Designing the 2-diameter paper patch bullet.

[mherth]

Been trying to get my standard chamber 45-70 GM barrel to shoot PP well and am really thinking about a 2-diameter bullet. I’ve seen photos of bullets where the larger diameter portion is from about .125 or so up the shank to about a third of the way. Just what is the appropriate length and why? It seems like the shorter the better to get most of the bullet in the bore.