There I was...

Ammunition, reloading, shooting, etc
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Culpeper
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There I was...

Post by Culpeper »

I took one of the K31s out for a spin today. It wasn't too bad on one hand but a disaster on the other. The brass was RUAG boxer primed. The load came out of the Siierra book. It is a great rifle but I apparently fed it a hot load. Primers were blowing out and a causal observer would say they were flattened. HOOBOY.

So it is back to the drawing board.
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madsenshooter
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Re: There I was...

Post by madsenshooter »

It's pretty common with the K31 to accidentally stuff the bullet into the nigh nonexistant throat. I went with bullets that are of a secant ogive design. The Sierra Tipped Matchkings can be seated out to max magazine length but tangent ogive bullets like Nosler Custom Competitions or regular Matchkings have to be seated much deeper. You shouldn't be over pressure with that charge weight. I run 46.4 of 4064 with the 168gr Tipped Matchkings or the PRVI 168gr match bullets. The PRVI bullets are very tapered and can also be seated out long. The internal capacity of a Graf or PPU case that has blown out into the K31 chamber is nearly the same as LC67 30-06 brass, incidentally. I also use that 46.4gr under a 168 in my Garand. A start load according to Hodgdon's site. Is that the Sierra 1st Edition? Can't find mine right now, the notebook style. They were being super cautious as I recall.

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butlersrangers
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Re: There I was...

Post by butlersrangers »

Was your RUAG brass originally 'pocketed' for Berdan Primers and then adapted somehow to accept Boxer Primers?

Possibly the RUAG primer pockets are not gripping the primers with normal 'friction and tension'?

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Culpeper
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Re: There I was...

Post by Culpeper »

The brass acted normal when I was priming them. I was getting resistance like I would with .30-06 or .30-40. I scrapped those twenty pieces and will recreate the experiment later this week when I am off the road from San Antonio.

Here is a pic of the head stamp
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butlersrangers
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Re: There I was...

Post by butlersrangers »

I didn't know the Swiss were making Brass with pockets for Boxer Primers.

trapdoor4570
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Re: There I was...

Post by trapdoor4570 »

My 2 cents.
I do not think you have a problem with over pressure.
There is quite a dance that goes on when the primer goes off. The pressure in the primer pocket shoots up before the powder ignites, the pressure forces the primer to the rear as if it were a piston and the pressure on the front of the primer pocket tries to push the case forward. Yes it is measured in microseconds not milliseconds but it does happen. As the chamber pressure comes up the case thrusts to the bolt face reseating the primer but if the primer has started to expand it may not fully reseat especially if the primer pocket has very little radius as your example shows. If the primer has mushroomed enough to not reseat the primer can prevent the base of the case from contacting the bolt face and the primer will transmit most if not all the pressure to the bolt face.
I have this problem, it is very common in my ‘03’s and the 40x 7.62 NATO using 15 to 18 grains 5744 or IMR 4227 with the U-311291 cast bullet. Some times when I look at a fired case I wonder how the gun survived, the primer has transmitted all the pressure to the bolt face. I just micked one spent primer it measured .215” on a .210” Boxer. When there is case blowby from low pressure you know the pressure is low and the case over time maybe under minimum headspace length, causing this to happen more often. As long as the groups stay around 1” or less at 100 yards I’m not going to worry about under size cases but I won’t use the cases for full power loads.
A much better way to gauge if the pressure is too high is to look at the case expansion at the web area if the expansion at the web looks normal the load probably is OK. If the expansion is further back than before you may want to rethink the load. Your load is in line with published loads I have checked.

If you wish to test this theory I suggest an experiment. With a ’98 or an ’03 remove the extractor and take one case full length resize and prime. Drop the case in the action, hold the gun vertically with the muzzle down and fire. Push the case out with a cleaning rod manually knock the primer out and re-prime. Repeat again. What usually happens is that after 12 to 15 times it will not fire because the firing pin cannot reach the primer.
In the ‘60’s our club was issued, for the DCM matches, M1 Garand’s and surplus Korean War era M2 ball ammo loaded with ball powder and a very strong crimp. The first time we tried this new lot of ammo everything came to a screeching halt, the ammo was way over pressure. The primers were unbelievably flattened. After a little investigating we were back firing in an hour. The cause? The primers had backed out and were unable to reseat because of the strong crimp, the primer were sticking out far enough that they were higher than the base of the case and the primer was transmitting al the thrust to the bolt.

Doubly Reincarnated
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Re: There I was...

Post by Doubly Reincarnated »

What is the diameter of the primer pockets in both fired and unfired cases?

FredC
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Re: There I was...

Post by FredC »

Culpeper wrote: Sun Jan 29, 2023 2:29 pm I scrapped those twenty pieces and will recreate the experiment later this week when I am off the road from San Antonio.
Honk the horn when you drive by Dewees.

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psteinmayer
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Re: There I was...

Post by psteinmayer »

FWIW, I'll add my two cents in on the 7.5x55 discussion:

I've been using actual Swiss Army (pun intended) GP-11 brass. Yes, this IS Berdan primed and I am using Tul-Ammo KV7.62N primers (I got lots of 'em). I load them with 40.0 grains of H4895 and a Nosler Custom Competition .308 dia HPBT... same bullet I use in my Garand reloads. My loads are within the normal range and perform well.

Now... here's the interesting bit: If I seat the bullet out a hair too long, they will engage the throat and actually prevent the bolt from going into battery... discovered by the "Click" and lack of a "Bang!" It IS possible to circumvent this by actually slamming the bolt handle... but having this happen during a rapid-fire string in the Vintage Rifle match at Camp Perry tends to throw one into a serious panic! This happened with 5 of my 8 rounds during the 2019 Vintage Match! I even had one pull the bullet out of the case during extraction... again, during Rapid!!! Enough about that. Now, as for primers, my primers (remember, they are Berdan) have never blown out... but are routinely what I would describe as slightly flattened. I've never seen any other indications of excessive pressure and attribute this to thin primer cup material and the "slightly flattened" primers are always uniform.

madsenshooter
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Re: There I was...

Post by madsenshooter »

That is a very big flash hole in those cases. I've experimented some with changing the diameter of flash holes, bigger ones do cause more primer flattening with all other variables the same.

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