I've found over the years that about any load will shoot into small groups at 25 yards. Indeed, most smoothbores will as well
and with only one sight, a fine sight being taken down the top breech flat.
Shooting at 50 yards or further out, is where the challenge and 'finding the right load' comes in.
I hardly think anything is different "up here" than "down there". 65gr. 3F, 75gr. 2F with my combination made for 2,240fps to 2,260fps,
identical accuracy of 1/2" 5-shot groups at 50yards. My loads were somewhat tighter fitting, that's all & the gun shot worse with reduced
powder charges when using LeHighValley lube. My .395"mould cast .398"x.398" and the .400" mould cast .400" x .400". I used both of these
balls with .019" pocket drill and with the 10 ounce denim I measured at .-0225", along with the railroad ticking I measured at .0235". 3/8" rifle's
rod worked just fine for loading. My .40 was a Goodoien barrel, with wide grooves narrow lands. My GM .45 barrel, loaded similarly, but with a
.445" ball, had grooves a bit wider than the lands, still good. It liked 75gr. 3F and 85gr. 2F - also making the same speed of just over 2,200fps.
Slower (smaller) loads did not shoot well at 50yards. At this level, both rifles seemed to shoot their best with the combinations I had tested with.
All of this was again, with LieHighValey lube - both the newer Track's recipe and the new "older" recipe. In my rifles, they shot identically.
With water based lube, spit or WWWF+ oil, both rifles would shoot the same with 10gr. less powder. I figured this was due to the water
based lubes not really being a very good lubricants. However, shoot well, they did.
If these loads seem high (I know they do) just look at the loads the chunk and plank shooters are using. Those guys are accuracy nuts and demand the
best accuracy from their guns. If 40gr. gave them the match winning accuracy in a .40, or 55gr. in a .50, do you not think they would be using 40gr. or 55gr.?
They do not as those loads will not give them the accuracy they demand and need to be competitive. Just to be competitive demands bigger charges. Just
shooting offhand so if doesn't matter? Yes it does - take you 'accuracy' capability, then add to the outside of that on 2 sides, the group size your rifle is capable of at that
range That is the smallest group you can shoot at 50yards.
If you are capable of shooting 2" offhand at 50 yards but your rifle is capable of 2" (5shots), your group could be about 8" for 5 shots.
If you are capable of shooting 2" offhand at 50 yards but your rifle is capable of 1/2"(5shots), then your group could be about 3"for 5 shots.