More extraction issues

[nocoolname]

Here's some of the two I fired today. Factory loaded Hornady 123gr A-max. There's a scratch in the brass the length of it that I tried to get pictures of, but I think it's from the magazine lip and is easier to see than feel. I can't hang my fingernail in it, so I wouldn't think it would indicate something in the chamber.

[LRRPF52]

Do you have a lot of soot in your lower receiver in the Fire Control Group pocket?

Is there a lot of gas leakage around your gas block?

Do you have a spare bolt carrier? Try the gun with a different carrier, preferably a true Mil-spec M16 carrier.

What is the lug length on your bolt lugs, and what is the face depth on that bolt?

[SG4247]

The extractor needs a sharp corner underneath the lip, to grasp the rim. Yours appears to have a slight radius. A radius might allow the extractor to slip off the rim of the brass during firing. The square cut channel feature on a type 1 extractor, should look like the photo.
The position of your channel relative to the face of the bolt also looks very low.

The type one bolt I use with BHW barrels, has a very thin lip with a wide channel - based on the photo.

Notice this extractor is very different than yours.

Sorry my pics are poor, so much for the new I6S camera...

I really have heartburn with your extractor.

Who bolt is this?

[LRRPF52]

Good eye SG4247. Looks like someone tried to compensate with the inherent weakness in a short lipped extractor, by putting a radius on the groove and lip inner face.

[nocoolname]

Do you have a lot of soot in your lower receiver in the Fire Control Group pocket?

Is there a lot of gas leakage around your gas block?

Do you have a spare bolt carrier? Try the gun with a different carrier, preferably a true Mil-spec M16 carrier.

What is the lug length on your bolt lugs, and what is the face depth on that bolt?

No leakage around the gas block that I could see. As for the lower, it doesn't seem there's much soot in there, at least no more than any of my other ARs. I'll try it again this weekend with another carrier and report back.

My cheap calipers say the bolt lug length is 0.277" and face depth is 0.125"

The extractor needs a sharp corner underneath the lip, to grasp the rim. Yours appears to have a slight radius. A radius might allow the extractor to slip off the rim of the brass during firing. The square cut channel feature on a type 1 extractor, should look like the photo.
The position of your channel relative to the face of the bolt also looks very low.

The type one bolt I use with BHW barrels, has a very thin lip with a wide channel - based on the photo.

Notice this extractor is very different than yours.

Sorry my pics are poor, so much for the new I6S camera...

I really have heartburn with your extractor.

Who bolt is this?

I can definitely see the differences in our extractors. The bolt is from Underground Tactical, as I had read a few reviews saying they were GTG with the grendel. Who makes the best bolt for a type 1 chamber?

[SG4247]

I've had good luck with Olympic arms 7.62x39 bolt. Same as in my photos.

Out of stock currently, but due in any day:

http://www.midwayusa.com/product/798650/olympic-arms-bolt-assembly-ar-15-762x39mm-matte

One fellow in the club has 3000 rounds on this same bolt/extractor in his early Grendel using a compressed load of N540 and the 107 Sierra MK!

I keep thinking his bolt will crater any day, but never does.

[koden]

IMO looking at your fired brass your chamber may be a little rough. It will smooth out over time. That combined with the rounded edge on your extractor is causing your issues. I had an extractor like that and took a dremel to it and squared off the radius and my FTE issues went away. I then replaced the extractor with a quality one (cant remember where I got it though, probably my lgs). Replace your extractor and you will probably be fine.

[LRRPF52]

The best bolt with a .125" face depth is the LMT enhanced, hands down. It's made from an AerMet alloy, and guys who have broken every 7.62x39 aftermarket bolt out there have not been able to break the LMT. One guy who is renowned for breaking everything 7.62x39 in full auto mag dumps, was able to break the extractor lip off, which is the most common failure point on aftermarket 7.62x39 bolts, followed by lug shear.

7.62x39 has a lot of bolt thrust, because of the extreme case taper, so it can be really hard on bolts, even with significantly lower working pressure than 5.56 NATO.

[nocoolname]

Ended up getting an Olympic Arms bolt from Midway that came in today. I noticed a big difference in the extractor as it looks like SG4247's extractor. I didn't remove the extractor from the bolt assembly but noticed that it is also a lot stiffer than the Underground Tactical bolt I was running. I'm thinking that may have been part of the issue as well. I'll know by this weekend if my problem is solved though.

Thanks again everyone for the help.

[VASCAR2]

If the chamber is rough I'd consider polishing the chamber with Flitz. I do this on my 22 rimfire chambers and it really helps. I can't see it hurting anything on a centerfire chamber. I use a barrel mop with flitz attached to a cleaning rod. I attach the rod to a electric variable speed drill and am careful not to get into the rifling. A 20 gauge shot gun mop or 30 caliber mop might work pretty good on a 6.5 Grendel chamber.

[OldHorse]

So what was the verdict with the new bolt? I am having a similar issue with a BHW 20" barrel/bolt and am pretty sure is extractor issue. Been through most of the checks outlined in thread so was curious if your new bolt/extractor resolved problem for you.

[nocoolname]

Shot 20 rounds saturday with the new bolt and didn't have any issues at all. This seemed to have fixed the problem.