Daryl-

Short slug -- I have the Lyman mould for the 12-gauge flat-point slug. I haven't run them in the rifle yet, but may do so some time soon. If so I'll likely make a different plug to somewhat shorten the hollow section in the tail.

That .684 ball mould you have sounds like a good in-between.
I'd like to buy a pound of lead ball from you!

Any way it goes, I have a feeling that this rifle is an accurate one.
Each time at the ranch lately has been short, and I haven't had the time to put a good part of a day to load testing and shooting, still each time out the rifle seems to be putting them into the same aggregate group.
The chronograph is still on the fritz, hopefully I'll get it sorted out right away so that I can report back with velocities.
This will come soon...

Cheers
Tinker