257 RPM

huntinfool18

Well-Known Member
Joined
Aug 2, 2006
Messages
2,842
Location
Wyoming
I finally got a scope on my 257 and put a few rounds down range. I did a really quick pressure test a couple weeks ago with staball hd powder and 134eld. Took it up to 71grs and 3370fps. For this trip i didn't do anything special loaded 69gr of staball hd with a 134 at the lands no other load work done.
First 3 shots with a scope on are the black target on once fired brass, average 3255fps
After letting the barrel cool and a couple clicks on the scope I fired 1 shot to confirm zero then dialed up 1moa and set the rifle aside while I shot my 7 mag. Next 3shots in the square. Had to let the rifle cool and take a pic. Couldn't leave well enough alone so I fired 2 more. Of course I had to mess it up. It was all me. I'm sure it would have been in the group as well. Gun went off right when a gust of wind came up. This was virgin brass with the same load as above. 69gr staball hd and a 134 at the lands. Was only 5 fps slower then the once fired brass at 3250fps. Pretty impressed with the rifle so far.
 

Attachments

  • IMG_1544.jpeg
    IMG_1544.jpeg
    203 KB · Views: 43
  • IMG_1546.jpeg
    IMG_1546.jpeg
    252 KB · Views: 47
  • IMG_1547.jpeg
    IMG_1547.jpeg
    258.4 KB · Views: 46
Last edited:
I finally got a scope on my 257 and put a few rounds down range. I did a really quick pressure test a couple weeks ago with staball hd powder and 134eld. Took it up to 71grs and 3370fps. For this trip i didn't do anything special loaded 69gr of staball hd with a 134 at the lands no other load work done.
First 3 shots with a scope on are the black target on once fired brass, average 3255fps
After letting the barrel cool and a couple clicks on the scope I fired 1 shot to confirm zero then dialed up 1moa and set the rifle aside while I shot my 7 mag. Next 3shots in the square. Had to let the rifle cool and take a pic. Couldn't leave well enough alone so I fired 2 more. Of course I had to mess it up. It was all me. I'm sure it would have been in the group as well. Gun went off right when a gust of wind came up. This was virgin brass with the same load as above. 69gr staball hd and a 134 at the lands. Was only 5 fps slower then the once fired brass at 3250fps. Pretty impressed with the rifle so far.
Cool! Rifle specs?
 
I finally got a scope on my 257 and put a few rounds down range. I did a really quick pressure test a couple weeks ago with staball hd powder and 134eld. Took it up to 71grs and 3370fps. For this trip i didn't do anything special loaded 69gr of staball hd with a 134 at the lands no other load work done.
First 3 shots with a scope on are the black target on once fired brass, average 3255fps
After letting the barrel cool and a couple clicks on the scope I fired 1 shot to confirm zero then dialed up 1moa and set the rifle aside while I shot my 7 mag. Next 3shots in the square. Had to let the rifle cool and take a pic. Couldn't leave well enough alone so I fired 2 more. Of course I had to mess it up. It was all me. I'm sure it would have been in the group as well. Gun went off right when a gust of wind came up. This was virgin brass with the same load as above. 69gr staball hd and a 134 at the lands. Was only 5 fps slower then the once fired brass at 3250fps. Pretty impressed with the rifle so far.
Gotta love them quarter bores.
 
For you numbers nerds, that's 1800fps and 1000ft lbs energy at 1400yds.
And to think I was going to sell this barrel a few weeks ago 😲
At my altitude (3300'), with your info, 3250 FPS G7=.325, I was calculating:
1400Y = 1631 FPS/792 FT-LBS. I must be doing something wrong. It is still no slouch, though.

I considered building a .25 cal wildcat out of the RPM in 2021, but I could not secure enough brass then, so I abandoned it and went with the .257 WBY instead.

My .257 WBY propels the 145 Black Hole (G7=.371) at 3090 FPS out of a 22" barrel during my powder pressure test with more room to spare. 1400Y = 1684 FPS/913 FT-LBS.
 
Top