Primers backing out

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jim18611865
Posts: 100
Joined: Thu May 15, 2014 9:16 pm

Primers backing out

Post by jim18611865 »

My son and I had a great time last Thursday since the club just opened back up.
When I got home I noticed the empties of some of my .32 Remingtons were backing out.
There were plenty of threads in the forums about this. Is this just the nature of the semi auto beast?
I couldn't take the recoil anymore, so I let my son shoot an original factory box. They all worked, but even some of those primers backed out.
Of the factory Remingtons 6 of 20 primers backed out.
Of my reloads, 4 of 21 backed out.
I did measure from the base of the shell to the skinniest part of the shoulder.
All the shells with primers backing out were shorter. 1.537-1.548 (backing out) vs. 1.550-1.568 (not backing out).

Has everyone who doesn't reload observed their empties?

Thanks for any comments.

Jim

Fred
Posts: 134
Joined: Wed Feb 26, 2014 11:10 pm

Re: Primers backing out

Post by Fred »

Posted this in another primer-related thread here, but yes, I've observed the primers backing out some.

Image

It's 2 different .35 Remington M81 barrels shooting the same 200gr Factory Remington Corelocts from a box of 20. One has a 'tighter' chamber than the other (foreground vs background). Since the cartridge is low-pressure the case is not stretched to put the head against the bolt face, but there's sufficient pressure to push the primer back.

If you reload those cases, be sure not to size them to excess. Depending on how your dies compare to your chamber, you only need to bump the shoulder back .0015" to -.002" to have reliable ammunition. Any more than that you're just stretching the brass and will likely get reduced brass life.

You can probably use a pair of calipers and a backward spent/deprimed .40 S&W case to measure headspace of your fired cases. Find the longest one and size everything to that or .0015" less.

jim18611865
Posts: 100
Joined: Thu May 15, 2014 9:16 pm

Re: Primers backing out

Post by jim18611865 »

When you say "bump the shoulder back" are you saying to not let the die go too far when resizing?
I have seen this mentioned several times, and am not 100% sure what it means.

This is the only bottle necked case I load for so I have no reference other than straight walled cases where I go almost all the way down when resizing. I did notice on the 32 that there was no way the die was going that far. I went until it got to difficult and called it good. Ammo cycles fine. I am using 3031 at 31.5 gns. Next batch I am bumping it up to 31.8. 170 gn. Sierra bullets.

Thanks, I appreciate the feedback.

Jim

Fred
Posts: 134
Joined: Wed Feb 26, 2014 11:10 pm

Re: Primers backing out

Post by Fred »

Yes, bottle-necked cases typically headspace on the shoulder instead of the rim (ala .30-30 Win) or the case mouth (9x19mm Luger). In most "modern" cartridges fired cases typically have enough pressure to expand the brass to fit the chamber to the point it it has zero room left to expand. When you resize rimless cases, you are just trying to reduce the brass casing's outer dimensions enough that it will again fit the chamber with enough slop to let the bolt close. Too little clearance, and the bolt might not close, too much and you might get unrelaible ignition (primer too far from the firing pin) or worse, a case head separation that will leak high pressure gas back at the shooter.

Depending on who made your .32 Rem dies, they might resize the brass more than is required for your reloaded ammo to function well in your M8. In your case, you can probably size it less than your dies can accomplish. A headsapce comparitor and some dial calipers would tell you the difference between your fired cases and your reloaded cases.

*edit*

Here's a simple way to figure out how much to resize bottle-necked cases:

Image

One case is fired, the other's new. In this example, I used a spare .40S&W case. Zero the calipers on the fired case as shown. Then swap to another case and see the difference. In this case the new brass is .004" shorter than my fired brass. When I set up my FL die, I'll shoot for about .002" difference.
Last edited by Fred on Wed Jun 24, 2020 4:47 pm, edited 1 time in total.

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Phyrbird
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Joined: Mon Jan 07, 2013 10:53 pm

Re: Primers backing out

Post by Phyrbird »

FYI from the old SAAMI data...
32 RemSAAMI compr.jpg
32 RemSAAMI compr.jpg (238.1 KiB) Viewed 986 times
Note the crossed circle for the headspace length & diameter of the datum on the shoulder. 8-)
Phyrbird
SOKY

Fred
Posts: 134
Joined: Wed Feb 26, 2014 11:10 pm

Re: Primers backing out

Post by Fred »

Whoops! I guess it's in the SAAMI book so any dies/reamers should be made to that spec. I'll edit my post above. I learned something today. :D

jim18611865
Posts: 100
Joined: Thu May 15, 2014 9:16 pm

Re: Primers backing out

Post by jim18611865 »

Very helpful, thanks a bunch!

Jim

jim18611865
Posts: 100
Joined: Thu May 15, 2014 9:16 pm

Re: Primers backing out

Post by jim18611865 »

Just an update.
I loaded a bunch made by GRUMPA.
I shot 18 of them last weekend, along with a bunch of my reloads.
The GRUMPA loads, which I did not run through my sizing die, had zero primers back out.
I will try and match the shoulder to those cases made by GRUMPA.

Jim

Fred
Posts: 134
Joined: Wed Feb 26, 2014 11:10 pm

Re: Primers backing out

Post by Fred »

As he's no longer with us, I missed my opportunity to purchase GRUMPA's .35 Remington brass. He was as asset to the unpopular/obsolete cartridge shooting community.

In a couple months you'll be in snow and have a heavy winter coat to help soak up some of that recoil. :D

Catskill Tom
Posts: 4
Joined: Thu Jan 21, 2016 12:02 pm

Re: Primers backing out

Post by Catskill Tom »

Mine in .32 Rem. firing factory ammo does back the primer out a bit. I can understand this in a reload, perhaps, if something is not done quite right, but why in a factory round. Yes, the ammo is 50+ years old. Any other thoughts on this? thanks.

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