I've starting casting some rounds for my Airforce Texan with good results. Thought I might share.

Lyman "collar button" 145gn

195gn Diabolo! pictured here beside jsb in .177 and 25 cal king for comparision

Mold by Jeremy King @ ~http://www.africanairordnance.com/424818176
You can order multiple bases to change pellet weight and
Jeremy was excellent to deal with, he even included a sizer that you can us in any standard drill press.

Lyman "collar button" 145gn

195gn Diabolo! pictured here beside jsb in .177 and 25 cal king for comparision

Mold by Jeremy King @ ~http://www.africanairordnance.com/424818176
You can order multiple bases to change pellet weight and
Jeremy was excellent to deal with, he even included a sizer that you can us in any standard drill press.