Grendel Bolt Problem?

[shelbydaniel]

So I have been itching for an AR platform Grendel since shooting my buddies and I found one used on Snipers Hide. It looked nice and came with 300 rounds of ammo and several mags so I went ahead and bought it. Here are the basic specs:

Aero lower
Elfmann 3 gun trigger
Magpul Miad
Ace stock
Black hole 264 lbc 22" SS barrel TYPE 1
BCM KMR15 rail
Jp 6.5 bolt
PRI heavy BCG
PRI charging handle
Aero Upper

^^Anyone notice something that doesn't fit?

The seller told me the prior owner ran 300 thru it with no problems, and he ran 30 thru it with no problems. After receiving it and properly mounting my Vortex PST, I had problems getting the SST Hornady to chamber, then on the 5th shot the JP enhanced extractor broke...

The Hornady brass on 3 of the 5 rounds was bulged near the bottom of the case. I called JP and they told me they don't make a Type 1 bolt...

I have bought a 7.62x39 bolt from RGuns and one of the mods over at the BHW forums told me that will most likely fix the issue.

I find it hard to believe anyone ran 300 rounds thru this gun with no problems.

What are your thoughts?

On the bright side, looks like I'll have a type 2 JP bolt for sale. I ordered a replacement enhanced extractor from them today. They're some very helpful and friendly folks on the phone.

[LR1955]

So I have been itching for an AR platform Grendel since shooting my buddies and I found one used on Snipers Hide. It looked nice and came with 300 rounds of ammo and several mags so I went ahead and bought it. Here are the basic specs:

Aero lower
Elfmann 3 gun trigger
Magpul Miad
Ace stock
Black hole 264 lbc 22" SS barrel TYPE 1
BCM KMR15 rail
Jp 6.5 bolt
PRI heavy BCG
PRI charging handle
Aero Upper

^^Anyone notice something that doesn't fit?

The seller told me the prior owner ran 300 thru it with no problems, and he ran 30 thru it with no problems. After receiving it and properly mounting my Vortex PST, I had problems getting the SST Hornady to chamber, then on the 5th shot the JP enhanced extractor broke...

The Hornady brass on 3 of the 5 rounds was bulged near the bottom of the case. I called JP and they told me they don't make a Type 1 bolt...

I have bought a 7.62x39 bolt from RGuns and one of the mods over at the BHW forums told me that will most likely fix the issue.

I find it hard to believe anyone ran 300 rounds thru this gun with no problems.

What are your thoughts?

On the bright side, looks like I'll have a type 2 JP bolt for sale. I ordered a replacement enhanced extractor from them today. They're some very helpful and friendly folks on the phone.

Shelby:

Did you ask the seller what ammo he fired through the rifle?

I have rifles that use both types of bolt.

You can use a Grendel bolt with barrels cut for both bolts. This is because the Grendel bolt face is slightly deeper than a 7.62 X 39 bolt face. However, a Grendel bolt and a chamber cut for the 7.62 X 39 bolt face will blow the shoulders out a little bit. They will function but you will notice the distorted brass at the shoulder. A 7.62 X 39 bolt and a chamber cut for the Grendel bolt will not go into battery.

So, my guess is that the issue is probably the SST. However, LRRP52 is way more experienced with Grendel mechanical problems so I defer to him.

Oh yes, did I say that I never trust anyone selling a used rifle unless that person is a trusted friend?

Put the other bolt into it and see if it will chamber anything. If it doesn't go into battery with a sized piece of brass than extract easily, you got some bad advice.

LR55

[earl39]

That's saying just because it will chamber it is safe. B.S. That is the most dangerous thing you can say. Just because a 308 will fire IN a 30-06 doesn't make it ok much less safe. Wrong bolt equals wrong headspace equals dangerous situation even if it doesn't cause a catastrophic failure.

[schrödinger's cat]

I don't know either of you, but given 1955's reputation and the fact that has been a firearms instructor for much of his life, I'm goon to assume that he doesn't give dangerous advice. It may be that he is familiar with both bolt face depths and for this cartridge if it will chamber them the bolt depth is sufficient to hold up to the pressure of the round.

[A5BLASTER]

Your barrel is marked for a type 1 so as long as you are running a type 1 bolt from what I have learned and understand through this site you should be good to go.

I dont know much about the 7.62x39 bolt you bought what is the diffrence between it and a 6.5 grendel type 1 bolt.

[LR1955]

That's saying just because it will chamber it is safe. B.S. That is the most dangerous thing you can say. Just because a 308 will fire IN a 30-06 doesn't make it ok much less safe. Wrong bolt equals wrong headspace equals dangerous situation even if it doesn't cause a catastrophic failure.

Earl / Guys:

I am not saying just because it chambers it is safe. Only that in this specific situation given these specific conditions, it will work and no, you won't blow up your rifle. Why do I say this? Because I have done it in the vain attempt of seeing if I could get a bit more powder into a more blown out case. It was a total failure so I don't recommend it be tried. You won't increase the case capacity enough to warrant all the crap you will go through trying to get a sizing die to full length size it without setting the shoulder back to original specs. All it did was ruin some Lapua brass in the process.

A Grendel bolt is basically a 7.62 X 39 bolt with the bolt face a bit deeper. .0125" I believe, but don't quote me.

Chambers are cut according to the bolt being used due to headspace issues.

A Grendel bolt can work in a chamber cut for a 7.62 X 39 bolt. Headspace would be excessive according to SAAMI specs but it will work. The shoulders will appear a bit rounded because they were blown out .0125".

On the other hand, if you try a 7.62 X 39 bolt in a chamber cut for the Grendel bolt, the round will not go into battery so you don't have to worry about insufficient headspace being a danger. The thing will not go into battery at all. Not even enough for a out of battery firing.

Another way to do it is just to use empty brass. One of the bolts will work unless the entire chamber was cut for a completely different cartridge. For the bolt that works, put soot on the shoulder and chamber it again. If you see soot removed from the shoulder, I would say you just found the right bolt.

We used to blow out 6 PPC brass by seating bullets long enough so they jammed into the rifling, thus supporting a case that is woefully insufficient in headspace, so it would fire. The bullet pushed the brass back on to the bolt face so the firing pin would detonate the primer. I would say that was insufficient headspace on a much grander scale. Can't imagine the pressure spike either. Never blew up a rifle doing that either. The resulting brass had to be sized and fired again before it finally took to the chamber. Other guys went through the process of making a false shoulder in order to get them to shoot. A false shoulder is better than jamming the bullet into the rifling no doubt but it entailed more work and was by no means headspaced because only a little bit of the neck was hitting the chamber. Either way, the brass was so overworked by doing this that it never lasted real long.

So, we went to 7.62 X 39 brass and sized it down then shot it to fireform. Problem was it held much less powder so the velocities were very slow. And it only went about five shots before the primer pockets opened up or you split a neck.

No, I do not recommend shooting ammo through chambers that are not headspaced properly. In this case though, it won't blow up the rifle.

Hope that clarifies things for you fellows.

LR1955

[shelbydaniel]

I received my 7.62x39 bolt today. After install, it cleanly chambered a full 10 round mag with ease. I plan to shoot it tomorrow but it appears that this has fixed the problem. My type 2 JP enhanced bolt is now listed on the exchange forum for sale if anyone needs a nice used type 2 bolt.

I'll report back on how it shoots tomorrow. It's supposed to be 70 degrees and sunny here in North MS.

[LR1955]

I received my 7.62x39 bolt today. After install, it cleanly chambered a full 10 round mag with ease. I plan to shoot it tomorrow but it appears that this has fixed the problem. My type 2 JP enhanced bolt is now listed on the exchange forum for sale if anyone needs a nice used type 2 bolt.

I'll report back on how it shoots tomorrow. It's supposed to be 70 degrees and sunny here in North MS.

Wow!

That is a surprise. The Grendel bolt should have chambered the cartridges as well given the chamber is cut for a 7.62 X 39 bolt.

I think something is not right with the Type 2 JP Enhanced bolt you have if it would not chamber anything.

Well, we will find out if someone buys it.

LR55

[shelbydaniel]

The JP bolt looks fine to me. I bought a brand new JP enhanced extractor for it.

I've had more than one person tell me that a type 2 bolt would not chamber rounds correctly in their type 1 BHW barrel.

I'll be glad to give the buyer a money back guarantee if the bolt doesn't work, but like I said it looks fine to me after replacing the broken extractor.

[A5BLASTER]

Yep thats the way I understand it type 1 bolt with type 1 chamber and type 2 with type 2 chamber.

[LRRPF52]

This whole business of Type I and Type II only confuses things, so it really helps if you identify bolts by what they are. The reality is that there are all kinds of them.

For starters, a Colt 7.62x39 Sporter bolt is a different animal, engineered around the Russian short cartridge back in the 1980's, then forgotten by most. It had a deeper face so the extractor could be engineered around the thicker case rim of the Soviet x39.

When other companies figured they could make 7.62x39 AR's too, they assumed that they could just use all the same dims, but a wider bolt face for the fatter case head. This was a major mistake and false assumption. Reason is that extractors now end up with a thinner lip, since the extractor groove needs to be larger for the thicker case rim. The legacy of broken extractors and bolts for 7.62x39 AR15's proves that point. Even the DPMS LR-308 uses a shallow bolt face depth at ~.124", and they break or bend extractors all the time, and those extractors are significantly wider than AR15 extractors. ArmaLite Inc. uses a deeper bolt face depth, and I have yet to see their break. It certainly isn't a regular thing like on the LR-308.

This is why AA went with a deeper bolt face for the .50 Beowulf, which uses a rebated head matching the dims of a 7.62x39 case. Then came the 6.5 Grendel.

Since so many companies have spit out bolts they thought would be good for 7.62x39 with a ~.125" bolt face depth, it has driven more demand for that bad dimension.

The AA 6.5 Grendel bolts have a deeper face, a purpose-built extractor for the thicker rim, a higher-strength tool steel material that is QC'd heavily, tuned dimensions to prevent binding, slamming of the lip face against the case head when going into battery, and less extractor lift for optimum feeding.

There is a lot going on with them that I never knew about years ago when I first got into this cartridge. I remember seeing posts on the forum back in the day where many people thought that AA was taking 5.56 bolts, opening the faces, and going with that, but they have been spec'd out from scratch with specific alloys, heat treating, MPI, and destructive testing to ensure a durable, reliable bolt.

The overall length isn't even the same, and you could not physically turn a 5.56 bolt into a Grendel bolt if you tried for that reason, which allows standard firing pins to be used without excessive firing pin protrusion.

The terms "Type 1" and "Type 2" have no real meaning when it comes to 6.5 Grendel bolts or "7.62x39" bolts. It's either built right from scratch, or it's not. The more I have researched into it, the more I see how different they are, and I have had many samples come through my hands and calipers over the years.

[LR1955]

The JP bolt looks fine to me. I bought a brand new JP enhanced extractor for it.

I've had more than one person tell me that a type 2 bolt would not chamber rounds correctly in their type 1 BHW barrel.

I'll be glad to give the buyer a money back guarantee if the bolt doesn't work, but like I said it looks fine to me after replacing the broken extractor.

Shelby:

Ok -- I certainly will believe that.

'Back in the day' as they say, we had two choices. Either a bolt made by Alexander or a 7.62 X 39 bolt. I can see the Grendel bolt not being quite right with a chamber cut for a 7.62 X 39 bolt due to excessive headspace but I believe you reported the bolt wouldn't go into battery. That should not have been the case. Since I have a JP Grendel upper, I will try its bolt in one of my 7.62 X 39 bolt headspaced Grendels. Am curious if it will chamber. Won't shoot it though. No need to put unnecessary stress on things anymore. We had to do it then to get something to work because we could not get Grendel brass. No need today.

Seeing what LRRP52 has written about the various bolts these days I imagine people have messed around with the design of the bolts themselves, making it even more difficult to do something simple like buy a new bolt and expect it to work.

Glad your rifle is functional again and I imagine someone will pick up a good bolt.

LR55

[Bill Alexander]

When I started out with the Beowulf all those years ago there simply was not such a thing as a 7.62x39 bolt. There was a residual of the old Colt sporters, most of which were broken due to the excessive dirt groove Colt used but that was it. No one made a 7.62 bolt. For the first 8 years at least the 0.136" bolt face was the standard because I was the only one making them and probably ended up making more than Colt.

The whole type 1 and type 2 situation was created by BHW as they flip flopped between whatever bolt they could lay hands on and then tried to justify it to the customers.

If a bolt broke it was always the fault of the cartridge or "Bill Alexander is a bastard" making propriety parts.

[rabiddawg]

I have a name for Bill Alexander, he is THE MAN!

I wish a mod would change the name of the thread because it is not a Grendel bolt problem rather a les Baer custom problem.

This is another reason I will run nothing but a saami 6.5 Grendel chamber. If I need a part for one of my two AA rifles guess where I am going for that part. If I need a part for one of my PF guns guess where I am going. See where I'm going with this?

All this bs confuses me and I'm on here many times a day reading. I can't imagine what it does to folks that may want to get into the round. It's a shame really. Or is it a sham? Hmmm.

[LRRPF52]

It's really not a problem if you get the barrel/bolt combo from a reputable vendor.

A lot of the different barrel and rifle makers have been getting bolts from AA for years, and headspace off that anyway.

Last I checked, JP, Les Baer, PF, Satern, Lilja, J&T/Doublestar, and several others headspace to actual Grendel bolts. There is no way anyone is going to do the same amount of legwork that has been done when you really look at the years of RDT&E that went into it, as well as the Quality Control standards AA implements with MPI and destructive testing.

I wish the rest of the market would implement those types of controls on their 5.56 bolts as well. There have been some big name manufacturers even that got caught stamping "MPI" on their 5.56 bolts, when the testing wasn't even done, particularly during the post Sandy Hook panic.

When I got into this, I figured the Grendel bolts were a simple machine modification. I couldn't have been more wrong in that assumption. Rather than being confused, just get your barrel and bolt from the same place, or from someone who we know headspaces to the Grendel bolt face depth and lug length.