Jump to content


Photo

Stgw.57/PE-57 7.5x55 Swiss Handloading


  • Please log in to reply
1 reply to this topic

#1 Syntax Error

Syntax Error

    New Member

  • Regular Group
  • 1 posts

Posted 14 December 2015 - 04:42 PM

I was wondering if anyone can share their experiences for handloading for the Sturmgewehr 57 rifle with its unique double shoulder chamber. From what I have gathered, the second set shoulder in the chamber is to allow the bolt and the chambered cartridge to pinch the shoulder slightly to prevent the bolt from bouncing back under full auto fire, for example. I was wondering if anyone has had any experiences for resizing for brass that has been once fired out of this particular chamber.

 

I have read up on some experiences from the Swiss Rifle Forum about a user whose Stgw.57 blew up on him and he seems to claim that it is because of this double shoulder and the chamber fluting allowing for the brass to be stressed at a particular existing flute under fire and rupture a case, but I am somewhat skeptical of this analysis. It would seem to me that this particular owner's rifle may have either been improperly sized and allowed for an out-of-battery detonation, or his load was not a safe level, or his brass was somehow compromised previously somehow.

 

It seems to me with a reasonable load and strong brass, with proper resizing to take account of the double shoulder, that reloading for a Stgw.57 should be possible and retain a reasonable margin of safety. I have experience for reloading for other fluted chamber firearms such as an HK-91 series of rifle, and have had no issues. I plan on using Prvi Partizan brass and annealing the cases after every firing as well.


Edited by Syntax Error, 14 December 2015 - 04:43 PM.

  • 0

#2 amafrank

amafrank

    Long Time RKI Member

  • Regular Group
  • 165 posts
  • Gender:Male
  • Location:Indianapolis, USA
  • Interests:MG's of all types. Cannons that can be transported by normal people. Fine firearms of all descriptions.

Posted 21 February 2016 - 09:47 PM

I have loaded for my 57 and AMT. The AMT doesn't have the double shoulder but is fluted as well. I have been taking the cases fired in the 57 and reloading them to fire in the K31. That straightens out the shoulder and flutes so I can load again for the 57. I can't see any issues as long as you use a powder similar to the original GP11. I think that there can be problems if you use a powder either way too fast or slow for the locking system. Anything that changes the timing of the pressure curve can change the way the system cycles. According to all I've read the whole point of the flap / roller system instead of the plain rollers of the Cetme/HK is to allow for a wider range of loading for the ammunition. The HK seems to be a bit more sensitive to loading.

As for loading the ammo for the 57 you just need to insure that the shoulder of the case is where its supposed to be. The double shoulder is only where the outside of the shoulder is pushed back a little. The main part of it is a datum that sets the headspace of the cartridge in the rifle whether its the K31 or the Stgw 57. You'll find that loading a round into the 57 will squish the shoulder whether it fires or not. It still indexes off the datum of the shoulder even if it gets squished. You can take a squished one out of the 57 and drop it into a K31 or any of the other straight pulls and it will still headspace fine. You will have to insure that the bullet is seated to the proper depth since the shape of the bullet is likely to be different from the GP11 type. I've been loading 175gr Sierra Match Kings for all the Swiss rifles. Best accuracy is gained by using a depth that puts the bullet 10 to 20 thousandths off the lands and that will likely be different for each rifle so figure the depth for each rifle....
Reloader 17 is said to be the type of powder used in the original GP11 and it works well for my purposes.
Hope something there helps

Frank


  • 0