Troubleshooting JP Enterprises AR10 - BCG Out of Battery

Breach_and_Clear

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So I have JP build that I recently acquired. It was built by a Marine Sniper Instructor so I know great time and effort was put into it. I am admitting I'm a little out-classed when operating this thing. Semi-auto precision platforms are new to me, and that includes using an adjustable gas block system.

I have read the instructions on tuning the adjustable gas blocks and being as the rifle is for LE competition use, it was recommended to have it in the "full-open" position to ensure reliability with various types of ammo. How far out exactly is the "full-open" position? I have a JP Enterprises JPGS-9D or 10D on my weapon. I am sorry if I don't know the exact model of gas block. I have the weapon operating somewhat reliably with 3 types of ammunition, but I want to ensure that I don't have the adjustment screw backed out too far. I am aware that migration is almost non-existent, but I still want to ensure that everything is installed correctly. The screw is much further out than I have seen on other rifles.

I did the tuning method starting with it closed and working back. The rounds eject and the weapon cycles, but I kept running into issues where the BCG wouldn't seat appropriately and I had to use the forward assist. The bolt was somewhat dry so I will clean it and try again to get an appropriate setting. I don't know if I should chalk that up to the gas block or another issue.

Thank you for your time.

(I have used the search function but couldn't find an answer. So I apologize if this is somehow a duplicate post.)


 
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Desert_Racer

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Are you shooting suppressed? The chamber can get really dirty and cause this issue if not cleaned frequently, in my experience. I’ve also gotten dirt in the barrel extension before, which caused similar issues.

Pull the BCG out and see if the bolt feels like it’s binding up in the carrier. Maybe there’s a lot of carbon buildup?

What buffer spring are you using? If you have a weak spring, this could be a cause as well.
 

Breach_and_Clear

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I am not running it suppressed. But upon further inspection, the chamber is dirty and pretty dry. This malfunction would only occur occasionally. I have a JP Silent Capture Spring and Low Mass BCG.

Any thoughts on the gas block as well?
 

Desert_Racer

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The only thing I could think of concerning your adjustment screw being backed out all the way (and I'm assuming not being overgassed) is that you have the heaviest spring installed on your SCS, and it may not be necessary unsuppressed. I believe the heaviest spring is painted red on one end and blue on the other. Where is your brass ejecting at in terms of clock position? To be honest with you, if you can work out the BCG not going into full battery issue, the rifle locks back on empty with the ammo you plan on using, and it ejects somewhere between the 2:30 and 3 o'clock, I'd leave it alone.

As for your chamber, clean it out and leave it dry. Someone can chime in if I'm wrong, but too much oil in the chamber can stretch it out over time firing it that way (remember that oil doesn't compress).
 

padom

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  • Mar 13, 2013
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    First off, clean the carrier, bolt and chamber and lube that BCG. Then close the gas all the way then open up 1 turn and try shooting 3 rd in the mag. Open the gas port block up 1 click at a time until it ejects brass, feeds loaded round and locks back on empty mag. Once you have it doing that fire 15rd in a mag and make sure it feeds 100% and locks back on empty mag. You may find you need to open the gas block up one more click during this final test.

    if that doesn't solve your issue then you have something else going on. Gas block not properly aligned or a buffer weight/spring issue.
     

    Breach_and_Clear

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    Ok range update.

    I did a detailed cleaning of the entire weapon earlier today. The gun had some carbon fouling but nothing significant. I cleaned it and lubed it properly. The BCG is super smooth and in great condition. Almost no wear.

    I also spoke with a JP rep in regards to the gas block. It is in the full open position now.

    I went to the range with 4 types of ammunition I had available. Ruag Tactical 163, Ruag Styx 167, Federal BTHP 168, and some standard 7.62 ball ammo.

    The gun fired fine. Held zero, ejected casings at the 2-3 oclock position. However I had the same failure to go into battery issue. I loaded standard 20 round PMAGS with only 3 rounds of ammunition each to make sure that it wasn't a magazine issue of some sort. I would fire one or two rounds and then have the BCG stop about 1/4 inch out of battery. It was enough that the firing pin was able to fall, but it wasn't close enough to impact the primer. The extractor also catches the round fine and is able to extract it without issue. If I tap on the forward assist, the bolt slides forward with just a tiny bit of pressure. I am including pictures of the spacing I am referring to.

    I cannot recreate this malfunction on an empty chamber. If I inch the bolt closed it still closes accordingly. When I use the bolt release on a live round, sometimes the malfunction occurs. When I pull the bolt back using the charging handle and really let it slide home, I don't have the issue.

    My components list is as follows:

    JP PSC12 Upper with dual charging system
    POF lower
    Bartlein Barrel 1:9.5 - 18 inches
    JP Low Mass BCG
    JP compensator
    JP adjustable gas block
    JP Silent Captured Spring

    So what could the potential issue be? Is the spring not strong enough to send the BCG home? Is the BCG too light? I am really new to the precision semi-auto platforms. Most of my experience is around bolt guns and mil-spec carbines. So I apologize if any terminology gets jarbled.




    out of battery



    closed with use of forward assist

    Guys any help would be appreciated. Thank you.
     

    Niles Coyote

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  • Aug 13, 2007
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    Pull the rear action pin and make sure nothing is binding as you slide the bcg back and forth. That done look at the jp scs assembly as it sits in the buffer tube. Are the scs and bcg in contact with each other when you close the upper back down on the lower? Sometimes you need to remove the spring retainer if the bcg and scs are not in contact. Finely, have you tried a different brand of mag, might be the the bcg is slightly contacting the mag and when it's feeding with the additional drag from the cartridge, losing velocity. If all that checks out I'd start looking at playing with spring weights and trying out a different carrier.

    I've got a grendel that was suffering similar feeding lag, acting like it was under gassed even with high pressure loads and "I think" I've narrowed it down to both my low mass and full mass jp carriers. I say I think, because I still need to rule out the bolt first but when I swapped out my jp bcg for a different non jp bcg the problem went away and I needed to close my adustable gas block from full open to nearly full closed.
     

    Breach_and_Clear

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    So one of the issues I'm noticing is that there is a considerable amount of wiggle room on the SCS assembly. The SCS defintely contacts the BCG when assembled, but the SCS moves back and forth about 1/4 of an inch. It is not compressed tightly as a standard buffer and spring would be. I understand that the retaining pin is unnecessary in regards to holding the SCS, but it still seems loose inside its own compartment. I understand that there are spacers available? Could this be the culprit?


    EDIT: I watched a few videos on youtube and specifically one by JP Enterprises. They said there should be no wiggle and that the SCS shouldn't make any noise. They said a simple fix was to place a quarter in the buffer tube to make up the additional width. I placed one quarter in the tube and low and behold the wiggle is gone and the spring tension is nice and tight on the retaining pin. (My SCS requires retaining pin after all.) I assembled the weapon with ease and there were no tolerance issues with closing it. So far it seems to have made a huge difference. I will take it to the range and see what I can find out.
     
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    Breach_and_Clear

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    Range Day 3 update. Still malfunctioning
    I have had this malfunction over the last 3 days for a total of 102 rounds fired of various brands of ammunition.

    If I were to swap out parts to maximize reliability, as this will be a law enforcement competition weapon, where would I start. I do not plan on running it suppressed. So should I keep the LMOS? Should I upgrade to a different SCS? Or is an SCS not necessary at all. Should I just revert back to a standard AR10 buffer and spring system?
     

    brcook03

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    Have you tried contacting JP directly and have them help you troubleshoot your build (specifically the malfunctions)? I saw where you said that you talked to them about the gas block.

    Their customer service is really quite good.
     

    Breach_and_Clear

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    So I have been in contact with JP and they are very helpful. Its just been through email correspondence so its taking a day or two here and there. And its always beneficial to think outside the box and get advice from various backgrounds like you guys.

    I ended up swapping out the SCS for a standard 308 carbine buffer and spring today. I fired multiple rounds without issue. Way better reliability but still ran into some issues.

    I would have the BCG close into the chamber appropriately, the hammer would fall, but the firing pin would not impact the primer. I had no mark on the casing other than the light dimple caused by the floating firing pin. So obviously the firing pin is able to contact the casing. I can also extract a live round from the chamber with ease. So I'm not sure if its a headspace issue.

    I have the JP EZ Trigger installed right now but its currently using the competition strength springs. The manual states that for LE and Military use that the more powerful spring should be used. So I am going to swap that out and see if it can help.

    I also spoke with the original builder of the rifle and he states that it is a brand new gas block and gas tube so its possible that the alignment or clearance of the tube is off slightly. I'll check for wear and see if thats the case.

    I am just chasing around an issue and I know the fix is there and probably a simple fix.

    EDIT: Another concern that was presented to me by a tech at JP was that it is possibly "bolt bounce." The LMOS slamming home too fast and bouncing slightly out of battery for the next round. I have heard of this occurring in full auto fireat times, but not with a semi platform in slow fire. So if thats the case, maybe I can turn the gas down or get a heavier buffer. Im not sure.

     
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    Niles Coyote

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  • Aug 13, 2007
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    I experienced bolt bounce with my AR Creedmoor, but there I was using a Full Mass carrier. It wasnt a consistent issue, but would happen about once every 5 to 10 rounds. It was difficult to track down as the hammer strike would be enough to close the carrier most times. I switched to the low mass but went with the highest power spring in jp's scs spring pack and the issue went away.

    Also, my gas was turned down already when that was occuring.
     

    bigjake83

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  • May 19, 2013
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    So I have been in contact with JP and they are very helpful. Its just been through email correspondence so its taking a day or two here and there. And its always beneficial to think outside the box and get advice from various backgrounds like you guys.

    I ended up swapping out the SCS for a standard 308 carbine buffer and spring today. I fired multiple rounds without issue. Way better reliability but still ran into some issues.

    I would have the BCG close into the chamber appropriately, the hammer would fall, but the firing pin would not impact the primer. I had no mark on the casing other than the light dimple caused by the floating firing pin. So obviously the firing pin is able to contact the casing. I can also extract a live round from the chamber with ease. So I'm not sure if its a headspace issue.

    I have the JP EZ Trigger installed right now but its currently using the competition strength springs. The manual states that for LE and Military use that the more powerful spring should be used. So I am going to swap that out and see if it can help.

    I also spoke with the original builder of the rifle and he states that it is a brand new gas block and gas tube so its possible that the alignment or clearance of the tube is off slightly. I'll check for wear and see if thats the case.

    I am just chasing around an issue and I know the fix is there and probably a simple fix.

    EDIT: Another concern that was presented to me by a tech at JP was that it is possibly "bolt bounce." The LMOS slamming home too fast and bouncing slightly out of battery for the next round. I have heard of this occurring in full auto fireat times, but not with a semi platform in slow fire. So if thats the case, maybe I can turn the gas down or get a heavier buffer. Im not sure.

    OP..

    I have seen this happen before, if you haven't already properly adjusted your GB it needs to be done, then call JP back and order a new spring for your SCS, you want the one that comes standard (BLK tip). The new spring will cost you like $5, do this and your troubles will be gone.
     

    Breach_and_Clear

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    So JP is allowing me to return my old SCS and is giving me credit towards a new one. So rather than switch out the spring on the SCS, I am just going to a newer Gen 2 model. They recommended the heavier style SCS that reduces bolt bounce. Additionally, like y'all have recommended, I should tune the gas block rather than run it in the open position.

    In addition to that I have replaced the hammer springs to the more reliable red ones. I checked the headspace and alignment of gas tube just in case. And I scraped carbon off every possible surface.

    Once the new SCS system arrives, I'll install that and tune the gas system appropriately. I believe its most likely a bolt bounce style issue due to the fact there are actual light primer strikes and that it appears the firing pin isnt striking at all. Additionally with the lack of physical obstructions in the chamber or the construction of the gun, it has to be something with the operating system.

    Thanks for all the replies and education. I'll get the hang of these semi platforms yet! ha.
     

    Mmfujita

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    Dec 23, 2017
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    Is it possible you might have one of the longer buffer tubes. Or vice versa? Or something along those lines?
     

    mtgale00

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    Bully on JP for stamping their name on someone else's problem. Just curious why you didn't put pressure on the Tier 1 builder for answers.
     

    Snuby642

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  • Feb 11, 2017
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    I guess thats why some le agency's won't let you run nonstandard stuff for patroll.
    Not even a trigger spring swap.
    And when you compete and win they strip your rig to check it.
    Some of the guys can just hear the difference.
    My son shot too good for thier liking and imidiatly had his riig stripped.
    Every piece of his rig had to meet the dept. Requirements.
    He just didn't like other people touching his shit.