Seating depth tuning- need suggestion

[Bang4theBuck]

I've got a full custom 7mm Sherman Max rifle that I'm developing a load for with Berger 195 EOL bullets with. I've got the velocity numbers very tight at this point at 2870 +/- 4 fps. I am still seeing consistent vertical stringing in the load. My groups are .725- .900., pretty consistently across over a full grain if powder. The velocity node is pretty wide. The low was 2858 and the high was 2875 across .8 grains of powder delta. I'm loaded right in the middle of that node, and the groups are all significantly more.vertical than round, or horizontal.
I am already jumping the bullet .080" of an inch, and that gives me one cartridge diameter of bullet engagement into the case (my self-imposed minimum).
Looking for advice on how much I should vary the seating depth on the next round of tuning for this bullet of this size and weight.
.005" increments?
.010" increments?
.030" increments?
Other?
Thanks in advance for your thoughts.

 

[Rick Richard]

You're going to get varying opinions, but I follow the Berger suggested method. With that said, all of rifles like something between, .010 to .030. Good luck

 

[FEENIX]

You're going to get varying opinions, but I follow the Berger suggested method. With that said, all of rifles like something between, .010 to .030. Good luck

This!

 

[Koda_]

Looking for advice on how much I should vary the seating depth on the next round of tuning for this bullet of this size and weight.
.005" increments?
.010" increments?
.030" increments?
Other?
Thanks in advance for your thoughts.

Eric Cortina suggests .003" increments because he finds seating depth nodes about .006" wide.
Ive moved in .005" increments for simple math and its worked for me.

Vertical stringing sounds more like a different problem, barrel heating or large ES maybe?

queued up to his notes on seating depth nodes:

 

[Rick Richard]

Eric Cortina suggests .003" increments because he finds seating depth nodes about .006" wide.
Ive moved in .005" increments for simple math and its worked for me.

Vertical stringing sounds more like a different problem, barrel heating or large ES maybe?

queued up to his notes on seating depth nodes:

I believe those are movements from his initial starting point, which is .030 off Jam as he illustrates in a video for not chasing the land

Now, I see where you posted his video. My bad for not looking closer.

 

[Koda_]

I believe those are movements from his initial starting point, which is .030 off Jam as he illustrates in a video for not chasing the land

Now, I see where you posted his video. My bad for not looking closer.

Correct, I set the video to start exactly at the moment he discusses seating depth nodes. About a 15 second watch to hear his comment on that.

The video covers the broader subject of chasing the lands but he touches on the smaller subject of seating depth nodes which has been useful for me finding my own. When I was first learning this I chose large jumps like .020" and saw no change but it turns out I skipped right over the node.

 

[birddog 68]

It sounds like you are fairly close to what your rifle likes. I usually go in .020 increments to find the neighborhood it likes and then do +\- .005 increments for fine tuning.
Everyone has their preference on how to get to the same place.
I will add that I had a Ruger 280 that shot great using the 168 Berger and they were at over .100 jump.

 

[Bang4theBuck]

Eric Cortina suggests .003" increments because he finds seating depth nodes about .006" wide.
Ive moved in .005" increments for simple math and its worked for me.

Vertical stringing sounds more like a different problem, barrel heating or large ES maybe?

queued up to his notes on seating depth nodes:

Thanks for taking the time to que this up. I know the issue isn't with barrel heating up. It was a cool day, and only 3 shot groups woth.time between to cool, and as I said in my initial post, I've got the ESs down very low (sub 10 fps)

 

[BigDon]

I believe those are movements from his initial starting point, which is .030 off Jam as he illustrates in a video for not chasing the land

Now, I see where you posted his video. My bad for not looking closer.

So that means, if I'm following the math properly, the start point is about off contact to about off. Gee - I think this is where Hammers also like to start.

 

[Dean2]

If you are seeing vertical with that little ES, and it isn't heat or a carbon ring, then I would be checking neck thickness and tension. I have not seen jump eliminate vertical, but others may have.

 

[Rick Richard]

So that means, if I'm following the math properly, the start point is about off contact to about off. Gee - I think this is where Hammers also like to start.

I shoot my Hammers from .020 to .200. It doesn't make that much of a difference with them.

 

[Koda_]

Thanks for taking the time to que this up. I know the issue isn't with barrel heating up. It was a cool day, and only 3 shot groups woth.time between to cool, and as I said in my initial post, I've got the ESs down very low (sub 10 fps)

How many rounds did you fire to measure your ES?

 

[Bang4theBuck]

If you are seeing vertical with that little ES, and it isn't heat or a carbon ring, then I would be checking neck thickness and tension. I have not seen jump eliminate vertical, but others may have.

Well, I suppose that it it possible that there is a problem with the necks. Based onnthe feedback I've gotten so far, I loaded the following for the next round:
2.350" = .082" off lands
2.335" = .097" off
2.320" = .112" off
2.305" = .127" off
2.290" = .142" off
2.275" = .157" off

I'll report back with my results.

 

[Bang4theBuck]

How many rounds did you fire to measure your ES?

I only fired 3 shot groups, which isn't a great sampling, however, over the course of 6- 3 shot groups, which was 1.2 grains of delta from high to low, there was only 45 FPS delta from highest to lowest, so I feel that at 100 yds, these delta don't produce 3/4" differences in elevation, so I deemed the data relevant.