Changing brand of brass on an established load

[mtmojo]

I was changing to a different brand of brass, I had a load worked up that didn’t cross over to the newer brand. I’m guessing the case capacity is different resulting in different pressures. So, I figured I’d do a small ladder test to match the same speeds and then I should be close to the same pressures and should probably start seeing similar groups. Backing off .5 and my speeds matched back up.

In doing this testing I found another interesting caveat. I accidentally loaded up several rounds a little deeper than my current load. I put a few more together to have a 5 round test group. I got the following results:

2.644” 2.647”

SD 4.5 11

ES 9 24

2941 fps 2928 fps

Does a bullet like a certain amount of jump or is it really a pressure / speed that it prefers? Can one offset the amount of powder by simply adjusting the seating and get the same speed results? (in small degress that is) Is a ladder test by using a set amount of powder and adjusting the seating depth a viable option compared to a set seating depth and varying the amount of powder? Has anyone encountered this as well?

 

[wind gypsy]

I'd bet my paycheck all you're seeing is random distribution from small sample sizes rather than a 0.003" seating depth change causing 13 FPS increase in avg MV and 2.5x higher ES.

 

[BossGobbler2024]

Some bullets do like more of a jump but .003 jump difference is not likely to be that much different.