At our local CBA matches I’ve been experimenting with the adjustment feature on my breech seating tool. How far into the throat area does it push the bullet into place?

The Randolph book, Schuetzen shooting for the new shooter, suggests adjusting the tool so the start of the barrel land marks are about halfway onto the bullet’s (lowest) base band. I messed around with doing that and even farther down on the base band. I eventually settled on having the barrel marks just short of the base band. I recorded the distance the “seating plug” extends beyond the case mouth in all of the trials. 

The judgement criteria was 100-yard 10-round group size. You know the old adage…almost anyone can shoot a nice 5-round group but adding five more shots can cause some of us “severe angst”, even ruining the group.

However, variables such as barrel characteristics and load variables like bullet size, design and alloy, powder type and weight, primer details, etc. will impact results. And the bench set-up, ambient conditions and of course the SHOOTER, are also influential.

FWIW

Tom

Being a dyed in the wool neurotic jibbering idget, I have 5 32-40 breech seaters for my 4 high walls.  All are set to different seating depths.  I manage to have that many since I keep the ones that have manufacturing defects. I think my average is one mistake for every 6 I make for sale.  I typically adjust so there is about 1/4 of the base band engraved.   

Jack.

I used to be a jibbering idiot, but one day I forgot the hex key needed to adjust my seater. I shot better than usual since I didn't need to concern myself about maybe improving with a different setting.

Hmm.  Now I understand a little bit more about myself 

One of the more interesting things I've read on breech seating depth is this little bit from the CPA web site on the 32-40 cartridge.   

"Our rifles are taper throated from .322 to .314 in about 7/8” length, and a matching bullet can be easily seated perfectly and without distortion.  Seated this way in the taper throated chamber, the bullet will have rifling marks its full length except for the base band."