Ejecting and Feeding Problems

[alansarmory]

Hello All:

I am new to this forum and have run into an issue with my first 6.5 build. I am using a Mega Arms upper and lower with a Alexander Arms 20" barrel and bolt, Rock River bolt carrier, and Alexander Arms low profile gas block. My lower is also Mega Arms with a collapsible stock and a standard 5.56mm buffer and spring. I am also using an Alexander Arms 10 round magazine.

So on to the problem. Initially it would strip a round from the magazine, chamber it, and fire it with no problem. However it wouldn't fully eject the empty case, which would stovepipe in the ejection port. First thing I though was the gas block wasn't lined up and adjusted it. So what happened next was it would fully eject the case but the bolt wouldn't go back far enough to strip a new round from the magazine. After a few shots it then reverted back to my first issue (Stovepiping). Can't remember if I adjusted the gas block again but I don't think so. I also noticed that the bottom of the bolt carrier has brass streaks along it from the rounds in the magazine. I also noticed that the rounds in the magazine have a groove cut into them from the bolt carrier move over them. Not to deep but not something I've not noticed before with 5.56mm rounds (Maybe they were there but I just never noticed).

I think I've ruled out the gas block alignment. I also don't think there is an issue with the size of the gas hole in the barrel since it, the gas tube, and the gas block all came from Alexander Arms.

-Could the drag on the rounds be enough to prevent the carrier from going back fully?
-Could the 5.56mm bolt and spring be the issue?

I'm at a loss! Thanks in advance for any insight anyone could give me.

[DirectDrive]

1. Try single loading with an empty mag.
Does the bolt lock back on the empty mag ?
If yes, then the gas system is doing its job and you can focus on the mag.

2. Try a different magazine.
If a different mag is not available you could try short-loading your present mag, say with 8 rounds.

[davidj]

I have a complete AA upper and the same thing happens. It doesn't stovepipe but it will occasionally leave expended case in the chamber. It doesn't lock back on an empty mag unless it is done manually. It seems that the bolt is not coming back far enough to catch the cartridge and the feed problem occurs with both Hornady factory and reloads ( in all six mags).

[DirectDrive]

I have a complete AA upper and the same thing happens. It doesn't stovepipe but it will occasionally leave expended case in the chamber. It doesn't lock back on an empty mag unless it is done manually. It seems that the bolt is not coming back far enough to catch the cartridge and the feed problem occurs with both Hornady factory and reloads ( in all six mags).

Has this lower functioned normally with a different upper ?

[davidj]

It is an old SP-1 . It has functioned flawlessly in .223 mode (still does).
I should add this is a Bill Wylde build with a Kreiger Barrel so the .223 upper isn't really a SP-1 anymore.

[DirectDrive]

It is an old SP-1 . It has functioned flawlessly in .223 mode (still does).
I should add this is a Bill Wylde build with a Kreiger Barrel so the .223 upper isn't really a SP-1 anymore.

Well, sounds like something is up with that Grendel gas system.

Do you know what your gas port size is ?
http://www.65grendel.com/forum/showthrea...-port-size

Before doing anything with my gas port I would try a CAR buffer and the lightest carrier that I could find/borrow.

[davidj]

Talked to Jacob at AA today . I will be shipping the upper back in the AM. Hopefully they will be able to figure out what is causing the malfunction .

[warped]

That is the solution, if they built it they will take care of it, no need to worry.

[rkflorey]

Another possibility is that the gas key on the bolt carrier may be loose or leaking. If one of the cap screws is loose or broken it will appear normal and leak enough gas to cause the problems you are experiencing.

[davidj]

[ATTACH=CONFIG]371[/ATTACH]

Another possibility is that the gas key on the bolt carrier may be loose or leaking. If one of the cap screws is loose or broken it will appear normal and leak enough gas to cause the problems you are experiencing.

[attachment=275]
You hit it right on the head. My upper came back this AM. I am trying to attach note that came with it. I still cant get a bipod on it. I am off to the range to see how it works.
More to follow.

[LRRPF52]

Hello All:

I am new to this forum and have run into an issue with my first 6.5 build. I am using a Mega Arms upper and lower with a Alexander Arms 20" barrel and bolt, Rock River bolt carrier, and Alexander Arms low profile gas block. My lower is also Mega Arms with a collapsible stock and a standard 5.56mm buffer and spring. I am also using an Alexander Arms 10 round magazine.

These are the first potential problems I see. RRA BCG's use AR15 carriers-too light. A Standard carbine buffer is usually 2.9 oz., again too light. Use an M16 carrier and H2 or heavier buffer with the Grendel.

The brass streaks on the bottom of the bolt carrier are normal, as are the slight scratches on the cases.

The Grendel gas and 5.56 gas are different systems, with the Grendel pushing long, heavier bullets with less chamber pressure, while the 5.56 pushes short, very light bullets with very high chamber pressure. The Grendel needs a heavier buffer and standard M16 carrier for starters, although it can be tuned with certain loads with an adjustable gas block.

[LRRPF52]

[ATTACH=CONFIG]371[/ATTACH]grendel.jpg
You hit it right on the head. My upper came back this AM. I am trying to attach note that came with it. I still cant get a bipod on it. I am off to the range to see how it works.
More to follow.

This is why I prefer to unitize my bolt carriers and carrier keys myself, with a high-temp locking compound, on an M16-weight carrier. Black Loctite or other hardened metal epoxy resins for the screw threads and carrier key to bolt carrier body junction, with proper screw torque.

Also, the upper has only half of the equation for your entire system, leaving out the buffer and recoil spring, which could make or break you. Good thing AA found the loose carrier key.

[davidj]

[ATTACH=CONFIG]371[/ATTACH]grendel.jpg
You hit it right on the head. My upper came back this AM. I still cant get a bipod on it. I am off to the range to see how it works.
More to follow.

Well for the first time since I bought it the Grendel worked without any malfunctions. I used 123 Hornady AMAX factory ammo first time around. However my second shot resulted in a pierced primer. I am not sure what to think about that.

[warped]

Keep shooting, if it happens again take note of it.

There are various reasons this may have occurred