Thread: Trying something, Eric Cortina method of load development

Well step one is complete. I have shot off 5 shot groups of powder development and got a result I am happy with. 107 Sierra MK in front of AR2209.

Charge weight. Av Velocity. ES.
40.4gr - 2862- 19
40.8gr - 2894- 21
41.2gr - 2933- 22
41.6gr - 2975- 22
42.0gr - 3010- 11
42.4gr - 3022- 28
42.8gr - 3070- 27

I will now use 42.0gr of AR2209 with 0.003 reducing steps of loaded length and try and find the node for accuracy. Erik reckons you will find it within 0.050 of where you start. I will update you alter in the week.

Shot my seating depth ladder today in much calmer conditions, this was reflected in my shooting.
All rounds were loaded at 62gn starting at my charge weight ladder length of 2.843" and working back further away from my jam in 3 thou increments.
I shot all these rounds 1 minute apart and 5 minutes between each 3 shot group.
Anyway I'll load some pics and you can all see how it went.

First group at charge weight ladder length of 2.843" ogive


2.840" opens up slightly


2.837" the first shot is the higher left, the second I muffed and its low center I called it bad I had a cramp as I squeezed it off, the 3rd shot was just below the second about where I expected (I'm picking this group should have been better than the previous)
This picture should be 90degrees left with the single low shot the bottom of the group but I can't rotate it on my phone.


2.834" the best group of the lot and afte loading a few more up to verify speed this is likely were I'll settle


2.831" starting to open up again but not much, one could argue horizontal spread could be shooter error but it felt pretty good


Pic of whole sheet just to show no fliers hidden under the calipers


So where I'm at now is I will load up 9 more rounds
3 at 2.836
3 at 2.834
3 at 2.832
I will shoot these over the chrono so i can collect speed data for ballistic calcs and verify stability.
Looking bloody good though.

Danny, that’s good shooting. I get more excited about groups that show horizontal spread verse vertical like your first pic. Horizontal tends to be shooter. Vertical can be load influenced. Are you using bags or a lead sled type set up?

Originally Posted by Dicko

Danny, that’s good shooting. I get more excited about groups that show horizontal spread verse vertical like your first pic. Horizontal tends to be shooter. Vertical can be load influenced. Are you using bags or a lead sled type set up?

Free standing.......just kidding bipod and a jersey rolled up under the buttstock same as how I shoot in hunting situations

Nice, good to see another bloke who can shoot a decent group off hand.
Just back tracking a bit, why 2217 in stead of the two new wonder powders RL26 or Super P?

Originally Posted by Dicko

Nice, good to see another bloke who can shoot a decent group off hand.
Just back tracking a bit, why 2217 in stead of the two new wonder powders RL26 or Super P?

A few reasons, superformance whilst giving great results has a reputation for being temp sensitive and as I hunt all year round I wanted a temp stable powder also I have no info on if it would also work in 7mm REM MAG.
I had at first actually bought a pottle of superformance with the intent to use it but things changed.
RL26 is about as easy to buy as plutonium however if it were easier to get then I would have considered it for the same reason I went with 2217.
I went with 2217 because if I can get a accurate load worked up for both my 270 and my 7mm REM MAG than it is less different powders I have to have on hand.
Currently I load for 7mm WSM (2217), 270 WIN (2213SC for a mate), my 270 WIN (2217), 308 WIN (IMR 4895 for another mate) and currently for my 7mm REM MAG (2225) so my powder shelf is a little like gunworks.
So I know there are several options for powder that may give better velocity for weight of charge but this was about finding a powder that would work for 2 different calibers and one was always going to be a bit of a compromise.
Next project when this load is finalised is to work up a 168gn Berger load for my 7mm REM MAG using the 2217.
My reasoning may not be sound but it makes sense to me.

2217 is very good powder but i hope you have plenty cause it seems its now as rare as tocking horse poo too ��

Originally Posted by mikee

2217 is very good powder but i hope you have plenty cause it seems its now as rare as tocking horse poo too ��

Just like every other powder for that matter, 2225 is even harder to get than 2217, I am working on getting supplies of 2217

Originally Posted by dannyb

Just a quick update, this is all on hold whilst I sort out a few things, I have sold my Lyman powder dispenser and will be replacing it with a RCBS chargemaster lite.
I have had a change of heart on projectile and powder choice also.
So will take me a few weeks to save some tokens and buy all the bits I need.
Basically I will start the process again and outline progress here.
I'm going to work up 150gn berger VLDH with ADI 2217 in my 270win
And Berger 168gn VLDH and ADI 2217 in my rem mag
All this in the hope of being able to use the one powder for both.
And just cause I'm a bit of a BC slut, I just like that the Berger pills are a lot more consistent
Will be selling off some 2225 and superformance in the hope of recouping some cost towards new stuff.
Will report back here when I'm ready to start again.

Out of interest didn't think to try the Berger 140 Classic hunters in the 270? Higher BC than the 150 VLDs and should be less temperamental to larger jump by mag length restrictions?

Originally Posted by Stocky

Out of interest didn't think to try the Berger 140 Classic hunters in the 270? Higher BC than the 150 VLDs and should be less temperamental to larger jump by mag length restrictions?

I'm using 140gn VLDH not using 150s I had another last minute change of heart and decided not to use 150s I'm fickle and prone to last minute decision changes

I have completed the seating depth testing. Shooting 3 shot groups reducing the seating depth 0.003 each time over 20 strings. I am not completely sure how to interpret the results. Yes there is definitely better and worse groups but not the definitive result I was hoping for. More groups under 0.5" would have been better. And I should have taken more time especially when the sun came out and the target was jumping sideways with the mirage. The 0.14" group was nice but the groups either side were just ho hum.

I would like to do more testing but at this stage will load somewhere to the right of the mirage groups as there is some consistency there. If I can find some time before the first match in Hokonui in Feb to do more work I'll let you know the results. The reality is the rifle will shoot better than me anyway.

The berger site talks of decreasing oal in 40thou steps sometimes ending up 150thou off jam.
Take a lot of shooting to get there at 2&3 thou increments
Some of my rifles like loads 120 or 150 off

Below is an extract from Berger. It is aimed at VLD though. Note the first statement.
For hunting rounds the article does cover mag length elsewhere in the article.
Pure Brian Litz. Although I have also seen him recommend, for target, 10 thou jam, then come back 20 thou (10 thou jump), then back another 20 thou and so on.


"Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don’t give up first. Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:

.010 into (touching) the lands (jam) 6 rounds
.040 off the lands (jump) 6 rounds
.080 off the lands (jump) 6 rounds
.120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:

.010 off the lands (jump) 6 rounds
.050 off the lands (jump) 6 rounds
.090 off the lands (jump) 6 rounds
.130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL towards or away from the lands .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards)."

Zimmer thanks for your input. I am starting at a mag feed length nothing to do with the lands Erik Cortina claims there will be multiple nodes and to move in 0.003 steps as a 0.010 can jump over a node. He reckons you will find a node in 0.050 in the worst case often in much less. It is hard to argue with a guy that has his pedigree. I am not shooting a VLD nor off the lands. Although the results are somewhat mixed I am reasonably happy. Given I know the ES is around 11 for a 5 shot string this load work shows I will have a good result at the longer ranges out past 1000m with minimal vertical stringing. The rest will be up to me.

Originally Posted by zimmer

Below is an extract from Berger. It is aimed at VLD though. Note the first statement.
For hunting rounds the article does cover mag length elsewhere in the article.
Pure Brian Litz. Although I have also seen him recommend, for target, 10 thou jam, then come back 20 thou (10 thou jump), then back another 20 thou and so on.


"Trying to find the COAL that puts you in the sweet spot by moving .002 to .010 will take so long the barrel may be worn out by the time you sort it out if you don’t give up first. Since the sweet spot is .030 to .040 wide we recommend that you conduct the following test to find your rifles VLD sweet spot.

Load 24 rounds at the following COAL if you are a target competition shooter who does not worry about jamming a bullet:

.010 into (touching) the lands (jam) 6 rounds
.040 off the lands (jump) 6 rounds
.080 off the lands (jump) 6 rounds
.120 off the lands (jump) 6 rounds

Load 24 rounds at the following COAL if you are a hunter (pulling a bullet out of the case with your rifling while in the field can be a hunt ending event which must be avoided) or a competition shooter who worries about pulling a bullet during a match:

.010 off the lands (jump) 6 rounds
.050 off the lands (jump) 6 rounds
.090 off the lands (jump) 6 rounds
.130 off the lands (jump) 6 rounds

Shoot 2 (separate) 3 shot groups in fair conditions to see how they group. The remarkable reality of this test is that one of these 4 COALs will outperform the other three by a considerable margin. Once you know which one of these 4 COAL shoots best then you can tweak the COAL towards or away from the lands .002 or .005. Taking the time to set this test up will pay off when you find that your rifle is capable of shooting the VLD bullets very well (even at 100 yards)."

Will give that a crack with the 168s in the rem mag once I've done the velocity ladder, my 270 obviously isn't too fussy with them as they all shot pretty respectable groups.