The 500 RN carries best for long range. However I found the recoil is excessive and gave up on it quickly. The Lee 405 HB is hard to beat. Pick up a copy of Spence Wolf's book on reloading the Springfield TD. Great read and lots of really good info.
Also, spend some time on this site as well. Al Frasca also wrote a great book on these guns.
https://www.armscollectors.com/trapdoor/In my 1880 Carbine I cast 20-1 alloy with .462" sizer using a soft BP lube even though I shoot smokeless loads.
