Ar-10 in 6.5CR Feeding Problem-Need Help

[Jeff361]

I have built a DPMS patern side charging AR-10 in 6.5 creedmoor with top quality parts and cannot get it to function correctly.... reaching out to the forum for advice. The build is on a matched Gibbz G10 side charging upper/lower receiver. Operating system and barrel are all JP Enterprises. Trigger is Geissle SD-E 2 stage trigger. DiamondHead Handguard. Luth-Ar stock. I have tried Magpul and Lancer magazines.

I have worked through all of the function issues... gas system, bolt hold back, barrel contact with handguard issues etc.

I continue to have a problem whereby rounds will not feed smoothly onto the feed ramps of the JP barrel extension. A few rounds will feed and then either one from the left or one from the right side will nose dive directly into the flat spot that is between the top of the magazine and the bottom edge of the feed ramps. Essentially the cartridge gets wedged between the bold face and the barrel extension. Like any AR platform the magazines wiggle a bit and move up a and down slightly..... this is just enough to cause the feeding issues.

I am not sure if the feed ramps milled into the barrel extension are machined incorrectly, or is the lower receiver out of spec and causing the magazines to sit too low, or is the upper receiver milled a bit off and not seating the barrel in the right location to allow the feed ramps to meet up with the magazine at the right height.

Check out the attached photos and let me know your thoughts on how to fix this issue. I have a couple of thousand $$ into this rifle and its driving me crazy getting it to function.

Thanks
Jeff361

 

[bigjake83]

We need to see some more pictures of the upper receiver with no mag inserted. It could just be a magazine compatibility issue, or your feed ramps may need to be worked on either way it should be a easy fix, you should try picking up a lancer Mag or another quality .308 AR Mag.

You should also Copy and Paste this same write up/question to Gibbs and see what further actions they recommend. it also States on their website that you have to use their proprietary Cam Pin to get proper operation.

 

[GUNNER10]

Has your rifle ever functioned correctly?

Something to be aware of is that most of the parts that you used in your build were built to a certain commercial spec and while the parts you selected may be high quality, they may not interface well due to tolerance stacking. Its hard to say exactly what it might be.

All manufactures of mags feed ever so slightly differently, what mags were the gibbs receiver set designed with in mind? Same thing with the Barrel, that barrel was engineered for use in the JP upper, what mags did they have in mind when on making their receivers.

It may prove less frustrating to possible pick up a JP receiver set, or quite possibly part your rifle out and pick up a factory gun.

you can find some pretty nice guns in that price range, Daniel Defense, LMT, POF, Larue. All of pretty good track records for performing right out of the door,

There is nothing wrong with doing a build but one has to realize that all of the parts may or may not play together nicely

 

[Jeff361]

Guys... thanks for the replies. The rifle has not functioned correctly from the beginning. I had a few other compatibility issue that have been solved...IE... DiamondHead handgaurd ID to small for JP Heavy Contour barrel, gas block issues etc.

I am using the proprietary CAM pin.... I have ar15's built on side charing GIBBZ receivers that function flawlessly.

Here are some detail images of the barrel extension and feedramps.

I have also sent the details to Gibbz and JP.

Further advice is much appreciated.

I am using both lancer and magpul mags.... have tested 8 magazines and the

feeding issue occurs with all of them.

 

[Mike_in_FL]

You can try using a metal magazine like an ASC and getting the Badger Ordnance feed lip tool to adjust the front of the mag to hold the cartridges at a more upward angle rather than as level as these look.

When you describe where the bullet is striking, do you mean the flat edge of the barrel extension between the ramps? After buying a used barrel that someone "worked on" the feedramps, don't. If it seems like that's the problem, send it back to JP.

If you make the opening any wider .26 caliber bullets will go right between them and hit the back of the barrel on the side of the chamber. The cartridge will not move up until the neck/shoulder junction of the case hits the ramp and then it's too late to feed into the chamber unless bullets are seated super short.

 

[padom]

Ive built more custom 6.5cm AR's then I can count with custom barrels using JP barrel extensions. Never had an issue. Your barrel extension looks just fine. Run the bolt and when it fails/jams get us a picture of that jam.

 

[padom]

Also, Ive never used either of those mags. ASC SS, Larue, and KAC are all I use and run flawless and have way longer COAL's than those 2 mags.

 

[padom]

Building large frame gassers is completely different than AR15's. There is no standard like AR15's. Regardless if your Gibbz AR15's run great, that means nothing when you play in the large frame gasser world.

We need to see whats happening when you say it wont "function correctly." Pictures speak 1000 words. Lets see them. And please get us some real pictures inside that upper with the mag inserted with rounds in the mag and with rounds out of the mag. Those tiny, low quality pictures are hard to see whats going on.

Here's some pics of my 6.5cm gasser. MEGA Receiver set with JP barrel extension and KAC SR25 mags.


6.5cm rounds sitting in mag












Pulled the charging handle back to release the bolt stop and slowly starting to let it go forward

 

[bigjake83]

Guys... thanks for the replies. The rifle has not functioned correctly from the beginning. I had a few other compatibility issue that have been solved...IE... DiamondHead handgaurd ID to small for JP Heavy Contour barrel, gas block issues etc.

I am using the proprietary CAM pin.... I have ar15's built on side charing GIBBZ receivers that function flawlessly.

Here are some detail images of the barrel extension and feedramps.

I have also sent the details to Gibbz and JP.

Further advice is much appreciated.

I am using both lancer and magpul mags.... have tested 8 magazines and theView attachment 7133029 feeding issue occurs with all of them.

It's difficult to see because your chamber is so damn dirty (that in itself is not helping as well) and your pictures are small but it appears your upper receiver has no feed ramps, in the picture below I have indicated from Padoms pics where you need to blend your upper receiver feed ramps with the feed ramps of the barrel extension. It is extremely easy to do with the right bits in a Dremel.

Again also order some quality mags from the ones that have been mentioned above by other members.

 

[stevieb92]

Magpul Pmags have worked flawlessly for me in my 3 LR-308 builds (1 - .308 Win and 2 6.5 CM). Two of those are built using Mega receiver sets and one was built using an Aero Precision receiver set. All three use Ballistic Advantage barrels. I've never experienced an issue with the Pmags in any of mine. I have no experience with Lancer mags.

 

[Jeff361]

Thanks for all of the feedback...... I will take some higher res photos with some better lighting. Will also pick up some steel mags and try those to see if they work. Maybe just a little filing and polishing of the junction between the upper and the feed ramps will fix the issue.

 

[TampaBud]

CP Defense is making a 10rnd SS mag for 308 and 6.5. I've had a lot of success with those and PMAG. If you want to test the CPD mag, direct message me and I'll send it up(assuming you're north of Florida) for you to try.

 

[Jeff361]

TampaBud.... thanks for the info. I just picked up a few ASC steel magazines... they look similar to the CP mags. I have not tested them yet... but they fit tighter in my magwell and also appear to present the bullet at a better angle than the PMAGS and Lancers that are giving me issues. I have also filed and polished my feed ramps.... so hopefully with new metal mags and adjusted ramps my feeding issue will be fixed.

 

[TampaBud]

They do look similar but you’ll find some difference in manufacturing quality and finish. My mag is here if you want to try one from CPD- don’t mind popping it in a bubble envelope and sending it your way. Keep me in the loop.

 

[Jeff361]

Thanks.... I'll let you know.

 

[bfoosh006]

Are you firing reloads ?

And if so, what OAL ?

You might try seating them a little deeper. Just a thought.

If it was mine...I would dremel polish the feed ramps down into the RE. Done prudently it should greatly help feeding.

Judging from your pics... it shouldn't take much.

 

[Tapper]

Also, what bullets are those? I've had issues with long secant hybrids, especially the 140g Berger.

But yeah, clean it first, then blend the feedramp, then try using a non-hybrid.

 

[Lawless]

I agree that the ramps should be blended into the lower receiver. It looks like there is an actual step between the barrel extension and the receiver that is catching the nose of the cartridge.

 

[Jeff361]

I dislike this approach because aluminum is far less tough than aluminum with anodizing...but you could use a cratex wheel on that junction there to blend the interface with the upper. Then clean it like crazy. Also, can you please post a picture of your magazine catch on the non-ejection port side of your lower?

I find most issues with mags are caused by incorrect placement of the cutout for the mag catch..

Finally, you may also have gas system overpressure issues causing excessive bolt carrier velocity. Tune your gas system so that it is a few clicks past locking back on a magazine when fired single shot.

It is ONE of these issues:

Mag catch doesn't hold the magazine in the proper place due to the location in the lower of the cutout
Mag catch is out of spec and does not position the magazine properly.
Lower too tall from the deck to the center of the upper mounting pins.
Bore in the upper is too high versus the location of the pin holes.
Magazine is out of spec.
Magazine well is too far back or forward in the lower.
Receiver extension has rough edges that could be polished.
Bolt velocity too high causing nose dive.
Bolt velocity too low.

Thanks for the feedback.... I have been testing my rifle with factory ammo..... . Had the upper/barrel extension blended and polished by my gunsmith.... tested... and still having the same issue. Also adjusted gas per JP instructions and determined that it is not a gas issue. It appears to be related to the presentation of the magazine.... have tested multiple Pmags, Lancers and ASC.... Have now spoken to Gibbz.... rifle has been sent off to them to see if the upper and or lower were milled out of spec.

 

[Darqusoull13]

To echo what @padom previously said, building a Large Frame (AR-10) rifle is NOT the same as building Small Frame (AR-15) rifle. Parts are not always compatible and you need to know what you are doing. My 6.5's and 308's all function with factory ammo as well as my reloads but when folks are function testing / trouble shooting I ALWAYS recommend starting with quality factory ammo to rule out issues with loads.

@Jeff361 once you get your rifle back let us know what they said.

 

[Jeff361]

Rifle was shipped off to Gibbz Arms for testing. They ran Sellior&Bellot and Winchester ammo through with zero issues from all of my magazines. I then sent them Hornady American Gunner and some of my handloads ( Hornady Brass with Berger 130 OTM loaded to magazine length) and they experienced the feeding problems. They then changed out my JP BCG to a DPMS BCG and did not have any feeding issues with the Hornady or my handloads. They diagnosed the issue to the steepness of the bottom part of thre BCG... see photo. They said that on the Hornady and handloads, the angled edge was picking up the round below the top round and pushing it forward just enough to get the top round to wedge between the magazine feedlips and the front edge of the barrel extension. Rifle has been sent off to JP with same ammo for testing.

 

[Jeff361]

Here is the photo of the 2 BCG... JP on the left and DPMS on the right

 

[Lawless]

Well, it shows that pretty much any big AR will need tweaks.

I hope they get it sorted out for you OP

 

[shibbycomm]

Im having this same exact issue, my Ar10 in 6.5 likes the winchester and sellior but acts up with the Hornady stuff. I am going to check to see if my bolt carrier looks more like the JP carrier on the bottom from your pictures. My bolt carrier is a ballistic advantage that was purchased through a group buy on the hide almost 2 years ago, which I believe is a relabled toolcraft (I could be mistaken, it has been awhile since my research). Yes, I still dont have it running perfect after 2 years, sad. I bought a new JP bolt for the BA carrier and while it did seem to help, it did not fix the feeding issues completly with the Hornady factory ammo. I am very interesting to see what JP says. Please post your findings.

 

[2aBaC̶a̶]

It looks like your barrel extension protrudes out past the edge of your upper creating a lip for bullets to hang up on? It doesnt take much to cause an issue.

How comfortable are you with a dremmel? It's a 5 minute fix.

Look at the pictures below. One is Padoms. You notice his feed ramps have a slight curve back from the edge of the upper. And yours clearly hang over with copper evidence that a bullet tip is catching.

I personally take my feed ramps into the reciever more like M4 style.

Blaming the JP BCG sounds like a cop out. And while a different one may function better it doesnt address the root issue. Same with different ammo. I would bet money the upper is short by a couple thousand where the barrel extension sits. If Gibbz couldn't figure this out it would be the end of our relationship.

 

[John_in_WYO]

This kind of post is why SH is one of the very first forums I read daily.
What a great bunch of guys to help each other out.
It taught me something as well.
Well done, gents!

 

[padom]

Blaming the JP BCG, one of the best out there is funny to say the least. I cant tell you how many large from 6.5cm gassers Ive built with both Aero M5 and MEGA receiver sets with JP and RCA complete BCG's. Never a single issue with any of them. Just putting that out there.

I can already see this thread having people question using JP BCG's. They shouldnt.

 

[2aBaC̶a̶]

Blaming the JP BCG, one of the best out there is funny to say the least. I cant tell you how many large from 6.5cm gassers Ive built with both Aero M5 and MEGA receiver sets with JP and RCA complete BCG's. Never a single issue with any of them. Just putting that out there.

I can already see this thread having people question using JP BCG's. They shouldnt.

Yeah, I call BS. I have Aero M5 with JP and they works flawless. I'm about to do another. Then again the Aero recievers have M4 feed ramps built in so...

PSA, If anyone wants to dump their JP BCG for something more reliable let me know.

 

[Jeff361]

Rifle just arrived at JP today..... I sent them ammo... I am sure that with their expertise they will diagnose the issue and come up with a solution. I own a lot of JP products and can attest that they are top quality. Lets see what they discover. Stay tuned.

 

[shibbycomm]

Any updates from JP?

 

[ufg8rmike]

Ya, don’t leave us hangin , soo many ppl start threads but never close em out with results/solutions

.

 

[Jeff361]

Any updates from JP?

Dave Cammack at JP still has my rifle, mags and ammo. I should have feedback after the holidays.

 

[quiksilv81]

Im having this same exact issue, my Ar10 in 6.5 likes the winchester and sellior but acts up with the Hornady stuff. I am going to check to see if my bolt carrier looks more like the JP carrier on the bottom from your pictures. My bolt carrier is a ballistic advantage that was purchased through a group buy on the hide almost 2 years ago, which I believe is a relabled toolcraft (I could be mistaken, it has been awhile since my research). Yes, I still dont have it running perfect after 2 years, sad. I bought a new JP bolt for the BA carrier and while it did seem to help, it did not fix the feeding issues completly with the Hornady factory ammo. I am very interesting to see what JP says. Please post your findings.

I had issues with my 6.5 Creedmoor build. Mine ended up being undergassed. My gunsmith opened it up and it runs great now. Just another thing for you guys to check

 

[stupkat]

Dave Cammack at JP still has my rifle, mags and ammo. I should have feedback after the holidays.

What did you find out on this? Ive got an AR build (6.5 grendel though) thats having the exact same issue. Itll feed crap Wolf ammo about 90% of the time but fails to feed my hornady black or federals rounds. Theyre slamming into the exact same spot and im on my 4th type of mag. Ive ordered a new upper to see if that solves the issue

 

[Jeff361]

I finally got my rifle back from JP in February. They machined a small feed ramp into my upper and polished the underside of the BCG. I have now begun to load test. This rifle does not like longer bullets. 130 Berger’s and 123 Scenars feed perfectly as long as they are seated below 2.80. Also discovers that ASC metal mags and Pmags work the best.... Lancers still have intermittent issues. Just tested Berger 130 with Varget in Hornady brass and seeing groups of .75 with 37.9-38.2gr.... velocity is 2671-2693. Also had tested the 130 with H4350 going 2750-2800.... but groups and SD were terrible.

 

[rpoL98]

I finally got my rifle back from JP in February. They machined a small feed ramp into my upper and polished the underside of the BCG. I have now begun to load test. ...

@Jeff361
pics of alluded-to "small" feed ramp? sorta like the AR-15 M4 feed ramps?