I own and shoot 5 different MN. Three 91/30's , M39 and a Polish 44. Have shot 1000's of cast bullets through them. Lyman 311299's with mostly 4198. While I have only slugged a couple of the 91/30's my understanding is the Finnish bores are a little tighter than the Russian jobs. (M39- 309) I shoot 314's out of my Lee Enfields, and Russian MN's and Polish M44 and 311's in my 39. Have tried 2400 and 5744 but kind of settled on IMR 4198. The M39's have a reputation for being the most accurate. The easily windage adjustable front site is a real bonus in my opinion.