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6.5 Creedmoor - Over Pressure with Factory Ammo

C

cfulback32

Private
Supporter
Full Member
Minuteman
Aug 11, 2010
134
9
Dallas, TX
#1
I went to the range this afternoon to shoot my new AR build. Components are:

22" Creedmoor barrel (from a big name maker, but I don't want to post their name for now. I want to give them a chance to get back to me first)
Mega Maten upper and lower
DPMS BCG
JP adjustable gas block
Surefire brake
Apex rifle length hanguard
Atlas bipod
Giessele SSA-E
H3 Buffer
Troy Buffer Tube
CTR Stock
Nightforce F1 Mil Mil
Nightforce Unimount 1.125" height

During assembly, the original bolt I bought didn't pass headspace test with the no go gauge. I bought 3 more bolts from Brownells. All 3 passed and were dimensionally identical as far as I could tell with calipers, so I just picked one and went with it.

Today at the range was the initial firing. Conditions were about 70 degrees with a light rain. No issues with the gas system. I started out at 2 turns from closed per JP's instructions. I turned it down about a quarter turn each shot until the bolt failed to lock on round 5. I cleaned the barrel in between each shot as well for these 5 shots.

The problem though is that I seem to be having some pretty visible over pressure signs on the brass, and the last 2 of the 5 shots popped out the primers.

I have emails out to the barrel maker and to Hornady. In the mean time, does anyone have any idea what would cause this? As far I can tell, it could just be hot ammo or something wrong with the chamber. As I mentioned above, headspace was checked and passed (closed on go gauge, won't close on no go gauge). I know there are other chamber dimensions that could be out of spec, but I am not too familiar with that.

After two popped primers I figured it was time to stop for the day and consult the more knowledgeable minds on the hide as well as the manufactures. Any input is appreciated. Thanks!

20120916_194101.jpg


This is at 50 yards. Round 1 was to the right. Scope correction was made and then rounds 2-4 are on top of each other. I wasn't on the gun for round 5 since I already had 1 popped primer at that point...

20120916_193445.jpg


20120916_181955.jpg


20120916_141857.jpg
 
#3
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

Gas was turned down for each round. Didn't lock back on round 5 out of 5. Both rounds 4 and 5 had the primer pop. The brass looked just as bad on those last 2 as well, so I'd say turning down the gas was no help.
 
#6
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

I had the exact same thing happen to me yesterday shooting factory 120 amaxes out of my GAP-10. I have never had issues before with this gun and factory ammo. Definitely the ammo is the problem for me.

With your's being a new build and not tested you might as well play it safe. Double check everything or take it to a smith just to make sure.
 
#7
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

how did you check for tight bore? i saw custom bolt gun with a top name barrel on it doing this. it was .002 under sized about 2" ahead of chamber. we sent barrel to maker & they sent a new barrel after they looked at it . tony
 
#8
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

I guess I thought the question was if it was ordered as a tight bore. It was not ordered that way, but I have not verified anything other than headspace.
 
#9
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

I know they did have some hot 120gr ammo as mentioned but have not heard anything on 140's I would for sure be checking your chamber.

Have you fired any other Hornady ammo? Do you reload?
 
#10
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

If you reload, have you measured the max OAL? If not, measure a factory round, chamber it, then re-measure. My 6.5 Creedmoor was cut with a very short throat. It was jamming the factory 140's pretty badly, but I didn't notice because there is not much neck tension. I found out pretty quickly with my handloads what the problem was.
 
#11
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

what i meant are you using factory hornady 140 a max or the hornady superformance/ I had an issue with the superformance . hornady said they are only rated for bolt guns
 
#14
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

The super performance does have some issues with gas guns although it works fine in mine with just a faint ejector swipe. I definitely look forward to hearing what the end result is here.
 
#15
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

I was just going to say chamber issue. I have a Tubb 2K and have pressure issues with my Palma load. Lapua brass after two reloads and the primer pockets are shot....and I'm one full grain below the "accepted" Palma load.

I know that this isn't a T2K thread, but I have had brass that looked like that from pressure issues originating from a chamber problem.
 
#17
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

From what I have read there should not be a problem using the factory 140 in gas guns. There seem to be lots of reports of issues with super performance in gas guns though.
 
#18
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ddavis</div><div class="ubbcode-body">If you reload, have you measured the max OAL? If not, measure a factory round, chamber it, then re-measure. My 6.5 Creedmoor was cut with a very short throat. It was jamming the factory 140's pretty badly, but I didn't notice because there is not much neck tension. I found out pretty quickly with my handloads what the problem was. </div></div>

What barrel Are you using ddavis?

Cfulback, I would check this. Even though it should shoot factory ammo.
 
#19
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

Should I be concerned with any damage to the bolt from this? I would have to imagine the pressure spike can't be good for it. I'm wondering if it would be reasonable to ask for a new bolt if it turns out to be a chamber issue.
 
#21
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

Was all the ammo from the same box? Are all your boxes from the same lot? I saw on 65creedmoor there was a guy that had 1 box that was too hot. He had other ammo from the same lot that was ok
 
#22
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

Your throat length is probably too short.

Smoke a bullet (or mark it w/ a sharpie) and chamber it, then remove it and see if it has rifling marks on the bullet.

If so, you will either need to handload or have a gunsmith lengthen the throat.
 
#24
Re: 6.5 Creedmoor - Over Pressure with Factory Ammo

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Hellbender</div><div class="ubbcode-body">Your throat length is probably too short.

Smoke a bullet (or mark it w/ a sharpie) and chamber it, then remove it and see if it has rifling marks on the bullet.

If so, you will either need to handload or have a gunsmith lengthen the throat. </div></div>

Good idea. Just gave that a shot, but there are no marks on the bullet.

I've reached out to the barrel maker and who I bought the barrel from and I'll be having them take a look at everything at this point.
 
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