Alright... what would cause this?

ipscgraz

ipscgraz

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Got my shortened M14S to the range today, for it's second day at the range.

Fired a half dozen rounds fine, then "click" when it should have gone " boom"
This is similar to the first firing a month or so ago.

I eject the round and look at the primer; good hit but the primer is raised out of the primer pocket in the case by about 1/32".

Curse myself for poor loading practices but I was sure I had all the primers seated.

I watch the next round & it's primer...all good and fires fine.

The next round is a misfire and the primer is again hit hard but the primer is also raised not quite the 1/32" of the previous round.

Seems like when the barrel gets hot I have this problem...

This is 7.62 brass but loaded with .308 dies...hmmm.

Pic 1: Rifle with barrel shortened

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Pic 2: primers before firing

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Pic 3: Primers after misfire....hard to see but several are proud of the primer pocket.

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Pic 4: Primers OK on the rounds that fired successfully.

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Anybody got any good ideas?

SORRY FOR THE SCREWUP WITH PICS...HAD A CALLOUT RIGHT WHEN POSTING.
 
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Sounds a little like the primer ignited and jumped it out a little. As it jumped out of the pocket.. fire did not go through your primer hole because it jumped out and left too big of a gap. The primer should be prevented from moving on ignition by the boltface. It primer jumped out.... bolt face was not there against the primer... means headspace may be wrong. You had the gun rebarrelled? Did you check the headspace? Do you have access to a Go-No-Go gauge? Is barrel a half screw too loose?
 
Pull the bullet and investigate. Find out whether those primers actually ignited or not. If a primer alone goes off and there is no powder burn, at least with pistol cartridges, you end up with primers sliding out of the pocket slightly.
 
7.62 Lake City 63 brass...have a lot of this and never had any problems up to now.

Other than the shortening job (which should have no effect) I never touched the barrel; I checked headspace at one of 45ACPking's clinics but yes, I want to check it again.

Will pull the bullets and investigate; I don't think the primers fired at all.

However, the fact that the primer has such a strong impression from the firing pin indicates to me that the chamber isn't oversize...the case had to be pushed fully forward in the chamber for the firing pin to hit it that cleanly.

I will try a different batch of primers on the same brass and see how that goes.

Thanks for all your suggestions.

More to follow

BG
 
I had a similar problem when I chopped mine, although mine would occasionally short stroke and an occasional primer woud move back. I was told to try just necksizing my brass and keep that batch of brass for that gun. That's what I did and haven't had a problem since. I knew my headspacing was on the large side of the tolerance and have been actively looking for a usgi bolt, but this works and haven't had any issues.
 
What load? Primers backing out is a sign of excess pressure. Did your reduce the load by 10%? Milsurp brass is a bit thicker than commercial and the load must be reduced due to the slightly smaller case capacity.
 
Just a thought.- did you tumble clean those cases. If the flash hole was plugged the flame could not ignite the powder but pressure could be generated in the pocket itself backing the primer out slighty. Tumbler media blocking flash holes is common. Check to see if the primers have ignited.
 
The real problem is squib loads.

I made a squib using kitty litter as powder. Guess what. A partially backed out primer occured upon firing. Interesting, who would have thought that would happen. Not me.

I wonder if one could measure head space from this phenomenon?

How old is the powder you are using?
 
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ipscgraz said:
from the sound when I tried to fire I don't think it did...
Click to expand...

My squib did not sound as if it went off either. It did!

The kitty litter was compressed to the point that a pick will be required to remove it from the casing.

A primer has more energy than we give it credit for.
 
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I have been pondering this thread and i can't see any reason the rifle itself would cause this problem. I'm gonna lean towards agreeing with some of these guys that are indicating a problem with the cartridge and it's components... but with that said, I specialize in the rifles..... and am not by any means a specialist in reloading so will leave those diagnoses to others
 
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