Bullet Mold modification.
Years ago I saw a manual put out by the Naval Ordnance Station in Indian Head, MD, that showed images of minie balls in flight that were captured by electronic flash as they tripped a trigger wire. A tad too much powder and they actually bell out at the base as they leave the barrel, the resultant drag negating any gain in FPS. They reminded me of a badmitton birdie.
The bullets I had been casting with my Lee mold had very thin skirts and I suspected my bullets were doing the same thing as they were all over the target with heavy loads. Figuring I had nothing to lose, I removed the cone from my mold that forms the cavity in the middle of the bullet, attached the cone to a high speed drill and carefully ground down the diameter to about 2/3ds its original width and then re-pinned it to the mold. Voila! Thick skirted bullets that actually allowed me to use 90 grains of powder and 3 shot groups that form a cloverleaf at 50yds.
I use 90 grains of Pyrodex in my T/C Hawkin and 30 years later with these improved bullets can still nail a tin can at 80 yds if the sun is bright.