Primer Pocket Blow Out???

M

mram10

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Minuteman
Feb 8, 2010
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Idaho
#1
I reloaded some 300wsm. After shooting, I noticed that the primers were all flat. I also noticed on one case, that there was a blackened rip from the primer pocket. What exactly caused this? Just overpressure? Is any flattening of the primer bad, or is it only if it is accompanied by a sticky bolt?
IMG_2626.jpg

IMG_2627.jpg
 
#2
Re: Primer Pocket Blow Out???

That is a material failure. Doesn't happen often but there can be a thin spot on the edge of the primer cup that will fail and leak. Those cups are stamped out and formed. Sometimes the disc edge will have a slighty rough area that forms thinly when cupped leading to a leakage.
 
#3
Re: Primer Pocket Blow Out???

I agree, it's a material failure. The primer itself shows no signs of high pressure at all. That is not a 'flattened primer by any means. The edges all still have a very nice radius.

One of the things you'll more than likely see when you start to get too hot is the primer will have a "splash" around the firing pin indentation. That is the brass melting and flowing back. Another thing we're not seeing is case head rub. Even a not-so-sticky bolt will overcome a slight overpressure, and the head will come out shiny as it got set back too hard against the bolt face.

What do the rest of the cases look like?
 
#5
Re: Primer Pocket Blow Out???

I agree, no ejector swipe and the primer looks good except for the failure/leak.

Curious, what bullet, powder, and speeds are you loading to?
 
#7
Re: Primer Pocket Blow Out???

Defective primer cup, and it happens to all brands.

It's possible the shop or maker will replace that box/brick but when it happens to me I just religate that batch to low pressure loads (.30-30, .35 Rem, etc.) and get new ones for higher pressure loads.
 
#8
Re: Primer Pocket Blow Out???

Lets see, if all the other primers were flat, this one wasnt, but this one leaked like a muther, maybe you didnt get a flat one on this primer cause it leaked out a substantial amount of pressure? If the rest of the rounds were overpressure, I bet this one was too until the ass end of the case gave way. And the guys are right, you are going to etch that bolt face doing that.

Easy solution, back the load down a bit. :)
 
#10
Re: Primer Pocket Blow Out???

Those don't look bad to me. Primer flatness isn't the best metric in the world, but if you've got no ejector kick mark, no swipe, no primer cratering, and you've still got a radius on the corner of the primer, you're doing just fine in my opinion.
 
#12
Re: Primer Pocket Blow Out???

I had some Rem 7 ½ in a AR15 do same thing. I had 24gr of RE15 with Hornady 75hpbt. Pretty much a standard load in AR’s. To bad I bought a 1000. After a few blown primers I went and bough another 1000 (different lot#) and never had it happen again. I still have a lot of the other primers left. Man did they ever dimple the shit out of the bolt face.
 
#13
Re: Primer Pocket Blow Out???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mram10</div><div class="ubbcode-body">Do any of these look like primer flattening? </div></div>

The primers are taking on the first hints of flattening, but you are far from the point where the primers are showing excess pressure. You can see that the radius of the edge is reduced, but it is still present.
 
#14
Re: Primer Pocket Blow Out???

What Mudcat-NC said is exactly how to think as a reloader diagnosing problems.
That is likely why that round has a more generous primer radius than the others.

Were the primers Winchesters?
Win rifle primers are the worst I've encountered, their popularity is truly baffling to me.
They are inconsistent in ignition, and flatten and crater at lower pressures than other options.
Even the tougher primers still end up being the weakest link in the system.
Your primers do not all look the same, a good load will have fired primers that are all very similar in appearance.
It means that the internal ballistics may be differing from one shot to the next.

If, for whatever reason, you were able to seat primers too deeply into the primer pocket (>0.005") you could see these symptoms.
Are your primers deep within the pocket?
Over bumped shoulder for you chamber could cause this as well.
Ex:
The firing pin strikes the primer pushing the ammunition forward in the chamber (causing inconsistent ignition).
The primer ignites, blows-back within the pocket protruding beyond the case head until it contacts the bolt face (it could tear under these stresses). Internal case pressure begins to rise rapidly causing it to grip the walls of the pocket while the case moves rearward in the chamber until contacting the bolt face.
Because of it's death grip on the walls of the pocket, it smashes against the bolt face instead of pushing back into the pocket.

This can happen, even with low pressure loads.

If you come down 10%, and still see what you are seeing, this is likely what is happening.

If you are using WRP's you could see this, even if everything else is normal.

I do not believe that you are running excessive pressure based on the photos that you took.
 
#15
Re: Primer Pocket Blow Out???

Now that I see the primer in a direct looking angle it is as fuzzball said, and that is you have a defective primer cup. You can see the blowout on the corner where the rest of the cup is still radiused.

Once in a while everybody gets a bad primer or two. I think that is your problem here.

However, Hamilton pointed out you seem to have inconsistent results with all the primers. Specifically Pic one of your second group, second case from the left, on the top row. Make sure you are seating them to the correct depth. Also make sure you are not bumping the shoulder back too far and allowing the excessive headspace.
 
#16
Re: Primer Pocket Blow Out???

The info is appreciated Gentlemen. I use a standard lee priming tool. These were winchester primers. I bump the shoulder just a touch when resizing after firing. I use the neck sizer and run it down till it touches, then twist a touch more (.002~) so it chambers without a tight bolt. Is this correct?
 
#17
Re: Primer Pocket Blow Out???

I agree that it doesn't appear that you are pushing the load too far.
A few things, I prefer using CCI and Tula primers because have a harder cup. I see two different headstamps going on there, when you work up a load try to stick to one brand of brass, depending on the brass you use it could make a Big difference.
SScott
 
#18
Re: Primer Pocket Blow Out???

Blown primer at the skirt. Had the same thing happen with a batch of Federal 210M. If you have allot of the same batch of primers, contact Winchester for replacement. If you do not have many, trash them and drive on.

Good luck

Jerry
 
#19
Re: Primer Pocket Blow Out???

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mram10</div><div class="ubbcode-body">The info is appreciated Gentlemen. I use a standard lee priming tool. These were winchester primers. I bump the shoulder just a touch when resizing after firing. I use the neck sizer and run it down till it touches, then twist a touch more (.002~) so it chambers without a tight bolt. Is this correct? </div></div>

I'll bet I'm telling you stuff you already know, but getting a rifle to shoot well is like solving a puzzle.
I always want to start with what I know, and then attempt to solve for what I don't.

When you say "touches" are you referring to the case shoulder touching the chamber shoulder, or the die touching a shell holder or something else?

Without a case gauge you must use your chamber to set the bump.
It's good to have a supply of brass that does not want to chamber due to possessing excessive headspace.
That way you can keep resizing a donor piece until the bolt just begins to drop on it.
Then establish a range by resizing say two or three and attempting to close the bolt on them.
The donor piece will usually be harder after several resizes, and will spring back more, so if it fits tightly, the range of the others will usually be perfect.

Brass strains (elastic), and yields (deformation) differently depending on it's relative size, and hardness.
All I mean to say is that the brass will come out of the die within a range.
The more they differ in size, and/or hardness, the bigger the range will be.
Ideally they will all be within a headspace range of less than 0.005", and that range will overlap the saami spec headspace range perfectly, and fit your chamber perfectly.
This is hard to do unless the rifle was chambered by someone who gives a damn, and these folks are getting harder to find.

I like to be right on the edge of snug-fit, or slightly compressed for a bolt gun.

For reference:
One degree of rotation (7/8", 14 tpi) equals (almost exactly) 0.0002" vertical movement.
5 deg. rotation = one thousandths vertical movement.
 
#20
Re: Primer Pocket Blow Out???

Don't assume anything
smile.gif
I would rather hear it twice than not know it. I was referring to the die touching the shoulder. Then I would keep running it down till it fit in the chamber snug with the bolt needing just a bit of help coming down. I hunt in cold weather (I guess most do) and don't want the bolt to be too snug. I try and use the same lot of brass and shoot then the same number of times.

As for primers, it is the first I have seen blow out. I will keep an eye on these and return then if any more blow out.
 
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