Hi 10851Man!
After getting a Lee mold for conicals, I justed tested them and compared with Round balls. I have Pietta Army 1860 cal 44.
I tested RB cal 454, and Lee Conical 450-200.
I tried both types of ammo in the same manner - starting with 24 grains charge and then after each mag, reducing the charge down to 15 grains.
I tested from a rest bench.
My goal was to achieve best accuracy possible, so my finding is following:
1. Round Balls are more accurate then conical - when compared to conical in every different black powder charge.
24 grains load - RB better accuracy
21 grain load - RB better accuracy
18 grain load - RB better accuracy
15 grain load - RB bettrer accuracy, and smallest group at 25 yards (about 3 inch group // conical made 5 inch group)
2. The best accuracy was when getting down to 15 grains of powder.
3. This one may answer your question: I have achieved the best accuracy with conical (200 grains) and round ball (140 grains) with the SAME charge of 15 grains. Ball performed better at 25 yards.
This may be the reason why Pietta manual will advice the same load for different type of projectile.
One more note: I also sent the msg to Pietta factory asking for preffered type of projectile - and they replied they reccomend onli a LEAD ROUND BALL 451 or 454. My test proved them right.
I dont have chronny - so I dont have any data to compare the speed of two different projectiles.
Do me a favor: When testing your Pieta 36 cal, please let us know the results. I am especially interested in accuracy, for target shooting.
Also, pls let us know - what Pietta gun do you have: Remingtom Navy, or Colt Navy?