Thread: Trying something, Eric Cortina method of load development

@dannyb. Thanks for kicking this off mate. It's a really informative read. As a consequence my whole reloading practise has changed. I was a trial and error, hit and miss guy, because I didn't know any better. Been doing that for roughly 40 years.

Quick background; My main rifle is a M77 Mk1 long action with a Shilen barrel chambered 7 x 57. The magazine well is long enough to allow projectiles at jam length to feed.

I developed a load averaging well under minute of angle using my former method. 150 Nosler BT, 45 grn 760 @ 2550 fps. Good, but could be better. Of note, the lowest ES I could obtain with that combo, varying the load, was 21.

The current component shortage led me to googling and ringing around provincial sports stores. I picked up Accubonds, Corelocts, 140 grn Nos BT's and N204 at old school RRP's. I already had sufficient 2209 and 760.

The next step, obtain a Forster Micrometer Bullet seating die. That done, into action. It took a while, as spare time for me is a rare commodity.

I'll try not to bore with a lengthy diatribe and let the photo's speak. Except to say the ES was obtained by increasing loads by .3 of a grain. The seating depths were in 5 thou increments due to component shortage.

The ES was measured using 3 a shot sequence, with a fourth shot to verify if it looked promising. So all ES shown in picture was obtained with a four shot sequence.

Now for the proof of the pudding. Last Monday morning I put the method into practise. Rem Coreloct up first, starting with -5 off jam length.

Not bad, as I'd never been able to got the Corloct under minute of angle before. Of interest to me was that the load was 4 grains over ADI's stated maximum with no pressure signs. 2700 fps, quite respectable. Shots in sequence 1 minute apart, a good five minutes between groups. 3 shot groups due to component shortage. Fascinating to watch the pattern develop.

Next up Accubond, same morning.

I cheated a bit with this one, trying to save components. I hoped to pick up a tight spot quickly. That's pretty much what happened. Again, fascinating to watch it unfold in front of me.
Now I'm really hanging to try the Nos 140BT. Two really good loads so far.
A quick rider: I'll say so my self, without a hint of modesty, I have a reasonable trigger finger.

Thanks again mate.