in place by pressure. The rotating bolt, particularly the ejector and the extractor, deformed the very hot and malleable brass of the stuck cartridge. Ultimately, the excessive pressure had nowhere to go but through the primer pocket, causing the primer to drop.

    So while the symptoms scream “overpressure,” the problem is really a matter of improper timing. AR10s are famous for this kind of problem. The same ammunition in a different rifle, i.e., a bolt gun, or an AR with a longer gas system, might function just fine. The length and size of the gas tube, the size of the gas port, and the distance between the port and the chamber all play into the timing equation.

    If this is a factory load, then I would avoid using it again in your AR10. If it's a handload, you need to switch powders.

    This is exactly why I don't get into reloading. The learning curve is steep and I don't have the time to learn everything about it.

    From what I understand, if you really want consistency, you would need to maintain a standard with brass, primers, powder, etc. All of these can vary in performance and cause issues.

    I suspect this is the reason Clandestine has a process for troubleshooting that includes factory ammunition.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    Am I seeing galling on the supportive lug edges on the bolt? I am also not seeing a bevel on the leading supportive lug edges. Do AR10 bolts not have bevels on the leading edges of the lugs? Or is it just not clear in the pic(and the pics look pretty dang clear to me)? :shrug:
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    You got me to thinking so, just for grins I pulled a sampling of my handloads and checked. All good. Whew! But I think I'm going to put this step into my SOP anyhow.

    Thanks

    Like I said, 4-5 out of a thousand. It's a good habit to get into. Depending on how I am loading, one at a time on my Rockchucker or continuously on my Dillon, every round drops into a case gauge before it goes into service.
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    Am I seeing galling on the supportive lug edges on the bolt? I am also not seeing a bevel on the leading supportive lug edges. Do AR10 bolts not have bevels on the leading edges of the lugs? Or is it just not clear in the pic(and the pics look pretty dang clear to me)? :shrug:

    Yes, you do see what looks like galling on the lugs, especially on the ones either side of the extractor. Possibly a result of beating the BCG out of battery?

    Can't say about bevels being standard.

    I'm going to replace the bolt. Any recommendations? A Tubbs spring is already on order.

    Thanks
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    If the bolt lugs were engaged at all and the bolt stayed closed, any out-of-battery condition would have had to have been extremely small. Equal to or less than the lead-in slope on the lug faces. If the lugs were only partly engaged prior to/upon ignition, I would expect to see some compression and/or chipping of the back corners of the bolt's locking lugs.

    OP - how do the back of the bolt lugs look?

    Just realized I didn't answer this question. Outrider58 noticed possible galling on the lugs so I took a closer look. There are some concerning wear marks, but could that have been from me beating the BCG out of battery? I did have to hammer on it more than I was comfortable with. But I have no frame of reference in that matter.
     

    clandestine

    AR-15 Savant
    Oct 13, 2008
    37,031
    Elkton, MD
    The back of the lugs on the bolt are not the only variable. The barrel extension can get damaged too. I have a few class examples of rounded barrel extensions.

    You'll need a bore scope to check them.

    Also check the gas key bolts. High amounts of vented pressure can lift the gas key and cause the has key bolts to fracture or break.
     

    DavidA

    The Master of Disaster
    Dec 6, 2013
    371
    Annapolis
    I had a similar problem. I was doing a ladder of 225 gr HPBT with RL17. COAL was 2.848, Any hoot I was running a ladder 44 to 48 gr A person in a bolt was getting 2500 FPS out of a 20.5 barrel. Any hoot no warning at 46.5 a round blew a primer. The blown primer was in the bolt face and after it started to return it’s cycle it pinged it back into chamber and as the next round was carried forward by the BCG to go into battery the blown out primer jammed the round at the neck in the chamber. The bolt could not move. I tried to mortar, used a hammer to push bolt charging out broke the charging handle. Tried to push rod down bore and back it out. No joy had to go home and disassemble before I could get round out. No other pressure signs I figure I did not drive primer in far enough or loose primer pocket. Going to give it a whirl again I did get 2,450 out of a 20” BHW 1*11 barrel


    Sent from my iPhone using Tapatalk
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    The back of the lugs on the bolt are not the only variable. The barrel extension can get damaged too. I have a few class examples of rounded barrel extensions.

    You'll need a bore scope to check them.

    Also check the gas key bolts. High amounts of vented pressure can lift the gas key and cause the has key bolts to fracture or break.


    Gas key bolts look OK. The barrel extension inspection and, if necessary, replacement, is going to be a more involved deal.
     

    DavidA

    The Master of Disaster
    Dec 6, 2013
    371
    Annapolis
    Just listening in all this makes me think I should get an adjustable gas block in particular when I am loading heavies in my AR10 like the 225gr. Because the signs of over gassing are there. First I had to put a piece of felt on the shell deflector because it was hitting it so hard that the brass was getting beat in particular when I am getting close to max on bullets 178gr and plus bullets. In addition after I disassembled the rifle I just noticed how dirty the bolt and chamber were. I am getting a 260 Rem barrel for my other AR10 and I am thinking I will need to get an adjustable gas block for this as well. It is so helpful understanding just what is going on in there. As always I appreciate all the input I get here. Thanks everyone for all your input.


    Sent from my iPad using Tapatalk
     

    inkd

    Ultimate Member
    Aug 4, 2009
    7,512
    Ridge
    Gas key bolts look OK. The barrel extension inspection and, if necessary, replacement, is going to be a more involved deal.

    If your barrel extension is toast, you will most likely be looking at a new barrel.

    You would probably have better odds of winning the powerball than getting a new barrel extension to line up perfectly with the gas port.

    But, if there is a way to get it done, odds are, Chad knows how to do it.
     

    kalister1

    R.I.P.
    May 16, 2008
    4,814
    Pasadena Maryland
    I just read an article where the over pressure issue was thought to be due to a reloader who loaded Pistol rounds and did not get all the pistol powder out of the powder dispenser. Then when loading rifle rounds the pistol powder mixed with the rifle powder to create a duplex load.
    OP: do you load pistol too? Or maybe even different rifle powders getting mixed?
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    I just read an article where the over pressure issue was thought to be due to a reloader who loaded Pistol rounds and did not get all the pistol powder out of the powder dispenser. Then when loading rifle rounds the pistol powder mixed with the rifle powder to create a duplex load.
    OP: do you load pistol too? Or maybe even different rifle powders getting mixed?

    Nope. Straight Varget, all the time.
     

    DarrellA

    Jacksonian Independent
    Aug 20, 2013
    1,184
    MD
    If your barrel extension is toast, you will most likely be looking at a new barrel.

    You would probably have better odds of winning the powerball than getting a new barrel extension to line up perfectly with the gas port.

    But, if there is a way to get it done, odds are, Chad knows how to do it.

    Ah, yes. That is likely a bridge too far for me.
     

    Users who are viewing this thread

    Latest posts

    Forum statistics

    Threads
    274,925
    Messages
    7,259,308
    Members
    33,349
    Latest member
    christian04

    Latest threads

    Top Bottom