Thread: Trying something, Eric Cortina method of load development

It's a very clear way to approach load development.

One thing I would say when doing your seating depth test is to remember an important piece of context of his videos: he's shooting Bergers. He's also an extremely good F-Class shooter so the nut behind the butt isn't introducing much noise / human error into the equation.

The VLD's are notoriously fussy over seating depth and a few thou one way or the other is important. I think the less aggressive the ogive, the more tangent and less secant the bullet, the more forgiving on seating depth, and the more coarse you need to go in your adjustments to notice a difference.

So I'm watching with interest. My prediction is you aren't going to see a huge difference in your seating depth test, with such fine adjustments on a non-VLD bullet, and it'll be hard to spot a clear winner when factoring in any human error too.

Standing by to eat my words

Surely if you load to a standard COAL (like 2.8" on a .308) and it shoots good, call it a day?

Seen a lot of people claim their hunting rifle (Tikka/Savage/Howa whatever) is a 1/4 minute gun... not seen anyone outside of Olympic .22 being able to hold a rifle that steady (that wasn't locked in a shooting rest/vise), so how can you claim to have a rifle+ammo setup that shoots within that?

not to mention that 3 round groups mean zilch... benchrest is 5 or 10 shot groups.

Originally Posted by caberslash

Surely if you load to a standard COAL (like 2.8" on a .308) and it shoots good, call it a day?

Seen a lot of people claim their hunting rifle (Tikka/Savage/Howa whatever) is a 1/4 minute gun... not seen anyone outside of Olympic .22 being able to hold a rifle that steady (that wasn't locked in a shooting rest/vise), so how can you claim to have a rifle+ammo setup that shoots within that?

not to mention that 3 round groups mean zilch... benchrest is 5 or 10 shot groups.

You raise a valid point, I should be very clear I am no Olympic marksman this is true, but I can shoot and at 100 yards I'm confident in knowing if I have pulled a shot or not.
Your also correct 3 round groups mean zip in bench rest, however I don't shoot F class or PRS or any of that, I am just using Cortina's methods to develop a load for my hunting rifle.
If my hunting rifle shoots consistent speed and tight 3 shot groups that's plenty good enough for me.
I'm sharing my experience because the way it is explained just makes sense to me and if I can use some of his methods for developing my hunting loads and his explanations help me understand whats going on and what relationship the changes I make are showing in my groups then surely this is a good thing.

Your also right there is nothing wrong with a sammi spec load that shoots well in your rifle and if you have that great
I load all my own ammo so this opens up opportunities to improve or gain better accuracy so why not have a crack at it.
Plus I enjoy the challenge, I'm not out to prove anything or make massive claims, all my loads thus far for my rifles are sub moa some considerably even with 5 shot groups but you know what ? The deer don't seem to care much if I hit them an inch high or low or whatever so whilst this might seem a little OCD it's really just me playing and having a bit of fun so I won't loose too much sleep over it all.
Hopefully I'm learning too

Originally Posted by dannyb

You raise a valid point, I should be very clear I am no Olympic marksman this is true, but I can shoot and at 100 yards I'm confident in knowing if I have pulled a shot or not.
Your also correct 3 round groups mean zip in bench rest, however I don't shoot F class or PRS or any of that, I am just using Cortina's methods to develop a load for my hunting rifle.
If my hunting rifle shoots consistent speed and tight 3 shot groups that's plenty good enough for me.
I'm sharing my experience because the way it is explained just makes sense to me and if I can use some of his methods for developing my hunting loads and his explanations help me understand whats going on and what relationship the changes I make are showing in my groups then surely this is a good thing.

Your also right there is nothing wrong with a sammi spec load that shoots well in your rifle and if you have that great
I load all my own ammo so this opens up opportunities to improve or gain better accuracy so why not have a crack at it.
Plus I enjoy the challenge, I'm not out to prove anything or make massive claims, all my loads thus far for my rifles are sub moa some considerably even with 5 shot groups but you know what ? The deer don't seem to care much if I hit them an inch high or low or whatever so whilst this might seem a little OCD it's really just me playing and having a bit of fun so I won't loose too much sleep over it all.
Hopefully I'm learning too

You have a good perspective on this Danny, really good to see.

I hear far too many people saying 'close enough' or 'it's minute of deer' which is piss poor when you're taking an animals life.

I think the most important thing you are doing is minimising one variable that you have a high level of control over. Goodness knows in a hunting situation there are so many things to get sorted to get an animal on the ground with minimal suffering. Spending time getting to know your rifle well and having confidence that you can put the right bullet in the right spot is commendable.

Ahhh this is good clean fun Danny. Chase SD down to single digits then seating depth. Very close to the Berger method with VLDs that worked superbly in my 260AI. Going to chase seating depth now in my 308.

Originally Posted by Tikka7mm08

Ahhh this is good clean fun Danny. Chase SD down to single digits then seating depth. Very close to the Berger method with VLDs that worked superbly in my 260AI. Going to chase seating depth now in my 308.

One of the best groups I have shot with your old Ackley was with the Berger VLDs and new hydraulically formed brass with a less than perfect forming, (still had rounded shoulder) a tiny shoulder bump. Projectiles jammed into lands to ensure base is snug against bolt face. ES wasnt flash but the groups were.
Didn't worry too much about seating after that as it just shoots with acceptable ES when you do your bit it seems, wherever they're seated.
My blaser 260 ackley uses the exact same load. Also not fussy on seating. Same speed and group sizes with identical ES however the fired brass cannot be interchanged.
Shot both for the first time since before lockdown yesterday. Both shot way better than I expected as I havent fired anything but my pistols and shotgun since March. Wish I could shoot my pistols and shotguns as competently as I do my rifles after a long break.

Sent from my SM-T510 using Tapatalk

LOL, yes my old 260AI and my loss... the seating method halved the groups but they were already pretty good at .6"-.7"!

Originally Posted by Tikka7mm08

LOL, yes my old 260AI and my loss... the seating method halved the groups but they were already pretty good at .6"-.7"!

Yup, it is only used as a hunting rifle so not chasing ridiculous accuracy. However it seems to easily achieve it.

Sent from my SM-T510 using Tapatalk

Well.....had an absolute mare of an afternoon at the range.
Shot my seating depth ladder but due to sucking really bad at bore sighting I only got the last 2 rounds on paper.....
I should point out I thought I was hitting the paper my eyesight ain't that flash.
All my speeds were consistent however they were about 60fps slower than the charge ladder which I can't explain.
Either way I need to load up my seating depth ladder again and maybe a few sighters as well to make sure I'm on target as today's exercise was pretty much a complete waste of time.....completely my fault

Anyone know if the Caldwell chronos are affected by different lighting ? Ie: cloudy vs clear and bright ?

Originally Posted by R93

Yup, it is only used as a hunting rifle so not chasing ridiculous accuracy. However it seems to easily achieve it.

Sent from my SM-T510 using Tapatalk

I don't think I could sell a rifle that wasn't acccurate!

All optical chronographs can be affected by light conditions. Except maybe infra red back lit ones.
Litz also suggests that wind can set up resonance in the sensor arms which can affect results.

As far as not getting on target I have the view that, particularly with for eg hot 7mm throat burners, that every shot fired is one shot closer to a buggered barrel so I try to minimize firing extra shots for any reason. As such, I would have used your first shots fired when doing your ES and SD testing to at least get hits on a target. Maybe EC's method of not firing anything resembling a group at the ES and SD stage is valid with kinder calibres?

Originally Posted by zimmer

All optical chronographs can be affected by light conditions. Except maybe infra red back lit ones.
Litz also suggests that wind can set up resonance in the sensor arms which can affect results.

As far as not getting on target I have the view that, particularly with for eg hot 7mm throat burners, that every shot fired is one shot closer to a buggered barrel so I try to minimize firing extra shots for any reason. As such, I would have used your first shots fired when doing your ES and SD testing to at least get hits on a target. Maybe EC's method of not firing anything resembling a group at the ES and SD stage is valid with kinder calibres?

Quite right, even when testing charge weights in the future I will make sure that I am at least on paper, this rifle and scope are new to me and maybe I should have put a bit more time and effort into getting it sighted first.
I have now got it pretty close to right so lesson learned and at least it's a 270win and not a WSM or big magnum.

Originally Posted by dannyb

Anyone know if the Caldwell chronos are affected by different lighting ? Ie: cloudy vs clear and bright ?

If they're optical, then definitely. You can borrow my radar if you meet me at Sheffield tomorrow arvo. I won't need it for a while.

Sent from my SM-T510 using Tapatalk

Oh.....just seen you were testing a poo 70? Might have to reneg on the offer of the radar

Sent from my SM-T510 using Tapatalk