Thread: Trying something, Eric Cortina method of load development

Nice!!!!! Looks like you have a very good load sorted

Originally Posted by MMC3

Thanks distant stalker for that extra analysis. I will let you know how I get on with the next test batch in a few days.
@R93 - the cold bore first shot velocity difference and clean bore vs fouled bore velocity difference is a common phenomenon. The long-range target stuff that I do is out to 900yds - you get two 'sighters', then (normally) 10 counting shots. The first shot of the day is pretty much always lower vertically, usually more so for a clean bore, due to that velocity difference.

My F class rifles clean cold bore shots are 1 MOA low for my first sighter I add ! MOA elevation and take it off for the second if your wind call is correct you get 2 keepers very handy in the F disciplines.

Right finally have my new press installed and loaded up final load test and confirmation.
I loaded up 6 rounds a month ago on my old press and it was bloody diabolic trying to seat accurately.
I took those 6 rounds to the range and shot them.
The first 3 were seated at 2.834" ogive length and whilst the speed was consistent it was a bloody awful group
Which surprised me as I had already found this seating depth and charge weight to shoot very very well.
I also shot 3 at 2.831" ogive and this shot a half inch group which is what I expected from the first load.
My mate pointed out to me that when i shot the first group i was lying prone but nearly 70° to the rifle which would likely have thrown my parallax out and possibly the cause of the poor group.
So rather than suffer using my old press again I bought a new press off a forum member and waited for that to arrive before loading anymore rounds.
Fast forward 1 month.
Loaded up 3 more at 2.834" on the new press and what a delight it was to use a press that seated accurately every time.
Went to the range and put 3 factory rounds through just to check the rifle was all good and foul the barrel.
Then shot my 3 hand loaded Berger rounds.
I think I'm done.
But I'll let the pic do the talking.





Today's fps are circled down the bottom of the list and are consistent with the last lot that I made up at the same spec as per 2 lines above.

Fucked if I know why the last pic is upside down sorry guys

For the doubters here's the pic of the target with nothing in the way.

Hopefully fixed the upside down pic

now write that recipe with ALL its details on the wall above press with vivid.......tis a keeper mate.....

Originally Posted by Micky Duck

now write that recipe with ALL its details on the wall above press with vivid.......tis a keeper mate.....

Tis in my load diary

Ballistics for anyone interested.

So correct me if im wrong.
Start with powder load ladder. Take the load with best ES and SD, not necessarily the best ‘grouping’ on target.
Then proceed to seating depth ladder: work out ‘jam’ length… then ladder jam length-0.015-0.020”, then 3rounds at 0.003” intervals…. What are we looking at measuring with this? Just ES and SD, or target group size?
Ive done a powder ladder, but unfortunately the best group size and best ES didn’t marry up…. So do i go with the best ES and see if the group size comes in with the different seating depth ladder? Or just go with the powder charge with the best grouping, and see if i can improve group size and ES with the seating depth ladder?
My powder ladder was all done with the same Coal: 0.025” off jam length

Originally Posted by micknz

So correct me if im wrong.
Start with powder load ladder. Take the load with best ES and SD, not necessarily the best ‘grouping’ on target.
Then proceed to seating depth ladder: work out ‘jam’ length… then ladder jam length-0.015-0.020”, then 3rounds at 0.003” intervals…. What are we looking at measuring with this? Just ES and SD, or target group size?
Ive done a powder ladder, but unfortunately the best group size and best ES didn’t marry up…. So do i go with the best ES and see if the group size comes in with the different seating depth ladder? Or just go with the powder charge with the best grouping, and see if i can improve group size and ES with the seating depth ladder?
My powder ladder was all done with the same Coal: 0.025” off jam length

Best es, then fiddle seating depth to tune group size

👍Thanks…. I’ll be lucky to have any projectiles left after all the load development (6.5mm eld m) 🤔

Originally Posted by micknz

👍Thanks…. I’ll be lucky to have any projectiles left after all the load development (6.5mm eld m) 🤔

Sad sign of the times unfortunately, currently developing a load for my 308 and I'm being extremely frugal just loaded to saami length and charge weight ladder, got 2 reasonable loads out of it, currently loading 3 more of each to confirm data and will pick the best and leave it at that.
As luck would have it 1 is .5" 3 shot group at 100 yards the other is .7" the chrono was playing up so only got speed of 2 rounds at each of those charge weights but looks promising at around 12-15 fps spread for both loads.
Normally I would go hard and do seating depth ladders to really tune the load but I really don't have the luxury of components and am unlikely to anytime soon like the rest of us.

I found this to be quite helpful
Load Development Model XLS


Makes it easier for a simple person like me to interpret results visually
From here Load Development Analysis

I like Erics videos except the one where he criticizes neck sizing. The comments defending neck sizing were awesome and really wound up Eric.