Thread: Trying something, Eric Cortina method of load development

Interesting afternoon at the range shot my seating depth ladder and have nailed a pretty sweet load.
So yesterday the load that had the best ES and SD shot a less than stellar 1.8" 3 shot group, the ES was 9fps and the SD 4fps which I thought was pretty damn good and warranted further investigation even if the 1.8" 3 shot group at 100y from the charge ladder did leave me feeling a little concerned.
I put the group out of my head and set about loading a seating depth ladder 10 steps, 3 rounds loaded at each step, 3 thou difference seating depth between steps so 30thou difference from closest to jam to furthest from jam.
I went back to the range and set about getting things set up, today I decided not to run the magnetospeed on the barrel as I wanted to make 100% sure there were no external influences that could affect the harmonics, especially as the barrel is an extremely light weight profile and fluted as well.
Immediately right from the first load (which was 3 thou shorter than the charge weight ladder groups) the groups were better, they sort of fluctuated a little then at 12 thou into my seating depth ladder they tightened right up to .8" then 15 thou .5" 18 thou saw the group back out to .7" as did the next 3 groups after that slowly increasing in size again but all sub moa.
Then at 27 thou it shot a .2" clover leaf group, the last group after that was only 2 rounds as I ran out of prepped brass but it opened back out up to 1.1".
So in conclusion I will settle on the 15 thou group that was .5" and some might ask why not the .2" seating depth and my reason is the .5" group was right in the middle of a big stable node of sub moa group producing seating depths from 12thou-27thou the last group in that node was the .2" group before it opened right out to 1.1" just 3 thou deeper so my logic is that the .2" group is right on the very edge of that accuracy node where as the .5" group is closer to my jam and has good grouping over 15 thou of tolerance so is right in the middle of that accuracy node.
Whilst this may come accross as tedious and OCD it definitely works, the other issue is that the factory trigger on this rifle is a heavy bitch and will need sorting I suspect it will be easier to shoot good groups once I've had the trigger lightened.
All in all happy to have a nice accurate load sorted. I will load up 6 or 9 confirmation loads to krono for velocity validation as I didn't krono the seating depth ladder.
End result should see 178gn eldm's at a velocity in excess of 2950fps.
I'll post pics of the charge ladder and seating ladder later this evening