My father started building BP rifles in the late 1950's. He made his last one shortly before his death in 2005. The vast majority were in .45. He considered it the best all around caliber. As a matter of fact, when I showed up with a .50 cal in my early 20's he asked if I was going to take up hunting elephants. I literally grew up with black powder and most of my rifles have been .45. It's economical in both powder and lead while producing reliable killing power. What more can you ask for? Walk into my den right now and you may notice that the one and only rifle is a flintlock built in the 1960's. It's a .45. You did good.
John