Trouble with JP Rifles AR build

G

GatorNeedsHisGat

Private
Minuteman
Apr 16, 2012
7
0
32
#1
Got a question for any AR-15 gurus out there.
I recently put together an AR-15 w/ 22" JP Enterprises barrel, JP modular handguard, Harris bi-pod, Larue Stealth upper, Leoupold 3.5-10x scope. I've put about 200 rds through it and haven't seen better than 5" groups at 100yds (used Hornady 5.56 75gr match and HPR .223 60gr).

I switched out the upper assembly with another 16" one, used the same scope, bi-pod, and lower assembly, and got much better groupings, around 1.5". Pretty sure the problem is with the upper because I did the installation myself.

If anyone has experience with JP barrel/handguards or had any advice for me about barrel installation I'd love to hear it.
 
#2
Re: Trouble with JP Rifles AR build

Did you torque the barrel with a torque wrench? You might try pulling it apart and reassembling it carefully ensuring you follow torque values.
 
#3
Re: Trouble with JP Rifles AR build

I've had many JP upper assemblies and JP barrel builds and never had one do worse than 3/4MOA with good ammo. I normally shoot 55gr v-max or 69gr SMK hand loads but all my JP's will hold 1" at 100yds with plain ol' cheap 55gr blastin' ammo.

Even if the barrel nut isn't torqued correctly it should do better than 5" groups unless it's just plain loose.

Can you post a pic or two of your build? Maybe that would help identify the problem.
 
#4
Re: Trouble with JP Rifles AR build

It sounds like there's a ghost in the machine somewhere, but the only way to know for sure where that might be is to strip the upper down completely and reassemble using the proper tools and torquing the barrel nut down properly within the specified range (which for that setup, I think JP recommends 50-80ft/lbs...they generally have their instructions available on their site if you don't have them or didn't use them when putting this upper together). Also, while you've got it all broken down, carefully inspect each component for any signs of unusual wear/tear, damage, etc., to ensure that it isn't a basic component problem, as well as cleaning up any leftover crud, loctite, etc. from the components.

Once you have it all reassembled, go at it again, but instead of the bipod, bag the rifle or find a rest to test it out. While it doesn't sound necessarily like a bipod/bounce/loading issue, it isn't beyond the realm of possible and its worth it to remove all variables that you can for testing purposes. While you are at it, let someone else whom you trust to be a competent shooter with an AR have a crack at it. You might also try a different ammo (although the stuff you were using is of good quality and even if your barrel doesn't like it all that much, should perform far better than 5MOA).

If you still can't get it to shoot with any of the above, then it may be time to get JP involved and see if there isn't a root problem with your barrel. Even JP can make mistakes and bad barrels happen. While you'd hope it would get caught upon inspection/testing, again...stuff happens.
 
#5
Re: Trouble with JP Rifles AR build

5" groups @ 100??? Post some pics of the upper. I would just send it in to JP and have them assemble it at this point. They charge $100 an hour and it would take them between 1-2 hours. JP barrels should do better than 1
 
#6
Re: Trouble with JP Rifles AR build

Not a AR15 but I assembled my LR-308 with JP Supermatch barrel, LMOS BCG, adjustable gas block. It is sub MOA at 100 yards, all I shoot are my handloads.

I didn't have barrel nut wrench so I hired dude to torque it. I watched him do so. In getting the nut assembly, and by the way it's a JD Machine free float hand guard which uses same style nut as JP, in getting nut tight and lined up with the gas tube hole in receiver, he torqued the living hell out of it. I asked how much torque, he said "I don't know". So I called JP one time for something brought up that story with one of the JP engineers. He said its all good and even 150lbs is ok and won't hurt anything. Sometimes, when the planets align, I can shoot holes that kiss each other from 100 using this fine stick. Sometimes I shoot some bullets and find only one hole, it happens sometimes.

Did you use their "Supermatch" barrel?

Good luck...
 
#8
Re: Trouble with JP Rifles AR build

[img:left]http://www.flickr.com/photos/91630831@N05/8322662421/in/photostream[/img] [img:left]http://www.flickr.com/photos/91630831@N05/8322660713/in/photostream[/img] [img:left]http://www.flickr.com/photos/91630831@N05/8323725784/in/photostream[/img]

Hopefully the photos made it. One thing i thought was weird was that when i press the hand guard and barrel together I can almost touch the gas block to the side of the hand guard. You can see the gas block screws in picture #2 are pushed all the way to one side (only the barrel moves not the hand guard).

I'm thinking I'll try reinstalling the hand guard with around 80 ft*lbs which is the upper value that JP gives in the instructions for the hand guard. If it still sucks I'll probably try to contact JP. However their website says that they aren't doing custom work because of the overload of orders.
 
#10
Re: Trouble with JP Rifles AR build

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GatorNeedsHisGat</div><div class="ubbcode-body">One thing i thought was weird was that when i press the hand guard and barrel together I can almost touch the gas block to the side of the hand guard. You can see the gas block screws in picture #2 are pushed all the way to one side (only the barrel moves not the hand guard).</div></div>

I took a look at your pics and I'm a confused a bit by a couple comments in your reply.

1 - Does the gas block actually touch the inside of the handguard (especially under the stress of loading your bipod)? If so, it may be time for a lower profile block to prevent you losing your free-floated barrel depending on your answer to #2 below.

2 - By the gas block being "pushed all the way to one side" do you mean that the barrel/block are not centered in the tube? If so, there was a problem with some JP/VTAC handguards a while back that were "warped" for lack of a better word that caused them to not be straight, causing issues (albeit not 5MOA issues).

3 - What do you mean "the barrel moves" in your post? If the barrel "moves" at all, you've got a recipe for miserable accuracy problems without question. If you can hold the rifle down firmly and move the barrel around, you definitely got problems!
wink.gif
 
#11
Re: Trouble with JP Rifles AR build

It looks like your barrel nut isn't centered on the gas tube hole cause the gas tube to be at an angle and the gas block being pushed to the side.

I'm surprised it cycles but I don't know why you're getting 5 inch groups.
 
#12
Re: Trouble with JP Rifles AR build

By moving the barrel I meant that I can wiggle the barrel from one side of the hand guard to the other with just a little bit of pressure. It doesn't seem loose, it just flexes about 1/2 inch in any direction. I haven't had this issue on any other AR but I'm not sure if it is an issue with longer barrel rifles (my other ones are 16" or shorter).

Thanks for the advice. I thought I had the barrel locked down pretty tight but I'm gonna try reinstalling it with around 90 ft*lbs and see if I can reduce that movement.
 
#13
Re: Trouble with JP Rifles AR build

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: GatorNeedsHisGat</div><div class="ubbcode-body">By moving the barrel I meant that I can wiggle the barrel from one side of the hand guard to the other with just a little bit of pressure. It doesn't seem loose, it just flexes about 1/2 inch in any direction. I haven't had this issue on any other AR but I'm not sure if it is an issue with longer barrel rifles (my other ones are 16" or shorter).

Thanks for the advice. I thought I had the barrel locked down pretty tight but I'm gonna try reinstalling it with around 90 ft*lbs and see if I can reduce that movement. </div></div>

Uh...NO!! That is NOT normal with any AR barrel regardless of length, contour, etc., etc. Any "movement" or "play" of the barrel like what you are describing is a serious problem well outside the norm and is exactly the sort of issue that will give you what would otherwise be thought to be impossibly bad accuracy with an AR (particularly one assembled with quality components like what you have described).

I would do the reinstall that everyone has recommended, but I'd suggest that you not exceed the upper limit on the torque range established by JP which should be not more than 80 ft/lbs. Any more than that and you risk doing more harm than good. If it won't properly tighten down and keep the barrel snug at the top end of that range, then applying more torque isn't likely to solve the problem which at that point likely rests elsewhere.
 
#14
Re: Trouble with JP Rifles AR build

Could the loctite seal on the receiver extension broken loose somehow? Not sure how unless it was just at the exact instant the barrel nut wrench let up. Did you clean and rough up the threads and let set up for 24 hours? Still don't know what else could be that bad if the barrel nut isn't loose.
 
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