Firing Live Primers in Otherwise Empty Cases


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Bart B.
January 5, 2010, 06:52 PM
Steve Marshall comments on firing an empty primed case in an earlier thread titled: "Firing a primer in an empty case?"
Some shoulders might get moved forward. Facts are, with rimless bottleneck cases, the shoulder gets set back a few thousandths. This happens with live primers as well as deactivated (soaking them in water for a few minutes) ones that just "click" instead of the loud pop of their primer detonating.

And with live rounds, too. When the powder burns and raises pressure towards maximum, the back of the case stretches back a little but the primer pushes out of its pocket a few thousandths. As pressure peaks and the case head gets pushed back against the bolt face, that seats the fired primer flush with the case head.

PS:
I've no idea why this thread was locked. Must be a sensitive issue to some folks for some reason.

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Loosenock
January 6, 2010, 09:23 AM
At one time I had a Winchester M70 in a .22 Hornet that was rechambered for the .22 Kilborne Hornet. It was just the Hornet with a straight walled case. I tried several times with several brands of primers and the effort was futile. Even with a low charge of powder......case forming was not entirely complete. I settled on just firing factory ammo in the improved chamber to get the results I was looking for.

That was just my own personal experience...I think results may vary.

'Loose

Dr. Tad Hussein Winslow
January 6, 2010, 12:09 PM
I thought you needed to fire at least wax or paper or similar to generate enough pressure to fireform an "improved" case with a primer, OR use a wee bit o' powder and no projectile?

skidooman603
January 6, 2010, 12:21 PM
I still have no idea why my thread was locked either The moderator must have something offensive :scrutiny:

Loosenock
January 6, 2010, 04:26 PM
I did Doc. I cut .22 cal biscuits with the neck of the case out of cooling wax.

I even tried like 3-4 grains of 4227 and corn meal. Only about 50% formed. I then gave up and just fired factory ammo or Hornet cases loaded to to factory velocities. Got 100% then.

I've also shot a few 1000 .38 spl wax bullets out of sized .38 brass with just primers. Never ever needed to resize the brass......those were just straight cases though. I was shooting .38 cal wax bullets up til last fall until the price of primers went through the roof.

'Loose

Steve Marshall
January 6, 2010, 09:08 PM
Bart B., Thanks ever so much for reminding me to proof posts. For all my fans, the shoulders will move back, not forward, when "shooting" a primed case.

lost river rat
January 6, 2010, 09:33 PM
The best fire forming is to use full loads in the parent cartridge. This can only be done if the improved round will head space corretly. Example: On the 30 Gibbs, we used to neck them up to .33 and then back down to .308 with the Gibbs die. This would give enough of a shoulder to heads space on.

Cases with a small charge of powder and filled with corn meal will work, but it takes a lot of experimenting to get it work reliably

Firing a primer in a bottleneck case will bump the shoulder back. The primer force pushes the primer into the bolt face and the case forward into the chamber as discussed above. This action bumbs the shoulder. It becomes a problem with repeated firings. The rubber bullet loads and really low velocity cast bullet loads require drilling out the primer flash hole so the primer force on the bolt face is reduced and less shoulder set back. I mark this cases with a hacksaw slot across the back of the case head so I don't load a high pressure load in them and blow the pimer in my face. Works with rubber bullets in a revolver (sometimes the primers back out enough to not allow the cylinder to rotate)

Art Eatman
January 7, 2010, 12:54 AM
I went and looked. Sorry for no closing statement.

When a question is asked, as a thread title, and that question has been answered, generally there's no point in continuing on until the horse is not just dead but smelly.

Thread drift causes closings, also, like getting into discussions of fire forming instead of staying with the subject of the opening post.

:D, Art

skidooman603
January 7, 2010, 05:04 AM
Thank You Art for the explanation. As I mentioned in my thread to moderator, just wanted to make sure I had not broken a rule or something to get it closed.

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