I'm going to offer counterpoint to Grizz... I suspect that new Hornady ammo won't make much difference except in narrow circumstances of real long range, especially when fired from a 20" 336. I'm just supposing, I've not tried the new (expensive) Hornady ammo. I just got a 30-30 in Nov. after years of using muzzleloader, and I love it. Killed three bucks with 150gr corelokt. One was a bad shot - he ran off, didn't get found til day later. Next one hit correctly, he went about five seconds and dropped. Third was a bang/flop.
I really like this 30-30 Marlin... sweet shooting, lethal, and it looks good, too.