Originally Posted by AtownBcat
I read the article by Jerry on load development and i had a quick question. If you find the sewwt spot as far as the powder charge goes and then play with seating depth does it change the "sweet spot" on the powder. I just figured that by changing the seating depth you were changing pressures therefore affecting the amount of powder you would need. It seems the more i read the more it becomes apparent that the different combinations of powder/seating depth/primers/bullets are endless and you could spend forever looking for the "perfect" load.
In short, no it doesn't!
What you are changing is the barrel harmonics, which is detrimental to accuracy. The powder is still performing at it's optimum, very little pressure/velocity changes will result by changing seating depth. Although if you start at a COL that is .050" off the lands, and you change it to be .005" off the lands, pressure CAN increase, but not always. It's wise if doing this to back off and work back up to the previous load.
Also, I will add, that the powder that gives the highest velocity with the least pressure is generally the most accurate because it will have a wider 'node'.