Flatten, and pierced primers

[Warbone]

I have a DPMS LR308 SASS, bought a little over a year ago. Last summer i worked up a load for this rifle.
175g smk
Win brass
imr4064 43.9g
CCI BR2 primers
2.800 oal
i shot this load through half the summer, fall and winter. with no signs of over pressure and great accuracy.
However this spring, i have started to get flattened and pierced primers, as well as erattic accuracy.
I wondering if it may have something to do with the bolt carrier group, bolt ect.
Is the any signs to look for, like headspace, firing pin ect that might lead to to correting this problem.
I also use this same load in my tikka bolt rifle with no pressure signs.
Any info, or someone that might have encountered this problem would be very helpful.

 

[milo 2.0]

You're maybe developing a carbon ring in your barrel. Ar sytle guns sre notorious for this, it's usually right in the throat area. Try to feel for it while cleaning. You'll feel resistance. Soak a patch with a good solvent and let it rest in the spot, usually cleans it out.

 

[ChrisGarrett]

I'd get a jeweler's loop and look at the tip of my firing pin, if I were you.

You've probably blasted some craters into it.

Chris

 

[glassbeaver]

You're maybe developing a carbon ring in your barrel. Ar sytle guns sre notorious for this, it's usually right in the throat area. Try to feel for it while cleaning. You'll feel resistance. Soak a patch with a good solvent and let it rest in the spot, usually cleans it out.

This.............

 

[SWRichmond]

This is what JB is for.

 

[1lnbrdg]

All barrels build up the carbon in front of the throat area. That is probably biggest problem with barrels loosing accuracy, copper comes 2nd.

 

[Warbone]

Upon closer inspection of cases, i also have a ejector mark on the case head From the ejector in the bolt, i guess this might indicate a tight chamber/throat and since i didnt have any problems when the rife was new, i may have been lax in cleaning out the chamber throat area. Will have to check it out and report back.

 

[204 AR]

Did you change lot #'s of powder? Might have gotten a hotter lot.

 

[Warbone]

Cleaned Bolt, chamber/throat really well. Didnt fix the problem.
I have noticed on my brass when i resize it, check it on my bolt gun the bolt has some resistance closing, checked some older reloads and the bolt closes smothly. I tried adjusting my die, but i still get some resistance closing the bolt. I have probably run about 2000 round a brass through this die. How long will hornady FL reszing die last?

 

[Eznutz]

clean your die and make sure you are using enough case lube. My buddy was having the same issue and as soon as he added more case lube it solved the problem. Lube always helps.

 

[former naval person]

If you are using the ammo in a semi as well as the bolt, you probably need a small base sizing die. I doubt yolu have worn out die. With good lube the die will last for MANY years and thousands upon thousands of cycles. I suspect the difference in chambers is your culprit. I'd separate the semi cases from the bolt cases and size them to fit each gun.

 

[dogmessiah]

Your die isn't worn out unless you did something stupid to FUBR it. As for the sizing, how many loadings you have on the cases? You may need to anneal them to prevent spring back and get them to size down if they have work hardened to much.
As far as your overpressure issues I would suspect either a carbon ring or a change in powder lots as has been suggested.

 

[Deadshot2]

I find that my rifles leave an "ejector mark" (horseshoe shaped) on the case head when I've pushed the shoulder back too far. If you set your sizing die down to touching, then add the 1/4 turn many instructions call for, the cases can have more headspace than your rifle likes. I use a case gauge and set the sizing die so it pushes the shoulder back so the case head is JUST even with the highest surface on the gauge. I use the back of my caliper as a straight edge to make it easier to see that the head is just flush, no more.

It seems like whenever the case head hits the bolt face with a "running start" the ejector marks are more pronounced, all with the same powder load.

 

[Fuzzball]

"I have probably run about 2000 round a brass through this die. How long will hornady FL reszing die last? "

Normally something in excess of 150,000 rounds. Well, a Hornady or Lee may 'wear out' with only 145,000.

 

[Warbone]

Well i cleaned out the die and adjusted it somemore, was able to get the cases work good in my bolt gun. I have found that my tikka t3 scout and dpms lr308 sass have very similar chambers, and have found 4 loads that work awsome in both guns. I did find that the brass in the semi auto before adjusting was hard for me to manually eject, after ajustment it was alot easier to eject. Now to head to the range with my favorite load and see if its still show signs of over pressure

 

[Warbone]

Just a update, im still getting a little over pressure signs, about the only thing i can figure is Powder lot differnace, using 4064 i ran out of it in novemeber, i was unable to get more powder until just recently so i would have to be a new lot as all the other was bought up due to the mad rush we had.
If rifle was running just under pressure new powder from differant lot could have pushed it just over . Guess i may have to work up a seperate load for my 308ar.

 

[Deadshot2]

Just a update, im still getting a little over pressure signs, about the only thing i can figure is Powder lot differnace, using 4064 i ran out of it in novemeber, i was unable to get more powder until just recently so i would have to be a new lot as all the other was bought up due to the mad rush we had.
If rifle was running just under pressure new powder from differant lot could have pushed it just over . Guess i may have to work up a seperate load for my 308ar.

Just for grins, clean the dickens out of the chamber then "degrease" the chamber using a clean mop and some brakekleen. Also, make sure that no lube remains on your cases. Bolt thrust can cause the ejector marks. As for the primers, I shoot "Flat Primers" all the time. Softer material in a primer can cause it to flatten more than a different batch with no more real pressure in the chamber.