Re: .257, 6.5mm and 270 Allen Mags, New Family or Rounds...
Rl-25 is a good powder and a pretty good match for the 257 Wby with most bullet weights especially the 115 and 120 gr class bullets.
There are slower powders out there though, much slower. This is a good thing as RL-25 is a great powder in the 257 STW with 100 gr bullets but it is really to fast in burn rate for anything much higher to get peak velocities.
In teh 257 STW, Retumbo is a much better powder for bullets in the 115 to 145 gr weight as it will provide better consistancy and higher velocity the Rl-25 because it is a slower burning powder.
In my 257 AM, Rl-25 is very fast for even the 100 gr pills which I do not recommend in this round. I will develope loads for the 100 gr Bonded Core FBHP but velocity spread will be relatively high as it generally is in the STW, just worse in the larger AM.
I recommend startign with the 115 gr bullets as light weight options in the 257 AM and preferably the 130 gr Bonded Core FBHP from Wildcat Bullets.
With this bullet weight Retumbo will be the best powder I suspect along with the 145 gr pill.
There will also be a 150 gr FBHP but testing needs to be done to see if this bullet will stabilize in the 1-10" twist barrel or if it will need a 1-9" twist to keep the bullets on point.
Other powders that will be tested with the 145 adn 150 gr bullets will be H-50BMG(possible powder bridging problems may occur with this powder at the case neck, we will have to see) and AA 8700 which is nearly the same as H-870 which would have been a hell of a powder for this round if it were not dropped from the Hodgdon line.
Only one person I know of is making these weights in the 257 caliber and he is Richard Graves, owner of Wildcat Bullets in Alberta Canada. His bullets have performed to perfection in high velocity testing with the 257 STW and I suspect will perform the same in the larger 257 AM as well.
Kirby Allen (50)
Allen Precision Shooting
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