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6.5 Creed Swipes and Blown primers w/ +2 gas

smvmarine

smvmarine

Okie
Full Member
Minuteman
Oct 13, 2011
89
3
Central Oklahoma
#1
Ok guys I'm having a problem with my newly built 6.5 Creedmoor gasser. Little info on it, 22" Bartlein w/ +2 gas, SLR AGB, JP High Pressure Bolt, JP SCS Heavy. On my first string (3-5 rounds) of my range trip the last 2 times I have went I am getting a blown primer on one round on that string (assuming round #1). Also every round has slight swipe marks, this is on every round not just the first string of rounds. I am shooting Prime 6.5 Creedmoor. I built this with the +2 gas and JP HP bolt hoping to avoid this as I am planning on reloading. Thoughts?
 
#3
OP have you tried any other ammo? I wouldn't do anything until I tried some different ammo. If it happens with Hornady, Winchester and others, then you know it's your rifle.
 
#4
The balance of your components are right in line for controlling gas flow and BCG acceleration. Who cut chamber for you? Any chance chamber throat could be a bit short? Have you tried a std rifle buffer and a Tubb flat wire spring? And/Or Tubb CWS? Other brands or different bullet weights? Patience a pretty tough prescription to follow-it'll come around.
 
Last edited:
#5
Sounds like pressure could be the culprit. Are the non blown primers flattened? pics of brass?

Regardless; swipes and blown primers usually means pressure problems. Pics would tell a little more of the story.

If it is pressure you have 1 of 2 problems;

1.) The load is way to hot!
2.) The throat is cut to short.

Over pressure is dangerous. I would be weary shooting that thing any more tell you find the answer.

You need to find out at what seating depth the ogive of the bullet meets the rifling. They make tools for this. There are also less scientific methods for this as well....

If you don't have any reloading equipment or a set of calipers one method to see if you are jamming is to load a loaded round into the chamber and extract. If it's jamming extraction will feel harder to do then normal and when you examine the extracted cartridge if it is jamming you will "generally" see rifling marks around the ogive of the bullet from being jammed into the lands.


I've dealt with swipes, pierced primers, cratered primers, and a short throated barrel before. When reloading I've seen a range of swipes from light to heavy and cratered primers when the load is getting to hot.

On the 1 barrel I have had that was short throated I was only shooting factory ammo and didn't think much about the swipes and flattened primers tell I started piercing primers and damaged my bolt and firing pin from the hot glasses blasting rearward through the firing pin channel.

Don't be a dumbass like I have been. Check that shit out.




 
#6
I’ll gets some pics posted today, I’ve tried the Norma Ammo which was my break in ammo and it did the same thing. I’ve also got a some rounds from Cooper Creek using Alpha Munitions brass. These are getting primer swipes as well. If I remember right on break in I had a blown primer or 2 with the Norma. Craddock Precision cut my chamber. I’ve got a Hornady COAL gauge, I’ll measure today and post what length my chamber is cut to. Thanks!!
 
#7
Also, anyone know which factory match ammo is on the lighter end of the spectrum, I’ve read Prime 6.5 Creed is near the top end of the load, could be wrong but could have sworn I read that here on the hide somewhere.
 
#8
I've never pierced primers until I've run Prime ammo. In my bolt gun it was extremely hot. It was way too hot in the gas gun. Try a lighter load.
 
#10
It sounds like you have ammo too hot for your rifle. I am running an identical setup and I have zero blown primers, not a swipe or mark on my brass and its super soft shooting. PVA chambered my Bartlein 22" 6.5cm +2 gas barrel. Also, I am running the AR10 JP SCS with OEM spring. I bought the spring pack and tungsten weights it did not even need to install them. Tuned gas to lock back on mag.

I reload so cant really help with your Prime ammo issue but this rifle hammered with Hornady 140 Amax factory ammo which I used a 20rd box to tune the gas block.

Mega Billet Upper/lower
22" Bartlein 6.5cm +2 gas by Patriot Valley Arms
SLR .936 AGB
Rugged 3 Port 5/8-24 brake
SLR 15" Hanguard
JP LMOS w/High Pressure Bolt
JP SCS (Factory installed spring and weights)
Geissele SD-E
BAD Ambi Safety
BCM Charging Handle
Magpul PRS Gen3
 
#11
I run all jp internal parts and barrel. It shoots all the factory ammo i feed it unless I turn the gas block down to far. That includes a lot of the prime ammo and hornady American gunner which shoots surprisingly well. I would go with wild bill and say #2. Throat is to short.
 
#12
Youll want to grab a Hornady Overall length gauge and their 6.5cm modified case and find your distance to the lands.. I have some 130 Golden Targets which is what the Prime ammo your shooting uses. If you need me to send you 1 to find distance to the lands let me know. Or you can pull a bullet from your Prime ammo...Did they tell you what reamer they used? I would call them and see what they have to so.
 
#16
Can you stick a bullet into the fired case easily by hand? If not, the neck diameter of your chamber might be too small for the brass. Some guys are cutting chambers with minimal clearance for Hornady brass, which is the thinnest of them all, so thicker brass can give you issues like you describe.
 
#17
Also one thing I forgot to mention, on my first shot out of this gun (Norma 130gr)I had the gas turned down as I was starting low and gonna work my way up the brass got stuck in the chamber had a hell of a time getting my bolt pulled back to get the case out. Haven’t had that happen since that though.
 
#19
Left hand side is the Prime. Grouped rounds are from Copper Creek they get “hotter” from left to right. My OAL measured 2.835” with a 130gr Norma Golden Target. 2.832” with the Berger 130gr AR Hybrid which is what was shot out of the Alpha brass
 

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#20
smvmarine said:
Left hand side is the Prime. Grouped rounds are from Copper Creek they get “hotter” from left to right. My OAL measured 2.835” with a 130gr Norma Golden Target. 2.832” with the Berger 130gr AR Hybrid which is what was shot out of the Alpha brass
Click to expand...

My Seekins SP10, as well as did my JP, both in 6.5cm also had blown primers with Prime ammo. I just use reloads now.
 
#21
Ya, I went through the same thing in my carbine. It ended up being a timing issue. I went with SlashÂ’s heaviest buffer, The heaviest Sprinco spring, and the JP high pressure bolt and with SLR gas block. This setup totally resolved it for me. Not sure if it will work for you. But, best of luck...
 
#22
smvmarine said:
Left hand side is the Prime. Grouped rounds are from Copper Creek they get “hotter” from left to right. My OAL measured 2.835” with a 130gr Norma Golden Target. 2.832” with the Berger 130gr AR Hybrid which is what was shot out of the Alpha brass
Click to expand...

You are going to get some case head swipes with a large frame semi. Minimizing it with proper gas tuning and buffer weight/spring is key. Prime is known to be very hot and that is evident in the brass pics you posted above. The brass on the right (CC Alpha) likes normal for a semi. Your best bet is to handload if you really want to minimize those swipes. While the 140 Amax / ELD-M shoot great in my rifle, I get more swipe with them. The sweet spot is 123 Scenars, 130 AR Hybrids and 130 ELD-M's. I love the 130 ELD-M's because they are the cheapest of the bunch, have a good BC and are extremely accurate. Im also shooting Hornady brass which is thinner than the brass you are shooting. And if you had a case get stuck it sounds like your chamber was not cut with a reamer favoring a semi meaning its tight.
 
#23
I experienced this with 2 different rifles after installing 6.5 barrels. 1 or 2 out of 10 rounds would pop a primer. An experienced AR builder told me not to worry about it since the chambers measured correctly and there were no other pressure signs. He told me it would stop once the bolt wore in to fit the barrel - the lockup was not perfect? I was skeptical about it but they both stopped doing it after about 50 rounds of identical ammo. Maybe some other AR expert could expound on this since I really can't see this happening but it did seem to work. I do think the Prime 6.5 ammo is too hot for a gas gun.
 
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