Long range load development at 100 yards.

[Brians356]

I’m thinking 8, 9, and 10

I don't subscribe to this method, but I understand the concept. In that context, 8-9-10 shows promise to this jaundiced eye. Now, move on to the real testing, starting there.

PS This is not the method for which Erik Cortina started this thread.
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[lazyMlazyK]

PS This is not the method for which Erik Cortina started this thread.
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Sorry, thought that was obvious. Seemed like a good place to put it though as it relates SOMEWHAT to his method.

 

[Brians356]

Sorry, thought that was obvious. Seemed like a good place to put it though as it relates SOMEWHAT to his method.

There are no fewer than 37 threads with "ladder" in the subject, in 2018 alone (!), any of which would probably be more apropos. Plus this thread is now up to 104 pages. Yikes!
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[seymour fish]

Shot the .22-250 at 322 yards last night. 13 rounds, starting at 36.3 gr. H380, ending at 39.9 gr. Worked up in 0.3 gr. increments. Bullet was Nosler Varmageddon 55 gr. flat base ballistic tip p/n 17240. Was not shooting groups, just a ladder. What are your thoughts? I’m thinking 8, 9, and 10, or 11, 12, and 13 look like nodes? Chrono wasn’t working or I would have velocities to add here as well.

8-9-10

 

[Brians356]

Also FWIW, Erik Cortina himself hasn't commented here in over three years.
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[Ned Ludd]

BTT

 

[dstoenner]

German Salizar is absent as well.
What to know why?

OK, I give

David

 

[Ccrider]

Wow. I guess some people don’t understand the irreplaceable value of sage advice.

 

[Kurt Blasser]

Shot this yesterday. Would like comments regarding which load would be best. Shot Cortina technique with 200.20x, Varget 43.0 through 44.8 in .2 gn increments, 30 inch 1-10 twist barrel. Bullet seated .020 off jam.

 

[oldduc]

Shot this yesterday. Would like comments regarding which load would be best. Shot Cortina technique with 200.20x, Varget 43.0 through 44.8 in .2 gn increments, 30 inch 1-10 twist barrel. Bullet seated .020 off jam.

I like #8. It's the flattest.

 

[mikeeg02]

Shot this yesterday. Would like comments regarding which load would be best. Shot Cortina technique with 200.20x, Varget 43.0 through 44.8 in .2 gn increments, 30 inch 1-10 twist barrel. Bullet seated .020 off jam.

I would take 44.2, and 44.8 and shoot them again at 200, and then fine tune seating depth on whichever shot better.

 

[Hollywood]

Shot this yesterday. Would like comments regarding which load would be best. Shot Cortina technique with 200.20x, Varget 43.0 through 44.8 in .2 gn increments, 30 inch 1-10 twist barrel. Bullet seated .020 off jam.

43.2-43.6 looks to have the least vertical displacement. I'd explore 43.4 next. I marked the group centers to make it easier to see.

 

[daniel brothers]

the hotter it shoots... better the groups...44.8 or better

 

[Hollywood]

the hotter it shoots... better the groups...44.8 or better

At this point in the testing you are not looking for the smallest group size. First is the least group verticle dispersion in a row then the following seating and revisiting of powder charge will shrink the groups.

 

[BCBRAD]

I did not read all the 105 posts.

What a friend and I do is employ the LabRadar and Quickload to find a powder charge that is OCW and OBT at the same time.

With Quickload accurate velocities are a must, program doesn't work with out.

So getting a good load goes like this:
- decide on magazine length or 10-15 thou of rifling for the COL
- input all parameters as accurately as possible to the program
- through modelling you will find the best powder for components used
- you will see if the modeled load is close to an OCW and OBT
- load up 5 rounds and shoot for velocities
- adjust powder charge to reflect the predicted velocities
- if all your inputs are correct the next set of 5 will be at predicted velocity
- This load will likely the best your platform will do.

We have been getting 0.3 moa's at 330 yards and 0.4's at 540 yards, 5 shot groups. 10 shot groups will go high 0.5's to low 0.6's at these ranges on a day the shooter is up to it and with good conditions.

1000 yards targets are generally up to 25% larger as compared to those at 330 yards. This puts us into the 1/2 moa zone on a good day but rarely over 1 moa on a challenging day. This is a reflection on shooting skills.

The QL operator must have knowledge of internal ballistics to operate the program successfully. All QL does is the math.

This and attention to your weights and measures will get you there.

The rifles we use are for the most part rebarreled Tikka T3's and hunting rifles with aftermarket barrels and some factory rifles. Definitely nothing exotic.

 

[Hollywood]

I did not read all the 105 posts.

What a friend and I do is employ the LabRadar and Quickload to find a powder charge that is OCW and OBT at the same time.

With Quickload accurate velocities are a must, program doesn't work with out.

So getting a good load goes like this:
- decide on magazine length or 10-15 thou of rifling for the COL
- input all parameters as accurately as possible to the program
- through modelling you will find the best powder for components used
- you will see if the modeled load is close to an OCW and OBT
- load up 5 rounds and shoot for velocities
- adjust powder charge to reflect the predicted velocities
- if all your inputs are correct the next set of 5 will be at predicted velocity
- This load will likely the best your platform will do.

We have been getting 0.3 moa's at 330 yards and 0.4's at 540 yards, 5 shot groups. 10 shot groups will go high 0.5's to low 0.6's at these ranges on a day the shooter is up to it and with good conditions.

1000 yards targets are generally up to 25% larger as compared to those at 330 yards. This puts us into the 1/2 moa zone on a good day but rarely over 1 moa on a challenging day. This is a reflection on shooting skills.

The QL operator must have knowledge of internal ballistics to operate the program successfully. All QL does is the math.

This and attention to your weights and measures will get you there.

The rifles we use are for the most part rebarreled Tikka T3's and hunting rifles with aftermarket barrels and some factory rifles. Definitely nothing exotic.

That is one way to do it but that is not what this thread is using. You don't need to read all 105 pages of posts just the first one to better understand the Cortina method. It is a little different but works well if followed.

 

[daniel brothers]

My point is that the hotter loads shooter tighter groups as these groups pivot around the crosshair center point, and the 44.8 is the tightest group at the 4 o'clock area of the crosshair... and if he shoots 45.0 and even better... then they MIGHT also be tight groups and hang in that same area... if so... then he has a winner without much seating depth adjustment needed... if any at all.

 

[BCBRAD]

No argument with the Cortina method.

It is a method to adjust pressure, therefore velocity, to find a node.

The tools we use are QL, Labradar, a scale that resolves to 0.02gn to get similar results.

We have a range that is 1500 yards, it is lightly used so we spend more than average time practicing .

 

[JimSC]

If you look at the averages of 43.2 - 43.4 there is only a 6 FPS ES. I would load 25 rounds using 43.3 as a charge weight and seat them .15 longer and do a little fine tuning at the range with a Lee handloader and my seating die. Start with the base to ogive that this test was ran at and start shooting + or - .003 until you get a flyer then go in the other direction until the same, repeat until satisfied you have found the best length. Obviously you must be able to call your shots and be honest with yourself on your abilities but it has helped me tremendously since I adopted it last spring

I do wonder about the validity of the three shot velocity tests however. In a rush to find a load for a 300 yard match I did a 3 shot test. At 40.0 - 40.3 gns I had some nice .2 and .3 groups but with high ES and SD #'s. At the same time I had low SD and ES at 41.5 - 41.8 but groups increased to over .5. Since the match was 300 yards where the ES effect would be low I ran a 15 shot test on the low end load that shot in the double digits with the earlier shot test and came up with a 10 FPS SD and a 30 ES that shot well under a MOA spread. At 41.5 to 41.8 the ES and SD hardly changed at all and group sizes were a bit over a MOA.

All rounds were with new fresh from the box Lapua cases which had only been FL resized for conformity

 

[Kurt Blasser]

If you look at the averages of 43.2 - 43.4 there is only a 6 FPS ES. I would load 25 rounds using 43.3 as a charge weight and seat them .15 longer and do a little fine tuning at the range with a Lee handloader and my seating die. Start with the base to ogive that this test was ran at and start shooting + or - .003 until you get a flyer then go in the other direction until the same, repeat until satisfied you have found the best length. Obviously you must be able to call your shots and be honest with yourself on your abilities but it has helped me tremendously since I adopted it last spring

I do wonder about the validity of the three shot velocity tests however. In a rush to find a load for a 300 yard match I did a 3 shot test. At 40.0 - 40.3 gns I had some nice .2 and .3 groups but with high ES and SD #'s. At the same time I had low SD and ES at 41.5 - 41.8 but groups increased to over .5. Since the match was 300 yards where the ES effect would be low I ran a 15 shot test on the low end load that shot in the double digits with the earlier shot test and came up with a 10 FPS SD and a 30 ES that shot well under a MOA spread. At 41.5 to 41.8 the ES and SD hardly changed at all and group sizes were a bit over a MOA.

All rounds were with new fresh from the box Lapua cases which had only been FL resized for conformity

Same can be said for 44-44.2, only 6 fps. I'm concerned the lower loads might not be quite hot enough. Somewhat worried 44.8 to 45 getting kind of hot. I've seen some comments that 2630-50 about the right area for the 200.20x.