Over pressure?

[thumper3181]

I've had like three of these do this in the last 100 rounds and I am wondering is this a pressure issue or is something else going on. The primers are not flattened and bolt lift is normal, these are fired through a Ruger American Predator.
Load Data
Winchester 223Rem case
Winchester #41 SR primers
27.5grs of CFE223(27.8grs is Hodgdon's max)
Hornady 55gr SP
OAL is 2.220

 

[Benchrest Braxton]

is that a hole in the primer??

 

[thumper3181]

Yep, between the primer pocket and the primer.

 

[M-61]

Never saw that before.
Additionally I have to compliment Sigma on spotting that!

 

[Jeff Porter]

I had this happen with some Tula primers in a tube gun with a R-700 action. Had to have Walt Krafft re face the bolt. Same deal. Not a hot load

 

[acloco]

What primers are you using? Hopefully not Remington 6.5's.

 

[Benchrest Braxton]

Never saw that before.
Additionally I have to compliment Sigma on spotting that!

thank you sir, i never saw it before either. defect in the primer cups?

 

[Benchrest Braxton]

What primers are you using? Hopefully not Remington 6.5's.

he mentioned the primers in the OP, winchester 41’s

 

[M-61]

he mentioned the primers in the OP, winchester 41’s

Not only is your eyesight superb you actually read the OP
Congrats again!

 

[thumper3181]

What primers are you using? Hopefully not Remington 6.5's.

Winchester #41 SR primers

 

[Walt Krafft]

Oversize primer pockets?

 

[mac86951]

Three primers blown in the second picture; I'm thinking those primers have cup defect. Didn't Winchester have an issue like 5 yrs ago with their small rifle primers?

Could be excess primer pocket size or other process glitch in preparing the primer pocket? I'm not sure what would do that, I guess I should ask the OP, how did you prepare your brass / primer pocket and how do you seat primers?

-Mac

 

[thumper3181]

This is new Winchester brass and all I did was run it through a lee collet neck sizing die and deburred and chamfered the case mouth and worked up load data.

 

[thumper3181]

I use a Frankford arsenal hand priming tool.

 

[Bronsin]

Three primers blown in the second picture; I'm thinking those primers have cup defect. Didn't Winchester have an issue like 5 yrs ago with their small rifle primers?
-Mac

Yes they did. Fortunately none of mine had the affected lot numbers. Every one of those sooted primers in his photos have that pinhole.

 

[thumper3181]

Yes they did. Fortunately none of mine had the affected lot numbers. Every one of those sooted primers in his photos have that pinhole.

Yes, they do. These are their newer primers. I bought them from Midway last year I think.

 

[NZ_Fclass]

I would suggest running new brass through a full length die, not a collet.

 

[Ned Ludd]

Blown primers can sometimes happen in virgin brass because the brass hasn't yet expanded to fit the chamber and the base-to-shoulder dimension may be as much as .005" to .008" shorter than it will be after it has been fired. Loads don't necessarily need to be over-pressure for this phenomenon to occur, suggesting that little extra bit of clearance at the case head may be all it takes. It typically disappears as soon as the brass has been fire-formed and re-sized, even with no other changes whatsoever to the load.

I can imagine how something similar could be happening here. The virgin brass could be a few thousandths short (cartridge base-to-shoulder), allowing the primer to be pushed partway put of the pocket during the firing process. That slight movement could allow the pressure to escape via a narrow channel created in between the primer and primer pocket wall (i.e. the path of least resistance). If the gas is escaping between the primer and the primer pocket wall, it wouldn't necessarily be a "pierced" primer, meaning there may not be a hole through the primer cup. In fact, the damaged primers do appear to my eye to be noticeably flattened relative to those around them. This can be seen around the outer edge of the firing pin depression, which looks much sharper and less rounded than the other undamaged primers. There is no way to guess what might have happened just from the picture, but it looks like something might have caused an over-pressure situation in those cases.

Regardless, this phenomenon can etch the bolt face and potentially create a safety issue. You might consider dropping the charge weight even further until all the brass has been fire-formed. I might also consider using a primer with a harder/thicker cup until the fire-forming has been completed. I'd also have a look at the flash holes underneath the damaged primers and see if they look any different from the others.

 

[johnfred1965]

Looking at that box of brass, don't see how any pressure conclusion can be made. That box is a mix of rounded, flattened, and burned primers. If Ned is right about the headspace, your brass started out with several different base to shoulder lengths.

 

[DaveTooley]

Over the years every manufacturer has had this problem. It's a defect in the cups. I first saw it around 35 years ago with Federal 205's. A lot of damage was done to bolt faces of benchrest rifles then. As I said every manufacturer has had this problem. Stop using these primers and contact Winchester for replacements.