Savage 10 .308 win, blown primer

M

mikejonestkd

New member
Good day all,

I blew a primer today and need assistance in determining what happened

Rifle: Savage 10 FCP in 308, all stock except a new trigger. it has approx. 150 total rounds though it in the past 6 months.

Load date
.308 Win Lapua brass, fired once before in the same rifle. This load was neck sized only.
168 gr TSMK
44.0 gr IMR 4064
Win primers
2.800" COAL
Velocity is mild - 2640 FPS average

I had put 20 rounds though the rifle today over the course of about an hour and it was shooting well. However the temp was over 90 degrees and the barrel was heating up fairly fast. It was definitely on the warm side when I chambered the round that blew.

The round that blew the primer chambered fine with no difference between it and previous rounds. I noticed no difference when firing either, and the bullet went where I sent it.

I went to eject the round, but it was stuck in the chamber, and the primer fell into the magazine well. A quick push with a cleaning rod got the brass out of the chamber easily, and then I noticed that the extractor had slipped off the ball detent on the bolt face. This probably explains why the round did not eject. I easily reset the extractor on the ball detent, and it now works 100%.

So, what happened? The load is on the mild side, the rifle and brass are new and good quality, so this should not have happened.

Is it possible that the extractor failed before firing the round, and the cartridge was not firmly against the bolt face when I fired it?

Any insight would be greatly appreciated.
 
That load was popular back when 308's were popular in some competition events. Normally a safe maximum load.

Normally, all case heads are pressed very hard against the bolt face when fired after pressure has peeled.

Something was different in your situation. Pictures of case and primer would help.
 
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43.4 is maximum in Sierras load map , using the 168 gr hpbt match bullet at 2.800" col.
The TMK tipped bullet shank will be deeper into the case.

Sierra is using Federal brass. If you brass has less volume & is heavier, the powder charge should be reduced.

The high temperature didnt help.

If primer pockets become loose in 5 firings or less, reduce the powder charge.


http://bulletin.accurateshooter.com/2016/06/sierra-matchking-smk-vs-sierra-tipped-match-king-tmk/
Sierra MatchKing (SMK) vs. Sierra Tipped MatchKing (TMK)
 
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A quick update, as anyone would have guessed, I was over pressure.

I was seating the Sierra TMK to the same COAL as a traditional MK, and they were too deep in the case. The high temp was icing on the cake for my mini disaster.

I tumbled, sized, and reloaded the same 20 pieces of brass, reducing the charge to 43 grains, and seating the TMK out farther.

I shot again today under almost identical conditions- it was 92 degrees in the shade today! 20 rounds downrange in about an hour.
Velocity was almost identical- 2630 fps, and accuracy was as expected. no pressure issues.
 
I had some issues with Winchester primers in the past with nearly starting load pressures. Ruptured along the radius of the primer, multiple primers from that lot. I believe there was a recall, but it has been years ago.
 
Amflyer, I recently read a bit online about some problems people were having with Win rifle primers.
As soon as this pandemic shortage is over I plan on switching to another brand.
 
I was getting pierced primer cups a few years ago with Win LR primers. They were piercing at the edge of the primer adjacent to the primer pocket. The primers were defective. Apparently, the cups were too thin.

Upon discovering the issue, I contacted Win Ammunition CS. The CS rep was aware of the problem and was very helpful. I had an unopened case of 5K on top of a few hundred more. The CS rep bought them back for more than what I'd paid for them and arranged for shipping. Win was fair.

I purchased those primers in or about 2014.

In addition to the primer cups piercing, the escaping gases can, and will, scar the bolt face.

Bayou
 
Post #4, the OP solved his issue, excess pressure.


I’ve never had a problem with Winchester primers, but then any mass produced item can have QA issues.

I never had a heart attack, until I did.



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