Plinking quality cast bullets is no problem at all!
You can buy bulk 405 grain and 350 grain cast bullets at the gun shows for about the same money as you can buy lead alloy, cast, and lubricate your own. The copper-plated ones work even better. I load to approximate .45-70 M1873 levels with 13 grains Unique, 35 grains IMR 3031, or similar loads using IMR 4895, IMR 4198, ect. These are starting loads in the loading manuals and safe in all models of .45-70 rifles. You can load hotter for your 1895 Guide Gun, of course, if you want to put up with the increased recoil.
Most ANY 350-405 grain cast bullet is suitable for casual shooting. All of the various RN and FN bullets by Lyman, Lee, or RCBS, etc are good.
HTH
John