Blown Primers

[chuckshoots]

I was just out sighting in a Blaser S2 double barrel 308 and noticed that the primers were flat but fired a few more to make sure it wasnt a weak firing pin or something. Out of 8 rounds fired I had 2 primers blown out and all had very flat primer marks.
I had used the first half of the box of Hornady Superformance 150gr GMX in shooting a Rem700 SPStac with no issues and normal primer dimples.

So basically, I am wondering what the causes might be, as this is factory ammo could the chamber not be to spec? Or could snow have gotten into the chamber or on the cartridge to cause excessive pressures...it was/is snowing rather hard.

thanks for the help. I will try and get a picture up of the cases.

[SKSDan]

There's alot of things that could cause it. Flat primers is a pressure sign. Polishing the tip of your firing pin may help because if there's a burr its more likely to blow

[Noonanda]

Winchester had a bad batch of LR primers a while ago, I had them blowing out on me on the edge of the Cup.

[russt]

Check the headspace, you might have to little.

[Ahhnother8]

One drop of water or snowflake can cause excessive pressure. Steam is an amazing source of energy.

[ferretwithacheeseknife]

What do the cases look like?

Do they chamber hard?

Is the gun chambered for .308 Winchester?

You are running pretty high pressure if you are blowing primers.

[Dutch3]

I have had a couple blow out on me recently. Light loads, but both WLR from the same lot.

[JagerDog]

Check the headspace, you might have to little.

Being GMX, freebore could come into play too. I know Barnes likes a little bullet jump. GMX is "supposed" to load like regular Hornady, but....????????

[arnie19]

That picture looks just like the pictures i have seen of bad Winchester primers .They blow a tiny hole right at the curve of the cup .This will ruin your bolt head if it continues . Arnie

[Bill Steele]

It is difficult to say with certainty, too many variables. I think my money would be placed on Ahhnother8's analysis. Liquids don't compress easily and if you get something between the neck and the throat, pressures can go off the chart.

That is why we remove sizing lube, why you want to remove any grease or gun oil in the chamber and throat before shooting, and why we trim brass after F/L sizing, to assure the case neck doesn't jam in the throat and inhibit the neck expansion that releases the bullet.

Maybe try a different brand of ammo on a dry day, process of elimination.

[J-cat]

Winchester had a bad batch of LR primers a while ago, I had them blowing out on me on the edge of the Cup.

Can you tell us the lot number?

[SandDiegoDuner]

I also had a Winchester large rifle primer do that. I have a couple thousand that are the same lot. I will post the numbers I have when I get home. Anyone else have luck getting these replaced?

The one primer that did that left a nasty burnt carbon mark on my 1903A3's bolt face. I would like to keep in the nice condition it is in without any further damage.

[Bill Steele]

The problems with Winchester primers have been happening for many years, both in LR and LP. I have never heard a single case where Winchester didn't replace the lot of someone who has experienced these failures. They have happened with many, many, many "lots".

[chuckshoots]

Hey guys, here is a picture of the primers


The top 2 were from the Rem700SPSTac, from the same box of hornady ammo, that were shot a few minutes before.
Middle two were from the Blaser, where the primers are definitely flat, but the primers are of course not blown out, and the bottom two had their primers blown out, one of which I found.

I believe it would be frmo the snow, the wind/snow was coming from behind me and with the bolt gun shooting prior, the snow/wind was unable to get access to the chamber, while with the Blaser breakaction was opened up to the snow. I think that must be the case. The Blaser is definitely a 308 win. The cartridge definitely chambers easily and normally.

I will try some of the same ammo, as well as some different ammo when its no longer snowing and wet.

thanks guys

[LynnJr]

The top two are showing cratering which is common on 700's with sloppy/oversized firing pins in them.
Greg Tannel at Gre-Tan Rifles fixes the bolt and pin for around $70 within 1 weeks time.

On the rest the first thing I'd do is clean your barrel real well.If you build up alot of carbon in the throat you see that.

There are a bunch of other possibilities as well.