Watch this youtube video and read all of the the replies to the questions.
Sighting in a new Buckstalker with a 300 grain bore size conical, 100 grains of pellets, took 4 shots to sight in,
Ended up obtaining 4 inch groups at 100 yards with only a quick swab between shots.
Your conical is heavier, but the starting load may not be much different.
He was using 100 grains of 777 pellets (2).
I would start with 90 grans of the 3F 777, and increase 10 gains (or even decrease 10 grains) to see how it groups.
Just get it on a paper target at short range at first.
Your heavier conical may produce more felt recoil, so don't go overboard with the powder.
100 grains of 3F 777 equals about 115 grains of Pyrodex 2F.
No need to over-compress the powder too much because doing that can cause erratic velocities
But make sure to seat the conical on top of the powder charge with at least light to moderate pressure.
Switch to a lighter bullet if your results are not satisfactory, or if the felt recoil is too heavy.
One of the replies mentions the conical that he is using is a Traditions Full Bore Bullet 300 grain No Sabot Required Model #A1820.
It looks just like a Hornady FPB except those come in 2 sizes - 300 and 350 grains.
Hornady FPB info: https://www.hornady.com/muzzleloadin...zzleloading#!/
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