I hunt with a T/C Encore 209x50 muzzleloading pistol and it's GREAT! Shooting a 300gr Hornady XTP/HP sabot with 100 gr of Pyrodex, you get 1550 fps and 1600 ft/lbs of energy - plenty for whitetail deer at 'close' range.

Looking at a ballistics table (which shows energy, speed, and bullet drop at various distances) will tell you what your effective range will be. This Encore, when sighted dead-on at 100 yards with that 300gr bullet, will have nearly 6 inches of drop at 150 yards, and nearly 16 inches of drop at 200 yards.

You can compensate for some of this by sighting in 3 inches high at 100 yards. Then, at 150 you'd only be 3 inches low and still in the kill zone. But you'd have to compensate for 13 inches of drop at 200 yards, so you'd have to hold the sights somewhere in the air over the deer's shoulder.

You can compensate further by using a lighter bullet like a 240gr. This bullet, when sighted dead-on at 100 yards will have 5 inches of drop at 150 yards and 14 inches of drop at 200 yards.

Again, by sighting in your 240gr bullet 3 inches high at 100 yards, you'd be 2 inches low at 150 and 11 inches low at 200. So for the long shot, you'd hold higher on the deer and could still have a shot in the kill zone.

As you can see, anything much beyond 150 yards relies too much on luck, due to having to hold high or over the deer. Also, the energy of the bullet beyond 200 yards is dropping below the point needed for a humane kill. And these cases are under perfect conditions.

You could of course sight-in better for longer ranges, it just depends on where and how you hunt. Living in Minnesota, you probably won't be taking too many 345 yard shots with a muzzleloading pistol. Whatever you buy, consult the ballistics table to find out the gun's effective range. Then you need to shoot and practice to determine YOUR effective range.