First off welcome to the forum.

You have a good rifle. But I will state that I do not recommend shooting roundball out to 150 yards although they will do it. Conicals do not lead up the bore as much as you might think. I shoot conicals out of mine all the time and with a bore brush and some solvent can clean up anything that might be in there.

Some of the 1-48 twist barrels shoot powerbelts very well. Even sabots. So all you can do is experiment. If you want to shoot powerbelts, many suggest a load of 80 grains of power. If you can place that powerbelt, conical, sabot, even a roundball, it will still do the deed out to 150 yards. You might not get a drop and flop, but there is the potential.

The .54 caliber barrel you mention is a good barrel. And one of our members demonstrated what a .54 caliber roundball can do on a elk at long range this year. I shoot a lot of Renegades. They are one of my favorite rifles. If you wanted you could go to a 1-28 twist and shoot sabots. Then you have a scoped rifle that is as accurate as any inline with a sabot. I also have a 1-28 barrel and I shoot a .58 caliber 1-70 twist and it is a very accurate rifle with a 110 grains of powder and a roundball....