Chamber Question

[mac37]

I'm new to the Grendel. I just bought a Specialized Dynamics 20" .264 LBC upper. I was led to the LBC because I was told it would shoot both Grendel and 264 ammo. Anyway... I bought some Wolf and Hornady ammo from Alexander Arms. The upper functioned fine, shot all the Hornady ammo fine with descent accuracy but 2 to 3 rounds per box of the Wolf would not fire. They had light primer marks. I didn't think too much about it thinking it's just the Wolf ammo. Moving on I bought some AA brass (Lapua) and loaded some 120g SMK's. They won't fire just like the Wolf. I took some measurements with a comparator gauge and the Wolf and AA brass is shorter than the Hornady and much shorter than the fired brass. So, here's the question. Is my chamber cut wrong and is there any way to correct it? On a side note, the accuracy with once fired brass is much better than new ammo. Best preforming is 28g Vit 140, 120g SMK's in the Hornady brass with shoulders bumped back .002. Thanks for reading and any help is appreciated.

[RangerRick]

If they had light firing pin indentations the bolt wasn't fully in battery. The brass probably needed the shoulders bumped back a little, but you may want to load one then eject it to check for rifling marks on the bullet.

Any pressure signs on the fired brass?

The Grendel chamber has a compound throat (starts at one angle then has a different angle the rest of the way). This was done to work with a wide range of bullets. The .264 throat has one angle and some throats are .295 and others are .300.

The brass is identical for both but the LBC was designed for the Black Hills loads sold by Les Baer.

If you reload you won't have any trouble once you get everything set up.

You need to get an ammo gauge. Alexander Arms sells a nice one for $30. You can find it in their catalog under reloading accessories. If your sized brass or new rounds fit in it, it should chamber. If they fit in the gauge and won't chamber, you may have a chamber problem, but that would be unusual.

When you say the fired brass is longer, exactly what length is it? Longer than the Alexander Arms spec of 1.526? See: http://alexanderarms.com/images/pdfs/grendel_reloading.pdf

RR

[mac37]

I'm thinking you're right. It's not going into battery. The unfired round just falls out of the chamber.
The extractor never picks up the rim of the case.
No rounds fired had any pressure signs.
Here are some measurements from the shoulders with a comparator gauge
Hornady New 1.189, Fired 1.208
Wolf New 1.181(will not fire), Fired rounds 1.207
AA (Lapua) Brass 1.181 (will not fire)

OAL of brass Hornady range 1.515 to 1.520
AA (Lapua) 1.514 to 1.517

I also measured the base of the case right above the rim and the rim

Hornady Above .437, Rim .052
AA (lapua) .439, Rim .058

The rifle is supposed to have a 264 LBC Chamber but bolt is marked AA. I don't know if it makes a difference using an Alexander Arms bolt with a LBC chambered barrel?

[brickcues]

The chamber on the 264 LBC AR has a neck that is .295, the Grendel is .300. The throat is also alittle tighter on the LBC AR. Wolf steel case ammo will not work with LBC AR as it measures .295 at the neck loaded and would be very tight to chamber. You can check the neck size by using calipers on the fired cases at the neck as their is suppost to be a .300 neck LBC AR also. The problems that I had with mine was that the 123 AMAX that I loaded at 2.26 were being jammed into the lands about .015 and the bolt would sometimes not close. When I reseated the bullets to 2.235 problems went away. Must check OAL to be sure bullets have about .010 jump.

[mac37]

No, the loaded rounds are not jamming into the lands preventing the bolt to go into battery. When I load the 123g A-Max to the factory length, in the once fired/resized/shoulders bumped .002 Hornady brass, they fire just fine. If I use the new AA/Lapua brass the round won't fire. I can't get the bolt to close on empty AA/Lapua cases.

[LR1955]

I'm new to the Grendel. I just bought a Specialized Dynamics 20" .264 LBC upper. I was lead to the LBC because I was told it would shoot both Grendel and 264 ammo.

Mac:

Normally a guy needs to bump fired brass in order to get it to chamber. Since you are shooting factory loads, I doubt the problem involves the Lapua / AA or Wolf brass.

Note that the all Hornady does with their brass is to change the headstamp between Grendel and .264 LBC. Just like you can buy Grendel brass with Lapua or Alexander Arms headstamps. The brass is identical in dimensions.

The first run of Grendel brass that Hornady made had problems chambering in AA chambers because the brass was too long. Just like your current situation as you have found by measuring.

Maybe who ever made your barrel cut the chamber long to accommodate this first run of Hornady brass? If they did, it is possible -- although I believe only very slightly -- that your AA and Wolf brass is so short that you are having problems with the firing pin hitting the primer hard enough to set it off.

I say this because I have deliberately fired Grendel ammunition through chambers cut for the 7.62 X 39 brass while using the Grendel bolt -- thus creating excessive headspace. All rounds fired. Also, I have fired .308 ammunition out of 30-06 chambered rifles without any problems other than destroying the brass.

Some of us never had a problem with this first run of Hornady brass but enough others did to make Hornady take note and subsequent lots of their brass has not shown any problems that have been brought to the attention of the Forum.

Les Bear and Hornady both state very clearly that .264 LBC is interchangeable with Grendel brass.

LR55

[bwaites]

Mac:

.......... Also note that if they state it is a neck diameter issue with AA using .300 and LB using .295, they are deliberately and willfully lying. AA marketed both chambers and factory loads will chamber and function perfectly with both.

LR55

This is splitting hairs a little bit, but according to Bill Alexander, AA never shipped any .295 necked rifles. CSS requested the .295 neck for some rifles and called it the "Match" chamber. Alexander felt that it compromised semi auto, and especially full auto, performance and thus refused to sell it under the AA brand. He also knew eventually there would be steel case ammo and that the .295 neck would be even more compromising. So AA didn't market he .295 neck. Bill Alexander has regretted ever drawing that chamber almost since day one because of the issues associated with it.

[mac37]

LR55,
I think you got it. It makes sense that the chamber is cut too deep. The Lapua case is set too deep in the chamber not only for the firing pin to reach but even for the extractor to pick up. As for the necks, all the fired cases measure between .298 and .300. So, it seems that the throat is .300 and the chamber is cut ~.008-.010 too deep. Could the AA bolt in an LBC chamber contribute to this? I read AA uses their own spec bolt and they will not work with other mfg's barrels and correctly headspace.

Thanks for all the help!

[RangerRick]

LR55,
I think you got it. It makes sense that the chamber is cut too deep. The Lapua case is set too deep in the chamber not only for the firing pin to reach but even for the extractor to pick up. As for the necks, all the fired cases measure between .298 and .300. So, it seems that the throat is .300 and the chamber is cut ~.008-.010 too deep. Could the AA bolt in an LBC chamber contribute to this? I read AA uses their own spec bolt and they will not work with other mfg's barrels and correctly headspace.

Thanks for all the help!

That's a dangerous gun. Did you buy it new from the manufacturer? If so send it back for a replacement. If they don't believe the problem and you want to confirm it, you can get a set of "go/no go" gauges. Midway sells them but they are out of stock there til the end of December: http://www.midwayusa.com/product/316994/ptg-headspace-no-go-gage-65-grendel-65-bpc-264-lbc--ar

Somebody else may have them in stock.

Whoever you bought it from sold you a defective gun, so you should be able to get your money back.

RR

[mac37]

Yes, I bought it new from http://specializeddynamics.com/
I've tried reaching him through another site but he hasn't responded. I'll let you know what he says when I hear from him.

[RangerRick]

Yes, I bought it new from http://specializeddynamics.com/
I've tried reaching him through another site but he hasn't responded. I'll let you know what he says when I hear from him.

Hopefully you'll hear back after the holidays. If you used a credit card you can challenge the payment through your bank if you can't get satisfaction.

Please do let us know how this goes so we can get the word out about this guy if he tries to rip you off.

I don't know the guy and haven't heard anything bad or good about him. How about the rest of you guys?

RR

[Variable]

I'm in the woods, so I don't have numbers handy, but... Do you guys think he might have a chamber cut for a 7.62x39 bolt? If he did, and was given an AA bolt with the deeper face that might account for what sounds like the headspace problem? Just wondering out loud...

[pinzgauer]

Do you guys think he might have a chamber cut for a 7.62x39 bolt?

That's my read, that or the bolt is not going in fully in battery. Even if miscut to the "longer Hornady", that would not account for the extractor not engaging. Or no Firing pin strike.

From memory most of the noise around "bad hornady" was with non-AA barrels with super tight tolerances, and even that was only LBC and LW/CSS. And was more of a shoulder radius issue than a true headspace problem. I'm not aware of any AA old or new that had issues. Certainly no one posted about them.

It's not clear from the original post if the hammer is dropping, or if it just won't snap. The second would imply not fully in battery. You can get a light firing pin dimple just from attempting to chamber a round.

In any case, something is wrong and the vendor should take care of it.

[mac37]

I'll post some pictures tomorrow. If a bolt is out of battery, I thought it was not possible for the firing pin to reach the primer?

[LR1955]

I'm in the woods, so I don't have numbers handy, but... Do you guys think he might have a chamber cut for a 7.62x39 bolt? If he did, and was given an AA bolt with the deeper face that might account for what sounds like the headspace problem? Just wondering out loud...

VB:

I have deliberately shot Grendel ammo using a Grendel bolt and a chamber cut to use the 7.62 X 39 bolt. The brass looked a bit weird when it ejected but otherwise every shot went off. Same when shooting .308 from a 30-06 chamber. They are headspace issues but they both fired.

Not sure what is the case with this one. Pretty sure we could figure it out in about fifteen seconds if we had the upper.

LR1955

[mac37]

Not sure what is the case with this one. Pretty sure we could figure it out in about fifteen seconds if we had the upper
Is that an offer to diagnosis the problem? If so, I'll send it to you. :)

[Bill Alexander]

Kudos to LR for his innate curiosity.

I have on occasion took time to lengthen/shorten bits and pieces in the Grendel system to see what works and for how long. Does the headspace effect accuracy and what is safe etc. One thing we have tried is moving the chamber forward to see just how far we can drift before problems start. Typically the Grendel allows for 0.020 of excess space over the CASE before the system will fail to fire or pick up the case on the extractor. The onset of both failure to fire and also extract is happily timed at about the same place. Accuracy is actually not absolutely dependent upon a tight headspace which is something we tried to achieve.

The OP barrel may not be dangerous but something is quite amiss.

[mac37]

The vender has returned my email and will fix the problem. I did get a no-go gauge from PTG. To use it correctly, I remove the extractor claw from the bolt? Anything else?

[scottmilk9]

That's a dangerous gun. Did you buy it new from the manufacturer? If so send it back for a replacement. If they don't believe the problem and you want to confirm it, you can get a set of "go/no go" gauges. Midway sells them but they are out of stock there til the end of December: http://www.midwayusa.com/product/316994/ptg-headspace-no-go-gage-65-grendel-65-bpc-264-lbc--ar

Somebody else may have them in stock.

Whoever you bought it from sold you a defective gun, so you should be able to get your money back.

RR

Ranger Rick, I don't appreciate your speculation and posting negative comments like this on a public forum unless you actually see first hand what the problem is and/or you are qualified to determine what the problem is.

Mac37 couldn't get a hold of me because I was out of town hunting and saw an email on my phone and responded as soon as I had signal.

I can assure everyone that John will be taken care of and will make it 100% right after we diagnose the problem properly. Thanks JohnScott@ Specialized Dynamics

[RangerRick]

Ranger Rick, I don't appreciate your speculation and posting negative comments like this on a public forum unless you actually see first hand what the problem is and/or you are qualified to determine what the problem is.

Mac37 couldn't get a hold of me because I was out of town hunting and saw an email on my phone and responded as soon as I had signal.

I can assure everyone that John will be taken care of and will make it 100% right after we diagnose the problem properly. Thanks JohnScott@ Specialized Dynamics


Hi John Scott,

I don't give a crap what you think about my posts. I'll speculate about whatever I please. If the man had a functional gun, there would be no discussion.

I'm glad you are going to fix it, I hope the owner keeps us informed about the situation.

Your customer service leaves something to be desired if your customers have to come here for help because they can't reach you or your associates.

I understand it was Thanksgiving weekend, so I'm sure we are willing to cut you some slack on that.

Your reputation with this community will depend on how you treat this guy and others like him.

From what he described it was a gun I wouldn't shoot until fixed.

I'm sure we'd all like to hear what the problem was, so please do post about it when you find out.

RR

[bwaites]

Gentlemen, I appreciate the concerns here, but please act in a respectful manner to all concerned.

[RangerRick]

The vender has returned my email and will fix the problem. I did get a no-go gauge from PTG. To use it correctly, I remove the extractor claw from the bolt? Anything else?

Not necessary to remove the extractor. Some people with bolt guns like to remove the ejector so they can feel how the bolt closes a little better.

Just drop the gauge into the chamber and ease the bolt closed. Bump the forward assist if you need to get the extractor over the groove of the gauge.

With an AR it's a little difficult to tell if the bolt is completely closed, so take a good look at it when it's closed on an empty chamber and notice how far forward the carrier goes.

You can also do this with the lower removed so you can see the back of the bolt carrier. Note where it is when the bolt is closed on an empty chamber.

You may also be able to see enough of the bolt in the gap at the front of the carrier to tell if the rotational position of the bolt is the same with the gauge in.

Good Luck!

RR

[RangerRick]

Gentlemen, I appreciate the concerns here, but please act in a respectful manner to all concerned.

Will Do. I'm glad he takes it personally, it shows he cares what people think of his reputation and his products.

I'm willing to concede that my statement that the manufacturer "sold you a defective gun" was premature. The gun could have been damaged in shipping somehow. But that's unlikely without the customer seeing the damage to the packaging or the rifle.

I'll be interested to hear what the problem was.

If John Scott can show us that the failure of this gun was something that happened to the gun after it left his hands, and also not defective parts or workmanship, I'll humbly and publicly apologize and ask that my critical post be removed from the forum.

RR

[bwaites]

Actually, if he fixes the issue, and comes back and explains the problem, whether an error on his end (which happens, even to the really good builders!), or elsewhere, I will respect him and his company.

[RangerRick]

Actually, if he fixes the issue, and comes back and explains the problem, whether an error on his end (which happens, even to the really good builders!), or elsewhere, I will respect him and his company.

I agree. Anybody can get a bad part from a supplier that passes testing but fails for the user. I'm a little less forgiving of a gun that gets shipped with problems, but I understand it does happen once in awhile, even with the best. Although when they fix it I would hope they change their testing protocols to be sure it doesn't happen again.

But they would get major points for honesty, if they admitted a problem, fixed it and did right by the customer.

RR

[RangerRick]

I'll post some pictures tomorrow. If a bolt is out of battery, I thought it was not possible for the firing pin to reach the primer?

It might reach it, but it's not supposed to be able to strike deep enough to fire the primer. That's based on how far the bolt is rotated. The firing pin's forward motion is stopped by it's flange hitting the back of the carrier. When the bolt rotates fully into battery it allows the carrier to move forward far enough for a good strike on the primer.

If it's way out of battery the hammer and back of the bolt carrier are designed to keep the hammer from getting a good hit on the firing pin. If it's far enough out of battery, the hammer should not release. You might still get a very small primer dent by the momentum of the firing ping flying forward on closing, if it almost goes into battery.

Problems arise if you have several parts that are out of spec, or even in the corner of a spec, that combine in such a way as to allow an unsafe situation.

If the carrier is milled too deep for the firing pin, or the cam slot milled a little off, or the firing pin itself milled a little off, or somebody accidentally gives you one of those 7.62x39 firing pins that protrude a little farther, or the bolt lugs are milled a little off, or the lugs in the barrel extension are a little off, or the head space between the barrel and extension is a little off, or the shape of the hammer is a little off, you can get problems.

One or two of these things probably aren't going to cause a problem, but if you get several, maybe combined with a primer that is not quite seated far enough into a case, you can have a serious problem.

The AR design is very clever and they spent a lot of time designing them to be safe. They did a lot of analysis of failure modes like the ones listed above and tried to spec it out so that it would be safe with common manufacturing tolerances and with parts as they become worn.

These days, with everybody and his brother making parts, you don't have any guarantee they they are mil spec or to Grendel spec.

The first Grendel bolt I got was milled slightly off center. So the metal under the bolt lugs was slightly thinner on one side. The firing pin hit close enough to the center that it always fired, but a lug eventually failed.

The manufacturer did a very thorough job of testing the bolt after failure and determined that in addition to the off center milling, it had not been heat treated properly. I'm sure they had an interesting conversation with their supplier. There was no damage to the gun and I got a new bolt, but it can and does happen now and then.

Better to play it safe and get it checked out.

RR

[scottmilk9]

Gentlemen, I appreciate the concerns here, but please act in a respectful manner to all concerned.

It will always be a respectful manner, I will never bad mouth another person on here, but with how the internet works, it can ruin someones reputation by a few bad posts.

Ranger Rick, I will sure post what the problem was, I'm not too proud to admit that there might have been an error, but I want to determine that even before I speculate. It was test fired with Hornady 123gr Amax factory ammo and functioned flawlessly. Even John said he fired it with factory ammo with no errors. I had a discussion with another gentleman about his AA brass being shorter than hornady brass, brad new out of package, I don't think thats the problem, but there are a number of things it can be and I'll make sure to look at them all. The gun is enroute to me already and will post up, at least for a learning experience for all of us what the problem was. Thank you all!
Scott

[bwaites]

Scott,

Just as a helpful point, (and you probably already know this, but I'm posting for those here who might not) Alexander Arms brass is made by Lapua, (The only difference in Lapua and AA brass is the headstamp.) Lapua brass tends to be on the extreme small side of the spec for brass, (small enough that my dies don't even resize new brass at all) while Hornady is on the top end end of the spec size wise. In fact, the Lapua brass is sized such that I have 20 firings on some of mine and have never had to trim it.

I've never heard of that difference causing this issue, but if it did, I can see where tolerance stacking MIGHT be the cause.

We look forward to hearing what you find, and appreciate you joining the board.

[scottmilk9]

Scott,

Just as a helpful point, (and you probably already know this, but I'm posting for those here who might not) Alexander Arms brass is made by Lapua, (The only difference in Lapua and AA brass is the headstamp.) Lapua brass tends to be on the extreme small side of the spec for brass, (small enough that my dies don't even resize new brass at all) while Hornady is on the top end end of the spec size wise. In fact, the Lapua brass is sized such that I have 20 firings on some of mine and have never had to trim it.

I've never heard of that difference causing this issue, but if it did, I can see where tolerance stacking MIGHT be the cause.

We look forward to hearing what you find, and appreciate you joining the board.

I definitely appreciate the info, I actually just purchased some of the new AA brass to measure the difference in the 3 cases, I don't think this is the issue either, but I know that on a 308 I have(i used 7/08 brass) and bumped the shoulder back too far and it wouldn't fire, so I want to eliminate that theory.
I promise I'll keep everyone posted, after I talk to John when we find the answers. Thanks

[Greyfox]

The vender has returned my email and will fix the problem. I did get a no-go gauge from PTG. To use it correctly, I remove the extractor claw from the bolt? Anything else?

A headspace gauge is a precision made tool. To prevent damage to your no-go gauge need to remove both the ejecter and extracter. To properly headspace there has to be no resistance when useing the guage.The ejecter has alot of force against the gauge and could damage it when you try to slam the bolt into it under spring tension. That is one tough spring to overcome.

Clean the chamber first. Check the bolt face and clean if needed.Then clean the no-go gauge.
Now insert the no-go gauge into the chamber.
Slide the carrier/bolt into the rifle untill you feel resistance,then stop pushing.
Now check the back of your upper receiver and see if the carrier is even with it. A no-go gauge will have the carrier sticking out the back of the receiver a small amount. If the carrier is even then you have excesive headspace.

A go-gauge will have the carrier close flush with the back of the receiver.A no-go guage will have the carrier sticking out the back.

You made a wise choice to purchase the headspace gauge.

Greyfox

[mac37]

I got the upper back from Scott and all I can tell is he changed out the bolt. I'm still waiting for an explanation. Maybe he'll post here. I'll test the upper and report back. Thanks to all who responded to my questions.

[stokesrj]

Sounds like to me he had a AA bolt and .264 LBC chamber which should have had a 7.62X39 bolt. Sorry, it's fun to speculate.

[mac37]

S
ounds like to me he had a AA bolt and .264 LBC chamber which should have had a 7.62X39 bolt. Sorry, it's fun to speculate.

I would have to agree. The only thing different is the bolt.
I put some rounds down range. No hick-ups what so ever. Spent brass has nice uniform primer marks. First target I was zeroing the scope. Top group is with Hornady brass and bottom group is with Wolf brass. Second target is with AA brass. Not bad. I'll get it broken in and do some more load development.

http://i59.photobucket.com/albums/g299/mac37/2013.jpg
http://i59.photobucket.com/albums/g299/mac37/2014.jpg

[bwaites]

mac,

Get some different powder! Varget = TOO SLOW!

The current darling is XBR 8208, but BLC-2 for 123's works great (dirty), TAC and 2520 work great for 123's, X-terminator works great for light bullets.

[mac37]

I'll load some with TAC tonight. Thanks!

[Mutt]

This is why I tell people only to buy Grendel ...... Too many "OTHER" parts out there. Use someones "Grendel Like'' barrel with the wrong bolt and you have problems. I wish everyone would just use the same specs that AA is using and quit muddling up our parts interchangability.