RMajors
Lil-Rokslider
I thought I'd share my experience from my 270 wsm load development for my T3x lite with Grand powder as data has been somewhat tough for me to find. I also tried Magpro, but it shot awful in my gun, and velocity was lackluster as well. I started with Norma brass, Grand powder, Federal 215m primers, and a member here sold me a couple boxes of 129gr lrx. My start charge was 73gr, mid charge 74gr, and max charge of 75gr. The first 2 charges shot ok, under an inch with triangular groupings, but the max charge shot exceptionally well. First 2 went in the same hole, and the third was about 3/8" directly above. I called high on it when I broke the shot off as well. The velocity was 3350fps at the max charge, and I believe the start was around 3250. The powder behaved as you would expect, giving 50fps for each grain increase. COAL was 2.85 per Barnes' data, but the max charge rounds were a hair longer as the charge was lightly compressed. I used a 3" drop tube with my new Area 419 funnel (which are sweet btw) to stuff the powder in, and didn't have signs of pressure, outside of flat primers. Hodgdon's data showed the pressure to be 58.8k psi at their max charge of 75gr, but my brass had a bit less capacity I believe, as my velocity was higher. But I felt safe to fill it up to the neck with their max pressure being under 60k psi. SD was pretty good, but I didn't write it down. I'll look at my chronograph next time I'm near it and get an actual number, but I feel safe saying it was under 15fps. Feel free to reach out if you have questions or would like to see pictures of the target or anything. I'll try to remember to add pictures and sd.
