I know so many deer and hogs that have been lost with powerbelts that IMO it should be your last resort. Agree with RobertR. Try the Barnes TEZ sabots. I can easily get a second one down the barrel after shooting at game without swabbing or putting bore butter all over everything. Get great groups with them as well. Good luck!
Like Robert above I have a really old Knight .50 cal. I have always used Barnes 250gr Expander Mz bullets and the black sabots that comes with the box. The bullets are .451 dia. I can shoot my gun as many times as I like with minimal patch every few shots. I don't even know what bore butter is and have never used any lube to load my gun.