Stupid calculators - years ago a buddies t/c contender shot 180gr for piggy's better than just good ,and they were round nose speer bullets. I tried a few loaded for my 308 my then new 788 remmy and it to shot them as well as 150 grain sp. It to has a 1-10 twist barrel just like the t/c 30-30. It might be hard to find a factory load for the 30-30 in 180gr. Not sure I have seen any. Like covered, might not feed in a marlin.