It would probably shoot both but with the roundball you could not push it too hard. I would suggest a nice maxiball with a wad under it. That twist should produce some excellent accuracy. I bought a .50 caliber CVA Stalker Carbine with a 1-32 twist and it has been a most pleasant surprise with 80 grains of Goex a wad and a maxiball. It is a real shooter. I have not seen how hard I can push them because 80 grains and a maxiball would be all that the rifle would need for me....