Designing the 2-diameter paper patch bullet.

[flatsguide]

This is a very interesting read as I have been thinking about two diameter ppb’s for a while now for my Browning 45-70 bpcr. It is shooting 1.25” to 1.375” groups at 100 yds with ppb’s. On post 18, the belted groove diameter section of the bullet appears to be over one caliber long. Does it need to be that long? Was thinking that the groove diameter section in the neighborhood of .125” to .135” long would work. Seated in the case that far would give better powder capacity and the bore section being longer would give better bullet/bore alignment. Also the transition ring at the bore to groove diameter being much further back may contribute to better stability. Maybe with a short groove length band it may strip but they don’t with a bore diameter ppb’s. Also one might have better results with a harder alloy like 1:12 or 1:10. Would like to hear your thoughts on this as I may order one from Brooks. Also if .125”/.135” proves to be to shallow it might be possible to dial in the mold and cut the groove section deeper.
Beltfed is getting nice groups with his two diameter bullets.
Thanks Richard