40 years ago, I loaded and shot T/C Maxi Balls in both my 50 and 54 Hawken rifles. I bought the boxes with 20 bullets, never cast them. I assume you are slathering the bullets with lubricant? I always used Wonder Lube back then. If memory serves me correctly, once started with a short-starter, the bullets could be sent home with minimal ramrod effort. They did not slide down the bore unassisted, but very little pressure was needed to send them home with a ramrod.
If casting them now with that mold, I would be casting in PURE LEAD to allow proper fitting in the bore, and allowing for proper bump-up when the large powder charge is ignited. There is AMPLE space for lubricant to work its magic down the tube when fired. The Wonder Lube was (still is) a rather soft lubricant which remained in its original state during a hunting session due to normally cold weather. Wonder Lube would NOT work too well when the outside temperature is 98 degrees in the summer. It would tend to liquefy and saturate the powder charge. Using a different lube like say Confederate Lube, may not be as good as the Wonder Lube consistency, but I am guessing here.
So.....were I to cast some today with that mold:
- I would see that they were about .001" greater than BORE diameter to ease their loading.
- I would cast them in PURE LEAD to allow for ease of loading AND even more importantly, to allow for bump-up to groove diameter upon firing.
- I would slather them in Wonder Lube as they were designed for.
Hope you get this figured out and get that rifle shooting fine with them.
With rifle in hand, I confidently go forth into the darkness.