bronko - here's a link you can go to to check these out:
http://www.hpmuzzleloading.com/MMP.html The article at the bottom of the page is all about the sub bases.

I'm guessing that cayugad used the sub base under the ball-et to prevent damage to the rear of the ball-et and affect accuracy. Maybe he'll respond when he comes back online.

cayugad: Where do you get the 270 grain ball-ets? I ordered some 245's from Cabela's, but they don't have the 270's.

Good Luck

IM jaybe