Reloading: A look at the Big Picture

[mikecr]

There is a couple ways to see it.
Changing seating does likely change optimum powder load. By a little no doubt.
But changing powder does not affect optimum seating. Why would it?
I ran Berger's test to find best coarse seating with 3 different powders in 26wssm. 139Laps consistently came in at 8thou OTL.
But when I changed bullets, the whole thing changed, going from 139Laps to 140VLDs changed where optimum seating was. For me, the VLDs preferred 37thou OTL.

Optimum Seating has nothing whatsoever to do with powder, or powder load. It's about the bullet bore interface. So it makes no sense to even think about powder until optimum (or very close to optimum) seating is established.

Another way to see it; with a good barrel you can double group size with big seating adjustments.
But, you cannot double group size with powder. No way.
This indicates that seating is coarser of an adjustment than powder.
When you calibrate anything, you adjust coarse 1st, then fine. And there is no adjustment finer than a kernel of powder.

 

[GetReal]

There is a couple ways to see it.

I like it. Thanx.

 

[big5ifty]

Powder first or seating first, you can get to the same result.

Whichever gets you right in the lowest number of iterations is better.

 

[big5ifty]

... once you've settled on a searing depth, it should hold for the range of powder charges e.g. from 24.0 grains to 26.0 grains.

Consider that if this is true, then it effectively makes powder charge a largely irrelevant factor, because the load data powder charge range between minimum and maximum loads is not much more than ten percent.

If seating depth holds for a 10 percent powder charge change, then you should be able to pick any powder charge in the load manual and provided you keep the seating depth the same [ after finding optimum seating for a charge ] , get the same accuracy.

Test it. Make sure it does. What should is not always what is.

To my knowledge, this is never the case.

 

[GetReal]

Consider that if this is true, then it effectively makes powder charge a largely irrelevant factor, because the load data powder charge range between minimum and maximum loads is not much more than ten percent.

In the video above (linked by another poster) , Brian Litz said in your heavier barrels, seating depth has FAR greater an effect on group size than powder charge. (Obviously, powder charge has SOME effect. But seating depth is teh coarse adjustment, and powder charge is the fine tuning factor)

In this 6mm example, powder range is about 2 grains btwn min and max - about a 10% change and a difference of maybe 150 - 200 fps.

I don't claim to understand everything Litz said, but I have no problem admitting he has forgotten more than I'll ever know.

 

[big5ifty]

I don't claim to understand everything Litz said, but I have no problem admitting he has forgotten more than I'll ever know.

If you try what he says and it works as he says, then it's good advice.