Hi Big Mike,
Do yourself and your 1:48" twist T/C muzzleloader a big favor and to go the Precision Rifle Custom Muzzleloader Bullets webiste and look at their bullets for your .45 caliber muzzleloader.
Precision Rifle has the best **** muzzleloading bullets period --- especially if you are looking for streamlined bullets for long range shooting. Look at their Dead Center, Extreme Elite and Double-Saboted bullets.
My with 1:48" twist T/C .50 cal Hawken, I used an Extreme Elite bullet and the mule deer I shot dropped in its tracks and rolled down the hill to my feet. Wow!
For long rang shots at deer with you .45 cal T/C with its 1:48" twist barrel, you can use a saboted bullet at fast velocities if you choose one of Precision Rifle's Custom muzzleloder bullets.
For your .45 cal muzzleloader look at these bullets:
Dead Center --- 175 gr to 240 gr
Extreme Elite --- 240 gr to 260 gr
Probably your best choice of bullet for long range shooting at deer with your .45 cal is a 195 gr Dead Center bullet. This is a .357" diameter lead bullet in a sabot for .45 caliber that is simply deadly on deer at long ranges. The sabot is rated for high pressures so you can use max powder loads.
You can always call Precision Rifle at 1-8778-BULLET and see if they now have their Double-Saboted bullets available in .45 calibler.
Precision Rifle is on the cutting edge of muzzleloading bullet technology and their bullets have won the World Muzzleloading Championships.
Look at the Ballistics tables on Precision Rifle's website and you'll see that their .45 cal muzzleloading bullets pack plenty of killing power at long ranges.
Don't let anyone ever tell you that you can't shoot saboted bullets in your 1:48" twist T/C muzzleloader. I used my 1:48" twist T/C muzzleloader with saboted bullets and get superb accuracy at long ranges, plus I shot a nice mule deer.