6.5 Grendel Brass Mystery

nmxdaven · November 15, 2016, 09:18 PM

Hey guys.

Posted this over on the 65 forums, but thought I would ask here too.

I have a recent 6.5G build. Running a Satern 24" with the brownells supplied bolt.

I broke it in with some wolf steel case to set the adjustable gas block and break it in. I then ordered 600 rounds of Hornady 123 Amax to start shooting and building my brass stock.

First time out I ran 40 or so rounds. Brass looked good. No issues. .5" groups at 150y.

Second time out I took 50 rounds, and the first few looked perfect. Just like ALL of the previous brass.

Then I started to get brass that looked like this.

Primer looked fine, no other signs of anything strange. Cant feel anything with a paper clip.

Measurements as follows.

"Normal fired case": 1.514
Ringed Brass: 1.517
Ringed Brass: 1.517
Raw Brass: 1.511

All ammo from same lot. Rifle wasn't even cleaned in-between.

Head-space was checked when assembled. I don't have a 6.5 go-nogo, will have to meet up with my buddy who has them soon to recheck, but seems unlikely.

Any ideas?

waveslayer · November 16, 2016, 02:05 AM

Is the case cracked or just a line around the case? What does the primer look like

My wife thinks I only have 3 guns

HiBC · November 16, 2016, 02:49 AM

No experience with a Grendel myself.

It looks to me like the necks are pretty grungy.I'm not sure of all the nuances of necking down, hot load,mild load ,ignition,etc,but the necks might be hard or thick.Gas is getting around the outside.

You switched bullets,so how the ogive engages the rifling vs where the bullet base and case mouth are might matter.Your rifle may not like that bullet or the trim might be short?
Another potential issue.Its a 24 in bbl and it seems a lot is hanging out past the gas block.Thats dwell time of full gas pressure in the bbl after the gas block.Its longer than most AR's.

Did you choke your adj gas block down till it just reliably stays bolt open last round?

That line might just be a witness line from where some gas vented out the rear of the chamber.

You might want to clean your chamber.

You said it passes paper clip test.I know the brass is precious,but cut one lengthwise .

There!! I didn't tell you much

nmxdaven · November 16, 2016, 03:58 PM

Primer looked perfect.

Someone mentioned that theory over on the 65 forums too. I set the gas block on the slower wolf ammo, so I figured it would likely be on the low gas side with the hornady. I will turn the gas block down a few notches and see if that clears the brass up.

Thanks for the help!

Wyosmith · November 16, 2016, 04:44 PM

Most of the 6.5s I have made do that.
It's not a problem if the headspace is OK. It's just how the brass is getting burnished by the chamber and the loading dies.

November 15, 2016, 09:18 PM	#1
nmxdaven Junior Member Join Date: November 5, 2008 Posts: 6	6.5 Grendel Brass Mystery Hey guys. Posted this over on the 65 forums, but thought I would ask here too. I have a recent 6.5G build. Running a Satern 24" with the brownells supplied bolt. I broke it in with some wolf steel case to set the adjustable gas block and break it in. I then ordered 600 rounds of Hornady 123 Amax to start shooting and building my brass stock. First time out I ran 40 or so rounds. Brass looked good. No issues. .5" groups at 150y. Second time out I took 50 rounds, and the first few looked perfect. Just like ALL of the previous brass. Then I started to get brass that looked like this. Primer looked fine, no other signs of anything strange. Cant feel anything with a paper clip. Measurements as follows. "Normal fired case": 1.514 Ringed Brass: 1.517 Ringed Brass: 1.517 Raw Brass: 1.511 All ammo from same lot. Rifle wasn't even cleaned in-between. Head-space was checked when assembled. I don't have a 6.5 go-nogo, will have to meet up with my buddy who has them soon to recheck, but seems unlikely. Any ideas?

November 16, 2016, 02:05 AM	#2
waveslayer Senior Member Join Date: August 22, 2013 Posts: 246	Is the case cracked or just a line around the case? What does the primer look like My wife thinks I only have 3 guns

November 16, 2016, 02:49 AM	#3
HiBC Senior Member Join Date: November 13, 2006 Posts: 8,283	No experience with a Grendel myself. It looks to me like the necks are pretty grungy.I'm not sure of all the nuances of necking down, hot load,mild load ,ignition,etc,but the necks might be hard or thick.Gas is getting around the outside. You switched bullets,so how the ogive engages the rifling vs where the bullet base and case mouth are might matter.Your rifle may not like that bullet or the trim might be short? Another potential issue.Its a 24 in bbl and it seems a lot is hanging out past the gas block.Thats dwell time of full gas pressure in the bbl after the gas block.Its longer than most AR's. Did you choke your adj gas block down till it just reliably stays bolt open last round? That line might just be a witness line from where some gas vented out the rear of the chamber. You might want to clean your chamber. You said it passes paper clip test.I know the brass is precious,but cut one lengthwise . There!! I didn't tell you much

November 16, 2016, 03:58 PM	#4
nmxdaven Junior Member Join Date: November 5, 2008 Posts: 6	Primer looked perfect. Someone mentioned that theory over on the 65 forums too. I set the gas block on the slower wolf ammo, so I figured it would likely be on the low gas side with the hornady. I will turn the gas block down a few notches and see if that clears the brass up. Thanks for the help!

November 16, 2016, 04:44 PM	#5
Wyosmith Senior Member Join Date: December 29, 2010 Location: Shoshoni Wyoming Posts: 2,713	Most of the 6.5s I have made do that. It's not a problem if the headspace is OK. It's just how the brass is getting burnished by the chamber and the loading dies.