Thread: Trying something, Eric Cortina method of load development

After watching the Erik Cortina YouTube videos and following this thread, I thought I’d give it a go. Thanks DannyB for starting it up. I waste far too much time and too many components on load testing, so any ‘short cut’ that works is great. The test rifle is a Savage actioned ‘back-up’ 308 Winchester target rifle for F-TR and F-PR competition and practice.

Specs are:
Savage Model 16 stainless action with a Rifle Basix trigger, epoxy bedded in a Boyds laminate target-style stock. Barrel is 28” 1:10 twist stainless M24 profile (straight taper to 0.950” muzzle), made by Hugh Bradley. Chambered with a 308 Winchester tight-neck ‘Palma’ reamer by Les Grimsey. It has been showing some good accuracy potential. Scope is a Sightron SIII 8-32x56 in Leupold rings and I’ll be using an F-TR style bipod and rear bag.

I have some Sierra 155grn ‘Palma’ projectiles that haven’t been shot in this rifle before, to use for this test.

For the velocity test stage, my load specs are:
Lapua Small Rifle Primer 308Win brass (annealed with an AMP annealer), CCI 450 primers, Sierra 155 Palma projectiles, seated 20 thou off the lands (measured with a firm push into the lands with a Hornady seating depth gauge).

Load is 8208 powder, with four each of: 45.3, 45.5, 45.7, 45.9 and 46.1 grains (three for data, one extra in case the chronograph doesn’t register a shot). These loads are up to a grain over the maximum of the Sierra manual. It works for me, as the small rifle primer brass typically needs more powder to reach the same velocity/pressure as large rifle primer brass, and I’ve been shooting similar loads in this rifle with no pressure issues. It may not work for you, so it goes without saying to stay with reloading manual loads.

I’m a fan of small steps, as I think nodes can be quite small (and easy to miss with bigger steps).

Chronograph results (with a LabRadar chronograph):
45.3 – 3002, 3009, 2991 – ES = 18 – SD = 9.1
45.5 – 3005, 3006, 3006, 3011 – ES = 7 – SD = 3.0
45.7 – 3031, 3027, 3014 – ES = 17 – SD = 8.7
45.9 – 3050, 3033, 3042 – ES = 17 – SD = 8.4
46.1 – 3064, 3041, 3058 – ES =23 – SD = 9.7

45.5 looks like the clear winner. Given the ES of 2 after three shots, the fourth was fired and it is still very good. The bolt had very slight resistance to lifting for the 46.1 load, so I’m happy to be 0.6grn under that.

Forecast to rain tomorrow, so I’ll load up the length-test series, and hopefully test on Friday and report.

Any comments, questions or critique most welcome.