7.62x39 converted to 6.5 Grendel not chambering

[CPC24]

I’ve just built an upper in 6.5 Grendel. I found some once fired 7.62x39, and resized it to 6.5 Grendel. The neck, base, and shoulder are correct, but it still won’t chamber. I’m using a Lee sizing die, and it touches the shellholder. What am I doing wrong?

[Echd]

You said the necks are sized right but are they too thick? The thickness of the neck can be as such to impede chambering. Anyone who has tried to cut down 223 to 300 knows this is a pain in the butt with certain headstamps (and a nonissue with others).

[Rcmaveric]

i had the same problem. Problem for me was the shoulder on the case. i had to polish a couple thousands off the shell holder. you could also polish it off the die base. Could be because the marketing and patton shinigans, flex on the press or bad die QA. Due to marketing shinanigans there are three different chamber types. Grendel, Grendel II, and .264 LSB. only difference is the shoulder angle. It has been a been several years since i did read the history lesson. Good read though. Smoke or sharpy a dumby round and look for the rub marks. From personal experience i am betting on not enough shoulder set back. only takes .003 ish to stop your bolt.

[CPC24]

I found some Grendel brass, and the dimensions are the same. It must be the shoulder. I got a couple 7.62s to chamber, and they fireformed. They chamber now. It’s a 6.5 Grendel Type 2 barrel and bolt. The extractor works even with the converted cases. I’ll try polishing the shellholder down.

[Rcmaveric]

This explains it all. About 3 posts down.

https://www.ar15.com/forums/ar-15/6_...h_/121-696465/

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[CPC24]

I polished the shellholder. There was a lot of slop between it and the ram. The shoulder is being pushed back more now, and it will chamber if I force it. It’s probably just a bad batch of brass. I found actual Grendel cases and they work perfectly.

[WehrmannsGeweher]

Why would anyone want to do this when Grendel cases are available ?

[Rcmaveric]

Why would anyone want to do this when Grendel cases are available ?

Grendel brass is expensive compared to 7.62×39. Plus i find 7.62×39 brass at my range sometimes. So those are free. Its not so much of a brass issues. Its head space issues caused by out of spec chambers and loose tolerance dies. Doesnt happen often, but does occur. Swiss chease affect if you are familiar with the term.

When it happened to me on a new grendel, it wasnt just grendel brass. It would do that on all my brass. Making sure the press was mounted sturdy helped some. Annealing the brass helped a bit also. Taking .003 off the shell holder really brought it into a more consistent chambering. My old Grendel had .264 LBC chamber and my new Grendel has a 6.5 Grendel II chamber. Both were match with Grendel II bolt.

Oddly enough i use both kinds of brass and even the same load for each brass. Really accurate and fun. There is a custom barrel I have my eye on now to make a custom cast bullet 6.5 Grendel to really milk this little guy of accuracy.

Just polish a bit more off till you can chamber the round easily.

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[Tackleberry41]

I had issues with Lee 8mm dies, not pushing the shoulder back enough. I had to shave down a shell holder to get it right. Its called tolerance stacking, it can be off +/- so much on each part. So a shellholder a little thinker than designed, a die a little longer than supposed to be. I measured the shell holders, they were all over the place on thickness.

[CPC24]

I shaved the shellholder down about .004, and it helped. They chamber, but only extract when fired. The Grendel brass I found is PPU, with large primers. It has the Grendel headstamp, but has the same weight as converted 7.62. It’s been fired in a Grendel chamber, though, so it chambers. It’s not a huge price difference in once fired cases. Grendel is .40/each, while 7.62 is about .25/each.

[CPC24]

I fixed it! Some of the Grendel brass didn’t want to chamber, and I realized the chamber may have burrs. I polished it and the feedramps really well. Tiny bits of metal came out. I tried the “plink” test, and even the converted ones fit. I did a whole magazine of them without sticking.

[CPC24]

I looked at the chamber with a bright light after I lapped it. The shoulder angle is just a .001 or so less sharp now. I guess it had a few burrs, and they were digging into the brass. I shot a couple weak fireforming loads, and they extracted easily. At least I don’t have to pull all my converted handloads now!

[Sig556r]

Chamber type should not affect properly sized brass (even un-fireformed) as long as the mating bolt is recessed correctly.
If you have a Grendel I bolt & Grendel II chamber or vice versa, brass will not fit.
Got both types, either one shoots 7.62x39 converts all day long, but I size with Hornady dies though.

[CPC24]

The bolt and chamber are both Grendel II. The lugs lock perfectly, and the extractor works fine. The cases were sticking in the rough chamber.

[CPC24]

I shot and fireformed all the brass. I had to manually feed some of them, but now they chamber perfectly when reloaded. The chamber stopped scratching them, so I got all the burrs out.

[CPC24]

One of the cases blew up on me yesterday! I’m okay, though. I was wearing safety glasses, and felt the extractor bounce off my head. Gas went everywhere. The mag blew out the bottom and bulged out! It wasn’t the load; it was a recalled 6.5G PPU case, not a 7.62. I actually bent the mag back into shape with a good one, and it works now! The rifle is fine; I ordered a new extractor. I’m just blessed I didn’t lose an eye!

[Rcmaveric]

One of the cases blew up on me yesterday! I’m okay, though. I was wearing safety glasses, and felt the extractor bounce off my head. Gas went everywhere. The mag blew out the bottom and bulged out! It wasn’t the load; it was a recalled 6.5G PPU case, not a 7.62. I actually bent the mag back into shape with a good one, and it works now! The rifle is fine; I ordered a new extractor. I’m just blessed I didn’t lose an eye!

Well dam, glad you are okay. How did you know it was a recalled case?

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[CPC24]

PPU recalled all of their 6.5 Grendel brass. I called them and said they don’t cover once fired cases. They didn’t blow up the first time, technically... The seller is going to send me a batch with a different headstamp. I bought some new Remington 7.62x39 SRP cases at the LGS, and they resize perfectly. The case head comes out at .437-.438, which is perfect.

[CPC24]

The cases are definitely too thin! They hold 26-27 grains of water, instead of 25. They also weigh at least 10 grains less.

[Sig556r]

I mostly reload 6.5 with fireformed 7.62x39s Win, FC & Fiochi headstamped brass. The latter is the thickest, but once fireformed, size like the rest. I stay away from factory PPU & keep Hornadys for load dev. PPUs tend to have loose primer pocket, you can feel them when you prime manually compared to other headstamps.