Thread: Trying something, Eric Cortina method of load development

Some very thorough testing there @dannyb that fits pretty well with the berger seating depth recommendations, I'm pretty sure theirs goes 10 thou jam, 20 thou jump, 50 thou jump, and so on in 30 thou increments. Was your node right around 15 or 20 thou jump?

Originally Posted by Rated M for Magnum

Some very thorough testing there @dannyb that fits pretty well with the berger seating depth recommendations, I'm pretty sure theirs goes 10 thou jam, 20 thou jump, 50 thou jump, and so on in 30 thou increments. Was your node right around 15 or 20 thou jump?

depending on which load shoots the best of the 2 seating depths it will either be about 15 thou or 21 thou or there abouts, currently at work so can't check what I wrote down as my jam measurement

Update....so i took the 2 loads i thought would be the goods to the range loaded 10x for each load which gave me 5 for a group validation and 5 for krono data.
It didn't go well both loads had opened up shooting 1.8" and 1.5" groups and then even worse with the magnetospeed hanging off the muzzle.





Not ideal and a little frustrating
The es and sd were still really stable so I revisited the seating depth that shot the very best group 2.638" loaded up 6 rounds 3 for group validation and 3 for krono data

Both shot extremely well again, even with the krono fitted, both 3 shot groups were under .4" I did note a slight poi shoft with the krono fitted but still a great 3 shot group.
So this load has now shot 3 sub .4" groups including the seating depth ladder. I'm gonna call that confirmed good.
The velocity was a little lower but no slouch at 2928fps avg with an sd of 9fps and an es of 18fps

Magnetospeed attached slight poi shift right


No magnetospeed


Original seating depth ladder group.



......time to load some ammo

good to see performance with the 0.638 depth confirmed

Depending on what sort of accuracy goal you are after? I'd recommend shooting at least 4 shot groups, preferably 5 shots to gather your initial data, 3 shot groups can be fools gold, has been for me anyway sometimes.

I'll load 5 of each load, if after 3 clearly shit, stop on that load. If grouping in nice pattern or touching keep shooting string so you end up with 5 of potential good load verified.

You can then just pull the ones easily you don't use when get home with a cam-lock puller, recharge with load and seating depth. I have a wee RCBS partner press($190) take to range now for seating depth, can just load up a box at longest seating depth want or jam, then adjust at range to whatever plan is? Once start looking good just push more down to that depth, saves a lot of trips or seating heaps you might pull later.

man if I had a dollar for everytime Ive heard that one...3 shots just prove rifle goes bag etc..... what a crock of poohs.
if you really want,if you really really want... to proove a load is CONSISTANT... and insist on a 5-10 shot group,shoot it 1-2 shots at a time over a month...same target,different days and conditions...but in reality Danny now has a load HE IS CONFIDENT IN...and that right there my friends is 99% of the battle won.
He KNOWS it will poke hole in animals vitals if he does his bit right....END OF LOAD DEVELOPMENT...
write down load recipe on wall above loading bench with vivid felt pen and stop wasting component and go fill the freezer.

I have literally shot this load 9 x now, same poi , 2 of the 3 shot groups were shot 1 immediately after the other just different targets.
The only poi shift has been when i chucked the magnetospeed on the end of the barrel. You know what ? I've never needed 3 shots to drop a deer but if this rifle can stack the first 3 rounds like that every time I'm happy as, in reality what i shot today the 2 x 3 shot groups 1 after the other at different targets would be akin to a 6 shot 1/2 moa group even with the poi shift from adding the magnetospeed. But hey I'm not here to prove myself to anyone. MD your right I've gone through enough components.....I'm not blowing through anymore just to convince anyone on here. The next shots through this rifle will be at deer.

Just a reminder.....this shows were i started and where I ended up...



I'm not shooting PRS or bench at 1000y guys it's an ultralight hunting rifle, either way I'm more than confident it'll put all 5 rounds in the mag where I tell it, as long as I do my bit right

Awesome

Productive afternoon, 50 make deer deader make gun go bang thingies ready to go

when you have a spare 10 minutes..... get a blank target...place each of your shot up ones ontop of it in turn and mark your bullet holes onto the blank target...so you will end up with one target with 15-20-25 impacts marked on it...a composite group if you will....
be interesting to see just how "bad' it is......would be indicative (hows that for a wheelbarrow word before 9AM?) of a chuck it together loads preformance .

So an interesting issue cropped up the other day with the Dirty Ackley....I changed from a radial brake to a directional brake due to the radial brake not really doing enough to reduce the recoil on what is a very light rifle (3kg ready to hunt) but decently recoiling cartridge....
I went to the range to double check zero and shot a couple if 3 shot groups, made a slight tweak on the zero, then offered my mate a few shots as he's a bit of a gun slut like me
he also shot a couple of really tight groups but commented that the bolt was a bit tight to close when chambering rounds
I had not experienced this myself but immediately suspected maybe I had not bumped the shoulder back enough when I full length sized the cases
Well it finally got the better of me so I checked the remaining 40 odd rounds and yup most of them were hard to chamber (I did not force them, stopped if I felt resistance), checked the fired cases for length just to confirm trimming wasn't the issue, it wasn't....out of 40 odd rounds I have 5 left that chambered ok looks like I'll be pulling the lot and full length sizing them then reassembling them.
To double confirm it was the shoulder bump I used a fired case that was also hard to chamber and wound the sizing die down until the case chambered nicely.....which I should've done form the beginning
Guess I know what I'll be doing on my next days off, I'm happy with the load, but will run a couple 3 shot groups through once I have re made the rounds to confirm that all is hunky dory.
I was a little too concerned about over working the brass and didn't wind the sizing die down far enough after fire forming. Due to the forming loads not being very hot they didn't require as much pressure when full length sizing to chamber nicely otherwise I would of noticed when I was doing my charge ladder (in hindsight I should've checked the brass chambered when I resized the charge ladder cases). The charger ladder loads were certainly full power loads explaining why some of the higher load cases weren't bumped back sufficiently. I hope that makes sense.
lesson learnt, hopefully this will help someone else if they come up against the same thing.

If you can get yourself a redding body die, it's possible to run a loaded round through them just to nudge the shoulder a touch.

They might not make one for something so unusual though.

Originally Posted by Pommy

If you can get yourself a redding body die, it's possible to run a loaded round through them just to nudge the shoulder a touch.

They might not make one for something so unusual though.

thanks for the suggestion, would be great if it was a thing but I doubt it and even if it is a thing finding one in NZ would be little to no chance....I'm resigned to pulling the loads I have done and learning from my lesson.....first time fire forming brass....it's been a process

Originally Posted by dannyb

thanks for the suggestion, would be great if it was a thing but I doubt it and even if it is a thing finding one in NZ would be little to no chance....I'm resigned to pulling the loads I have done and learning from my lesson.....first time fire forming brass....it's been a process

Just go out in a paddock and run them all through the chamber a couple of times, that will cure them if close to chambering. Fire any that are too tight.
The donut ring on the neck and a normal load method gives a much more consistent fire form case than a soft load.