Pin Hole In Primer

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gahunter12

gahunter12

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I'm at the range today running some 7mm Rem Mag loads across the chrono. This is from a Once fired case that was fired in my rifle new. The load is as follows

FC Brass
Federal Mag LRP
68gr of Retumbo
160gr Sierra GK BTSP

What do you think could have caused this? I hand prime all my rifle brass, and weigh each charge. This one has me puzzled since it's true once fired

88A83D66-D35D-437A-8D27-E7086ED0DEA3.jpg
 
Yes it does. I am starting to re-think using this FC brass. The primers have worked fine in my 300wm loads, but this is a first. Do you think the bolt will be trash?
 
When seating the primers, did they go in extremely easy?
I'm guessing worn out primer pocket and gas leaking like 243winxb said.

Federal is known to have loose primer pockets. I use plenty of FC brass and haven't had your issue, but I have noticed the primers generally seat with much less effort. I don't shoot max loads so I've never completely worn one out.

It is troubling to see it happen on the first reload.
 
Has to be either too much pressure, or a weak spot in the primer cup. It's not just gas leaking around a primer in a loose primer pocket. It may be loose, but it wouldn't cause that.
 
I'm sure the bolt it fine. Pop enough primers and it would be ruined, but IMHO, it would take a lot.

Look closely and you'll see a divot or two in the below.

8-20-12009.gif
 
Has to be either too much pressure, or a weak spot in the primer cup. It's not just gas leaking around a primer in a loose primer pocket. It may be loose, but it wouldn't cause that.
Click to expand...

Take a needle and see if the hole goes inside the primer cup.
 
Why would the bolt be trashed if there was a pock mark on the bolt face? Just a question...

Nevermind. Answered above.
 
Has to be either too much pressure, or a weak spot in the primer cup. It's not just gas leaking around a primer in a loose primer pocket. It may be loose, but it wouldn't cause that.
Click to expand...

You are right about the hole being in the primer. The pockets seemed to be fine when seating. I had to really hunker down to full seat the primer. My velocities are at 2830fps av.
 
Why would the bolt be trashed if there was a pock mark on the bolt face? Just a question...
Click to expand...

A while back a guy posted a picture of his bolt in a reloading forum somewhere. The bolt looked like it had a moat dug around the firing pin hole. :eek:
 
Bolt ok with pocks. Your load seems ok. Strange for once fired brass. Common to blame FC brass as soft. Its possibe to get 1 bad primer in 1000. But if its a manufacturing defect, your likely to get more. My old/sold M16 bolt face.
th_M16A1Bolt.jpg
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Yeah, looking at it the second time the hole is in the primer itself. The case is sooty from the escaping gases but doesn't really look damaged.

I didn't think a loose primer pocket would blow a small hole in a primer but wasn't sure.
 
I had one more about 10 shots later that appears to be in the primer as we'll. I am on my way home now. When I get home I will clean the cases up, and take a closer look. I have used 350 primers out of this box of 1k Federal Mag LRP. Till today they have been flawless. I also shot 30 rounds in my 300wm without issue.
 
I ran across this last year with RP brass in 45acp. I was shooting mixed head stamp and it was only related to RP brass. Which I relate to the way RP over cut the primer pocket, even though this is first time I had problem with them. I have since quit using RP brass with this mfg of primers. The mfg took all the primers I had left back and replaced them 2+ for 1 for my trouble. The odd thing is that I have been shooting the same load for 3 yrs when this happen.

I would suggest you contact federal on your primers, have your lot number ready. My guess is that they will want them back. Most will send you a 2 for 1 for your trouble and will cover cost of repair if it did damage to your gun.
 
I've blown a few primers in 7mm RM, and a few other cartridges before, and they usually look something like that. My guess is your load is on the cusp, and that particular piece of brass or the primer, couldn't contain the pressures, and then it just let go. That load is by no means a powder puff, it's definitely up near max, so your going to very likely see a few of those from time to time when loading up near the top like that.

As for your bolt, unless you do this all the time, it should be fine. As I stated up top, I've blown my share of primers, and the bolts are still OK. But when I blow more than one with a particular load, I know I've probably reached max, so I back it down a smidge.

GS
 
My guess would be a stress crack in the drawing of the primer cup that escaped the inspection process. Probably a mechanical flaw or hardness of the brass coil raw material. Just like the rare splits in case necks or walls that show up in new or once fired brass.
 
Ok here's some pics I took after cleaning the cases up, and after I de-primed. I am aware that 69.5gr is max per Hodgdon's site, but this really caught me off guard when my go to load has been 70gr of Retumbo for years. This was a load work up for a 7mm I acquired recently. This has truly been a first for me. I worked up to 70gr today without fail at 70gr, and no sticky bolt what so ever.

FD9415A5-E759-4BE7-BD5A-6163B27A48CF.jpg

2440F3B9-1DC2-4AB4-8991-CBB3A134033A.jpg
 
I noticed in the pic of the primed case it looks like there's a ridge at the edge of the primer. Could I be seating my primers too much? They are pretty darn tight going in, and after I seat them I squeeze a little harder where my handle bottoms out.
 
Here's a pic of my cases @ 70gr of Retumbo. The primers are flat, but don't appear to be flowing, and the bolt was not sticky at all. This has always been my load since it's were my other 7mm drives tacs at 3,000fps.

B18A9CD6-AA06-45EF-8199-E98F1E0042D3.jpg
 
Ok.

You can see on those primers that they are near to bursting through at various points.

It's so regular, and so precise on each primer it makes me wonder if you have some sort of existing damage/manufacturing defect to your boltface thats making/enabling this happen.

If you had a bad lot of primers, that had a bad stamped cup ( like they had a flaw on the inside) that might explain it too- and it'd more than likely be the same all through the lot.

The type of hole you have thats eaten through the primer in the examples given is in exactly the same spot on your retumbo loads- but that apparently wasn't hot enough to bore all the way through.

Thanks for the pic of the primer seater face- but I don't think thats our issue. Maybe.... we have to look at everything.

Maybe you have a new lot of hotter retumbo ?

Maybe the boltface damage/imperfection is deep enough that its allowing the primers to blowout at lighter loads on your new rifle, as to your old rifle ?

We need pics of your boltface- but very clear ones !

I'll stay online as long as I can, but the office wraps in about an hour, and then its about an hour drive home !

I'll also note that you have a hornady case there, and several FC's- someone will bring this up, I'm certain- but all of your now blowouts are on FC's, too.

Got any of these FC primers not yet seated ?

Maybe we can pick one apart and look for defects on the inside.
 
Last edited:
Here's a pic of a few cases before the primers blew. The bolt face didn't have any damage at all until the primer blew. This gun was practical brand new with no damage or erosion at all until the primer blew.

26685350-41BF-452A-856A-4D794E6D2F63.jpg
 
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