I wanted to put together some data on load development from my 257 wby mag after doing a lot of research and reading, and looking through manuals. I started with two powders in load development and quickly narrowed it down to RL-25 after the 7828 was scattering and hit pressure before I hit book max from two load manuals.
This is why load data below should be used with caution as different rifles and powder lots can react very different and may not be safe. Always start low and work up to safe maximums. The data below is for demonstrating load development and velocity in my rifle, be safe with yours.
Rifle: remington cdl sf 26" tube
cci 250 mag primer
Swift Sciricco 2 100 grain pill
I began barrel break in after bore sighting with a ladder test at 250 yards, not far enough but I was mainly trying to determine max powder charge and maybe find nodes. I first worked up to 75.5 with no pressure whatsoever in 90 degree temps the last week of August. I proceeded to work up to 77.3 and still have no pressure shooting this load in 85-90 degree days.
I was not happy with the ladder from 250 so I started over at 500 yards to spread things out a little. Ended up with 3 nodes and it so happened one of them was from 76.7 to 77.3 in .3 gr increments. I split it at 77.0 as it had .5" vertical between two shots at 500 So I ran with it, if I wanted moderate velocities I would have got a 25-06!
My next challenge was to get horizontal spread out, the wind was blowing on 500 yard test so I moved onto a seating depth test. My original load was 2.69" base to ogive, I loaded up 3 shot groups in .010" and .020" longer and shorter to see if group size changed. This was also the first time I ran it over a chronograph.
I must have been lucky when I set up my seating die because after seating depth test .02" shorter than the 2.69" was what worked best. Anything longer opened up quickly, the shorter loads grouped much better, no reason to chase rifling here.
The load data run through ballistic ae looks like a flat shooter to me, now it's time for antelope season. .75" 3 shot group at 100 yards with average velocity at 3700 I am pleased with this rifle. Didn't do 5 shot groups because I am sure the life span of this barrel isn't going to be all that great but it should be a hammer!
Again these are over max loads, be safe and work from low starting charges.