Primer backing out on factory ammo?

[slicksleeve]

Friends, I just shot a Turkish K kale, in 8mm today. I've had it for about a month. The bore was in awful condition, I bought it with the intention of a rebarrel project. I gave the bore a good cleaning last night. Anyhow, when I shot it, the first shot was a misfire. I then took the bolt down and reassembled it, which resulted in a good strike on the primer and the cartridge fired. (The inside of the bolt was pretty gunky). The ammo is 8mm Remington 170 grain Core-Lokt factory ammo. After ejecting the cartridge, I noticed that primer had moved backward out of the caseing. One primer moved out about .010", and the other about .004. I've never seen any of my handloads or factory ammo do this. I suspect it is the rifle as I have fired most of this ammo in my other 8mm mauser and it hasn't done this. The bore was clear of obstruction, I even pulled out the bolt and looked at the target through the barrel before firing it. So, what is my problem, or did I possibly screw it up myself? Can I fix this, or do I need to shelf this rifle as unsafe? You might not can tell in the picture, but I put one here anyway.

 

[Waywatcher]

I'm no expert but it sounds like excessive headspace.

 

[KosmicKrunch]

Slicksleeve & Waywather: yes, most likely headspace, about an $85 fix if the set back is not too bad. If it needs a new barrel, just add the cost of the barrel.

 

[slicksleeve]

Thanks guys, I probably will rebarrel it anyway. That's what I had in mind when I bought it. I asked my maw-in-law for an action wrench for christmas.

 

[triggerman770]

headspace

what you are finding is: shooting American ammo made to SAAMI specs in a gun headspaced for CIP spec'd ammo. Just went theu this in the oposite.
a Douglas Barrel headspaced for SAAMI Ammo and shooting CIP spec'd ammo in it
tryh shooting some european ammo to see if the primer backs out. If it does too it's a headspace problem, to which you can have it headspaced either way SAAMI or CIP

 

[Jim K]

It is a combination of excess headspace and low pressure. Here is what happens:

When the round is chambered, the extractor will be holding it back. When the gun is fired, the firing pin drives the round forward, firing the primer at the same time. The primer backs out as far as it can from its own internal pressure (the powder charge has not yet fired). Normally, the excess headspace would result in the case stretching and then backing out and forcing itself over the primer, but for some reason, the pressure was not high enough to do that. Not only are American 8mm loads low pressure to begin with, but I suspect that the barrel is so bad the bullet is not even sealing the bore and the pressure remains low. So the case does not back up.

In short, that rifle is in very bad shape. If you want to rebarrel it, I suggest doing so ASAP and set the headspace up properly.

Jim