Lyman lists a load for a 420grain cast bullet for the 1886Win. and 1895 Marlin using IMR-4198. It doesn't get to 1800. IMR-4198 START 28.5grains 1267fps w/fiber wad over powder----MAX 41.5grains 1737fps.....or you could try this Reloader 7 START 40 grains 1493-----MAX 48.5grains 1828fps......and they show the RE-7 load running 3000C.U.P. less pressure than the 4198 at MAX. Might be something to consider. Loads listed in Lyman reloading handbook #47.