Chamber Question

[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.

[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.