New 6.5 Grendel AR- FTF problems...help???

[Wannashootit]

Our just-built AR in 6.5 Grendel has a frequent feed problem. Seems to occur most frequently when feeding from the left side of the mag, but has occurred on the right side as well.

The round doesn't center on the bolt when pushed forward, and jams as shown in this picture. If I pull back on the charging handle slightly (just enough to relieve forward pressure), and then release the round self-aligns and slides easily into the chamber.

Alexander Arms mags, Hornady 123 A-Max's, bolt and barrel are AR Stoner.

First AR build and would appreciate any suggestions...Thanks.

 

[BOLTRIPPER]

Re: New 6.5 Grendel AR- FTF problems...help???

my thoughts are ..........


there is not enough lube on the bolt carrier.....they should drip with lube......try it and report back.....its a simple fix to a simple problem

 

[animalmother85]

Re: New 6.5 Grendel AR- FTF problems...help???

Are you using an M4 upper receiver? I know that AR-stoner barrels come with barrel extensions that don't have M4 feedramps. That could contribute to your problem, but I'm still a little unsure as to why your rounds are not sitting where it should be in relation to the bolt face. Have you tried some other make magazines? I have some C-product magazines that I haven't had issues with, you could try them.

 

[Scottmilk9]

Re: New 6.5 Grendel AR- FTF problems...help???

Try a different mag first!

 

[bengates]

Re: New 6.5 Grendel AR- FTF problems...help???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">my thoughts are ..........


there is not enough lube on the bolt carrier.....they should drip with lube......try it and report back.....its a simple fix to a simple problem</div></div>

Um, only lube appropriately. There's no reason to "drip" lube on the BCG because only a few small areas contact the upper.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Scottmilk9</div><div class="ubbcode-body">Try a different mag first!</div></div>

This gets my vote.

 

[kvwpwr]

Re: New 6.5 Grendel AR- FTF problems...help???

sounds like it could be a mag problem, which kind are you using?

 

[STI_1911_Guy]

Re: New 6.5 Grendel AR- FTF problems...help???

Lube does help but i dont think it has anything to do with your problem. If it wasnt going all the way into battery or fully ejecting then maybe but not centering i dont think so. I would lean more towards possibly a feed ramp issue on the left side. Make sure everything looks right there and then start eliminating easy issues such as a mag, ammo. Then i would setup a camera and slowly work the charing handle forward and load a round and then go back and watch the video and see where the round starts to go off track and attack the situation from there. let us know what u find as u eliminate problems and see if we can help.

 

[lethal93ta]

Re: New 6.5 Grendel AR- FTF problems...help???

mine got stuck the same way, Im running C product mags in my 6.5 but I had to bend the front tabs up just ever so slightly to get them to feed right.

 

[msalm]

Re: New 6.5 Grendel AR- FTF problems...help???

It looks to me like the brass is tilted enough to the right side that the off-side rim is catching on the side of the ejector and not allowing the round to 'slide' left across the bolt face. You could probably either shorten the face of the ejector as they don't have to be flush with the bolt face to operate properly, or add a slight chamfer to the it on that side that might allow it to slip over. That's just from looking at the picture and it makes sense as if you pull back a bit on the charging handle the round will lay down in the center and then feed. I bet you have marks on the inside edge of your ejector. It could take a bit of touch-up to your extractor too. Some Grendel bolts come with a standard .223 extractor and they DO NOT work worth a shit unless reworked to a larger radius.

 

[Rootshot]

Re: New 6.5 Grendel AR- FTF problems...help???

I had the same problem. The solution is to take out the ejector, shorten it a "tad" (I know.... very scientific) and reassemble. The over-long ejector is keeping the case head from sliding into the bolt face. And causing it to wedge when feeding.

--Rootshot

 

[Rootshot]

Re: New 6.5 Grendel AR- FTF problems...help???

I had the same problem. The solution is to take out the ejector, shorten it a "tad" (I know.... very scientific) and reassemble. The over-long ejector is keeping the case head from sliding into the bolt face. And causing it to wedge when feeding.

--Rootshot

 

[Wannashootit]

Re: New 6.5 Grendel AR- FTF problems...help???

Puzzling.
I'm going to call A.A. tomorrow and see if I can get some insight.
Online searches have yielded some conflicting info- some say there's issues with the Hornady A-Max ammo, some say mag problems...

The bullets are getting scratched from the feed ramps (don't know if that's normal), and I can feel a distinct dent in the side of the case where it hangs up-I believe- right at the barrel extension/barrel connection (definitely not normal).

Again- first AR, so no experience here. I will add that while I would expect there to be some "force" required to strip the round from the mag, once that's done the round still requires a lot of force to get it over the feed ramps- it doesn't just slide up in there. Should it?

No obvious defects (burrs, etc.) on the feed ramps, very sharp edges, tho. Might it help to "ease" these edges on the feed ramps? I'm wondering if they're contributing to the hanging up.

 

[Wannashootit]

Re: New 6.5 Grendel AR- FTF problems...help???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Rootshot</div><div class="ubbcode-body">I had the same problem. The solution is to take out the ejector, shorten it a "tad" (I know.... very scientific) and reassemble. The over-long ejector is keeping the case head from sliding into the bolt face. And causing it to wedge when feeding.

--Rootshot </div></div>

Rootshot-

Thanks- you posted the same time I did, didn't see it till now.
You nailed it- the ejector is about .01 too long- it's past the rim of the boltface, and I can see how that might be the problem. We've taken it out, ground .015 off it so it's just below flush.

I did call A.A. today- and the tech suggested that the sharp edges on the feed ramp might also be the problem, and to check the alignment of the upper receiver feed ramp to the barrel extension ramps- they need to be tits.

They (A.A.) tumble their barrel extensions before assembly to get rid of any burrs and these sharp edges- a good idea. If shortening the ejector doesn't solve the problem, I'm going to take a Cratex wheel to the feed ramps to ease the sharp edges...

Thanks again.

 

[Rootshot]

Re: New 6.5 Grendel AR- FTF problems...help???

Wannashootit,

I can almost guarantee you it was the ejector. I have an identical picture to your's that I used to help diagnose my problem.

I tried all kinds of magazine mods, having M4 feedramps cut into the barrel extension / receiver, polishing the entry into the chamber, sizing cartridges more, applying dry lube to rounds, etc.

I wasted an inordinate amount of time and money diagnosing this and was very disappointed that the builder of my semi-custom rifle didn't catch this during the manufacturing process nor when I returned it (and they cut M4 ramps).

My guess is that the bolt face depth of the Grendel bolt makes it more sensitive to ejector length variations than on .556 rifles. I haven't measured it, but I would guess that distance from the face of the bolt to the front of the lugs is less than a .556 bolt.

--Rootshot

 

[Wannashootit]

Re: New 6.5 Grendel AR- FTF problems...help???

Rootshot,
Dead on.
My son didn't want to wait for me to pick up some cratex wheels today, and since we thought you had the problem nailed, he went ahead and re-assembled the rifle last night.

Not a single FTF anymore. Problem solved.
Thanks for saving me a TON of trial and error "fixes" that wouldn't have helped. I never would have even thought to look at the ejector...

 

[branson1369]

Re: New 6.5 Grendel AR- FTF problems...help???

Glad to hear you guys got it running with no FTF!!!

 

[Wannashootit]

Re: New 6.5 Grendel AR- FTF problems...help???

Huh?