It's not uncommon for the bores of modern in-line muzzleloaders to vary as much as .002" to .003" from rifle to rifle. Most .50 caliber bores today will run .500" to .501". However, a lot of production run barrels will go .502" to .504" - and finding the optimum combination of bullet-sabot fit with those bores can be difficult. Here is a look at how inexpensive and easy to use Teflon plumber/thread tape can be the solution.
http://namlhunt.blogspot.com/2011/07/tighten-up-sabot-bullet-fit-for-tighter.html
