I tried this as a wad:dewey-1 wrote:The rear seal could be either an o-ring or a flexible flat disk attached near the back of the sabot. I initially considered drawing that it but decided to leave out. I will update the model to show a seal.
A 16 ga shotgun shell cartridge is about the right size for 3/4 in Type M copper barrel. With a rim OD of .815 inch, trim the rim to fit your barrel.
http://www.dave-cushman.net/shot/shotshellloads.html
Go with a pound of flechettes and 16 ga used shot gun shells.

( Very easy to make)
The cg was not far enough forward and it tumbled.
How do you keep the $8.95/pound Flechette centered as it is driven down the barrel?
BTW Good thread.
Thank you dewey-1 for your great ideas an drawings.
BoyntonStu