6.5 Grendel chamber question

[bikemutt]

I recently installed a new Odin Works 6.5 Grendel barrel in an AR15 upper receiver. After break in using Hornady 123 gr AMAX factory ammo and thoroughly cleaning everything I set about measuring up for some hand loading. With a Hornady OAL gauge and 120 AMAX bullets, I measured 2.237" OAL with the bullet fully engaged with the rifling. I did this several times to check my work and confirmed I can see where the bullet clearly contacted the rifling.

The Hornady 10th edition load book recommends a COL of 2.245 for a 120 gr AMAX, 6.5 Grendel.

So, in theory, if I load this cartridge to book at COL 2.245", either the bolt won't close, or it'll perform final seating with a jump of 0". Or maybe something else I don't know about, yet.

The other side is maybe I measured something wrong, or I assembled the barrel to the upper receiver wrong. Empirically the rifle experienced a remarkable number of jams with the factory 123 AMAX rounds, stovepipes in all cases. Granted this barrel came with an adjustable gas block which I used SOP to adjust but, this isn't my first adjustable gas block rodeo. And, I was using metal 7.62x39 magazines. I mention these factors in order to paint a more complete picture of the experience.

I'm mostly concerned about the apparent shortness of the chamber if in fact that is the case. Thoughts on the matter greatly appreciated.

 

[CarJunkieLS1]

Odin Works not that long ago had a bad batch of barrels maybe yours is effected.

 

[CarJunkieLS1]

Also make sure you are using the correct bolt. With two different bolt types and several different chamber designs things can get messed up fairly easily.

 

[ants]

Bike Mutt, he's right about the headspace in Post #3. Alexander Arms changed it a couple years ago, you need to match the bolt the barrel.
Other aftermarket manufacturers didn't change it, but some followed Alexander's lead. Just take a deep breath and check it out.
But maybe that's not your problem. Maybe you might reconsider your understanding of OAL in the published data.

The published manufacturer's data is NOT NOT NOT a 'recommended' OAL. It is simply the OAL they used in their pressure test.
You are free to adjust OAL to your specific rifle. An OAL that jams the bullet into the lands can result in extra pressure.
You checked your OAL with the Hornady gauge (bravo!) so seat the bullet a little deeper to make sure you don't jam the lands.
Then do your normal workup. Start low and move up slowly. You always knew how to do that, have confidence and proceed accordingly.

I know it's hard to accept that the OAL is NOT a recommended OAL. But if you can realign your head, it will make better sense.
The manufacturers use test barrels in a unique pressure barrel machine. They have NO IDEA of the dimensions of your chamber.
So they are not 'recommending' an OAL because they have no idea of what fits your chamber. They are simply reporting the OAL they used.

Depend upon your own OAL wisdom from your Hornady gauge. It is real life data, not an assumption.

I hope this helps.

 

[bikemutt]

Bike Mutt, he's right about the headspace in Post #3. Alexander Arms changed it a couple years ago, you need to match the bolt the barrel.
Other aftermarket manufacturers didn't change it, but some followed Alexander's lead. Just take a deep breath and check it out.
But maybe that's not your problem. Maybe you might reconsider your understanding of OAL in the published data.

The published manufacturer's data is NOT NOT NOT a 'recommended' OAL. It is simply the OAL they used in their pressure test.
You are free to adjust OAL to your specific rifle. An OAL that jams the bullet into the lands can result in extra pressure.
You checked your OAL with the Hornady gauge (bravo!) so seat the bullet a little deeper to make sure you don't jam the lands.
Then do your normal workup. Start low and move up slowly. You always knew how to do that, have confidence and proceed accordingly.

I know it's hard to accept that the OAL is NOT a recommended OAL. But if you can realign your head, it will make better sense.
The manufacturers use test barrels in a unique pressure barrel machine. They have NO IDEA of the dimensions of your chamber.
So they are not 'recommending' an OAL because they have no idea of what fits your chamber. They are simply reporting the OAL they used.

Depend upon your own OAL wisdom from your Hornady gauge. It is real life data, not an assumption.

I hope this helps.

Thanks ants, that does make sense.

As far as the bolt goes, this barrel came with a complete bolt and carrier, it's a package deal.

My plan is to load these to an OAL of 2.210" or a bit less, to stay out of the rifling. The SAAMI minimum OAL is 2.135" so I'm not up against that limit.

 

[bikemutt]

Odin Works not that long ago had a bad batch of barrels maybe yours is effected.

Thanks CarJunkieLS1, I looked up the Odin Works 6.5 Grendel recall. The test to know if a particular barrel is affected is to drop an unfired round upside down into the chamber, if it sinks in to where only the bullet shows above the chamber, it's a bad one. My barrel does not do that, it matches the good barrel picture. So, I'm thinking its OK at this point.