Primers jumping the pocket?

[Cj7deerslayer]

Ok guys i have a weird problem. I needed to test the mainspring in a 686 so I sized and primed some hornady .357 magnum brass with winchester small pistol primers. I also tried with speer brass. I did this because Its been raining for three days and I cAnt get out to shoot loaded cartridges. On every shot I tried firing with the primed cases the primer jumped out of the pocket far enough that I couldn't advance the cylinder to the next round.
The primers were well seated before firing. Any ideas here would be appreciated.

 

[Twicepop]

When you shoot an unloaded cartridge the primer backs out slightly because there isn't sufficient pressure/force to force the brass back against the recoil shield. With a loaded round, Newton's third law comes into play, for every action there is an equal and opposite reaction. The force of the bullet traveling forward pushes back against the case pushing it against the recoil shield re-seating the primer flush with the case head.

 

[MikeT124]

If you drill the flash hole bigger the pressure of the primer blast will be relieved and you will be able to continue your testing. But do not reload the brass you have drilled out because it will allow excessive pressure into the main part of the case and the results could very well be damaging to the firearm or yourself. Additionally if the hole is large enough expect the primer anvil to go flying out the barrel headed to parts unknown. Upon completion of your testing flaten and discard the brass used for the tests.

Mike

 

[edwardware]

On every shot I tried firing with the primed cases the primer jumped out of the pocket far enough that I couldn't advance the cylinder to the next round.

It happens every time (bottleneck too!), you just don't notice with a full charge to reseat the case over the primer.

Drilling the flash holes will reduce the effect.

 

[3Ackleys]

Probably easier to put on a rain coat and shoot than drilling flash holes.

 

[Uncle Ed]

Below from the Sierra reloading manual.

 

[243winxb]

A rifle primer alone, make about 23,000 psi in the pocket. No powder needed.

https://discover.dtic.mil

 

[pirate ammo]

Try small pistol magnum primers.

 

[Uncle Ed]

Below excessive head clearance/headspace, case stretch and the primer backing out and being reseated.

NOTE, my 30-30 at 38,000 cup or 43,000 psi always has the primers protruding. This is because the chamber pressure is not great enough to push the case back against the bolt face.