A real interesting device - thanks for the great photos.
I'm curous if you "lube" over your balls? If so, this would add another step after you install the cylinder and do the final seating of the balls. My only concern with using something likd this is that I might "forget" to seat the balls once I'd changed cylinders. I'm not being critical here . . I'm thinking about myself and how sometimes I could get distracted and forget to do it. I think they call it "senility"?
I understand your concept of using it as a "ball starter" and it looks like it would be slick for that. I'm wondering if you have a "regular" load that you use, could you measure from the seated ball to the face of the cylinder and then put cupped metal dowels, slightly smaller in diameter than the cylinder bores and slightly longer than the measurement from the ball to the cylinder face? I would think that you would "develop" a feel for when the balls were seated tight to the powder. I know that I am able to "feel" when the ball is seated when loading my revolvers. I also know though, that a short barrel with a short rammer can be very hard on the hands. I used to have a brass framed Navy Arms .36 round barrel sheriff type pistol that was hard on the hands when using the loading lever. I used to carry a short section of conduit to slide over it for added leverage.
Thanks again for the great post and photos and welcome to the forum! I hope you'll keep us updated on how this device is working for you and any improvements you might add! Thanks again!