Pressure Signs on Brass?

[therbert]

Greetings, fellow Grendelers (Grendeliers?)...

This is my first post to the forum, and I hope to pick some your more experienced brains in regards to brass showing pressure signs.

I recently built a Grendel upper using a 16" Satern stainless barrel with matched bolt for a mid-length gas system, a Palmetto upper receiver, and a nickel boron coated bolt carrier. It ws finished off with a Viking 13" free-float handguard and a Stoner helical brake.

I bought a couple of boxes of the Hornady Match ammo with the 123 gn A-Maxes for function testing and to zero the scope. It shoots really well, especially being that the first range trip was on a day less than ideal for sighting in a rifle, with a brisk quartering wind over my right shoulder. It put all of the shots into less than 2" at 100 yards, with most of them being in an area less than 1" in diameter. Before taking the rifle to the range I made sure to thoroughly clean out the barrel and chamber.

But all of the brass is showing what I would consider to be signs of high pressure -- flat primer faces (but not flowing into the firing pin recess), an impression of the bolt face on the head of the case, including the ejector recess.

I then reloaded the empties with three different loads of W748, because it was a suitable powder that I had on hand -- 25.5, 26.5, and 27.5 gns. All of these loads showed similar pressure signs, but according to my sources, these loads are well below the max load for this powder, bullet and primer combination of 29.3 gns.

I guess my question is, am I overly concerned? I've been reloading for over 30 years, and admittedly, most of it is for fairly sedate cartridges, like .308, .30-06 and .45-70. I guess the highest-performing cartridge in my stable other than the Grendel would be the .223. I have 50 brand-new Hornady cases sitting on the bench ready to be filled, but I want to be sure of what I'm doing before I load them up.

Thanks in advance for any words of wisdom.

Tom Herbert

Attached is a pic of one of the case heads.

Grendel.jpg

[JASmith]

Have you checked your max COL? Do you get land marks on the bullet when you eject an unfired case? If they are more significant than a light burnish or, worse, the bullet stays in the chamber when ejecting the unfired case, then you have a probable explanation for the apparent high pressures.

Regarding pressure comparisons, the .308 and '06 both routinely run at higher pressures than the Grendel.

Do you have any Hornady loads in the the .223?

This cartridge also runs at much higher pressures than the Grendel is supposed to run. Compare the same primer with each at nominal max loads.

You may not be able to see the difference, but it is one of the cross-check items to do.

Check other sources -- there is at least one (Hornady) that shows a higher max load.

Now for the kicker -- do a search in this forum for "Satern" and determine whether that barrel is one of the items involved in that long-running conversation. If so, that might verify the results you got for the COL check above.

[lamrith]

New to grendel myself. My reloading has been plinking ammo for pistol and 223, never running high pressures or pushing that upper envelope..

Looking at that picture I am not seeing anything that jumps out as a warning sign of anything. It is a new primer not fired to see high pressure signs on the primer. Is there something on the case I am not seeing that is a sign of high pressure?

[therbert]

I have 15 rounds of the Hornady factory ammo remaining, and used one to test the chamber. Yes, the bullet exhibits significant signs that it is coming into contact with the lands of the rifling when chambered. The bullet did not stick in the barrel, but it did require both hands pulling on the charging handle to remove the unfired round.

The Hornady rounds are 2.248-9" OAL, and my reloads are within a couple of thousandths of that, as I used one of the factory rounds to set the seating stem in the seater die, as I'm loading the same bullet.

I will do the search on Satern as you suggest.

[therbert]

After having done the suggested research, and finding out about the short chambers, I sent a respectful, non-accusatory, email to Lindsey at Satern, requesting their help to solve the problem. We'll see what kind of response I get. If they decline to remedy the problem, I guess I'll be sending the barrel to Precision Firearms if my regular riflesmith doesn't have a Grendel finishing reamer.

[LRRPF52]

Welcome. If you are jamming into the lands with factory ammo, then there is a problem.

If you do have it reamed, make sure it is with a shop that knows what they are doing, who actually has a SAAMI reamer. Manson reamers are GTG new. PF can handle it.

[therbert]

Well, after a week, there has been no reply from Satern, which is kind of what I expected, given my research here and in other places.

I've contacted the Pete Pieper, of Precision Barrelwork in Hempstead, Texas, who has done some great work for me before, to see if he has a reamer. He mainly does bolt-action benchrest and precision rifles, so I kind of doubt that he has a reamer on hand. But I always like to check with him first, before I go to someone else. I can drop projects off and pick up in person, which I like, as he's only about 45 minutes from my home.

[bigbear_98]

Well, after a week, there has been no reply from Satern, which is kind of what I expected, given my research here and in other places.

I've contacted the Pete Pieper, of Precision Barrelwork in Hempstead, Texas, who has done some great work for me before, to see if he has a reamer. He mainly does bolt-action benchrest and precision rifles, so I kind of doubt that he has a reamer on hand. But I always like to check with him first, before I go to someone else. I can drop projects off and pick up in person, which I like, as he's only about 45 minutes from my home.

I know Charles with Crowley machine has a reamer. He is in Taylor. He does great work. Everything I've had him do has been perfect.

[pinzgauer]

I've contacted the Pete Pieper, of Precision Barrelwork in Hempstead, Texas, who has done some great work for me before, to see if he has a reamer. He mainly does bolt-action benchrest and precision rifles, so I kind of doubt that he has a reamer on hand.

Personally, I'd only go with someone who has more than passing familiarity with Grendels and AR's. Ideally someone who has dealt with this exact issue before.

Bolt guns do not face the same issues. I know locals that I'd trust bolt guns to that I'd never take an AR to for anything more than basics I could do myself.

[therbert]

Well, it's a non-issue, because he doesn't have a reamer.

[alligator]

Also check the bolt face depth. They also sent some out of spec bolts too. If it is .130 it is incorrect. It should be .136. The bolt is right because they are made on brand new Swiss machines they said. Then they replaced it with a new-correct one.

[therbert]

OK, it's been a long time since I started this thread, and I just wanted to update it and thank everyone that responded and offered advice.

As I mentioned in an earlier response I sent an email to Satern, telling them about the situation, and politely asking them what, if anything they intended to do to fix it. I figured it wouldn't hurt, and could possibly help, if it stopped me from having to put more money into it. I didn't get an immediate response, and I forgot about it for a while. I sent the email to them somewhere around the 15th of November of last year. Around the middle of February of this year, I got a response from them (sorry, I can't give you a name, as I'm typing this at work, and all of that info is on my home computer) apologizing for the length of time it took them to reply to my email, and for the problem I was having with the barrel. They asked me to send them the barrel and bolt, and they would remedy the situation.

I got an email from UPS advising me that the shipment had been delivered on a Tuesday morning about 10:30 AM. I do remember that it was signed for by the same person that had responded to my email. At about 2:30 the same afternoon, I received another email from UPS advising me that I had a shipment on the way to me from Satern. When I got home that evening and looked at my email there, I had another response from the same person, telling me that the barrel and bolt had arrived, the bolt was checked and found to be in spec, that a chamber reamer for the new Grendel II spec had been used to update the chamber, the headspace had been rechecked, and that the barrel and bolt had been repacked and were back on the way to me.

The barrel and bolt arrived at my home three days later. The first thing I did was make a visual inspection of the chamber, and I could not detect that anything had been done to the barrel, which is a good thing. Then I took one of my reloads and slid it into the chamber, and pressed it all the way in with my thumb. When I up-ended the barrel, the round slid right out. I did the same thing with a factory round, and got the same result; no marks on the bullet from being forced into the rifling either, on both rounds.

I then reassembled the upper, and put it on the lower, and did a function check with the same rounds, allowing them to be stripped from a mag by the bolt, and slammed into the chamber. They both extracted with no problem.

I'm going to go sight-in and otherwise test the rifle tomorrow, and let you all know the results, but I don't really expect any problems.

I have to give credit where it's due. Although it took them a long while to respond initially, once they took the problem in hand, you cannot fault the remedy or the speed with which it was accomplished. Now all that remains is to see if the rifle groups well.