Probably my favorite bullet for the 30-30 is Lyman's #311291 designed way back in 1905. That bullet with a BHN hardness of 12 loaded to full power is not only accurate in a Marlin 336, but in two Winchester M94s, two Winchester M64s and a Winchester M54. With that bullet, I have killed 15 deer with no complaints from the deer. Another bullet that I tried was the RCBS #30-180-FN which casts a 190 gr. bullet in my alloy. Loaded to full power it duplicated the .303 Savage and thw two deer shot with that bullet also gave no complaints. In fact, I think it just might be a better killer based on the two deer I used it on.
I have two Lyman #31141 molds (Current number is 311041 it Think) and a clone of that bullet by NEI. To date, I have not been able to get any of those bullet to group worth spit in any of my rifles. That does not mean it's a bad bullet, it's just I can't get it to shoot in my guns. Too many people have stated how good it shoots in their guns so the only way to find out is cast 'em and shoot 'em.
I also have that Lee 170 gr. bullet and it shoots almost as good as the #311291. The best way to see if a bore riding bullet will shoot well BTW is to insert one nose first into the muzzle of the rifle. If there is any play or wiggle room at all, odds are it won't shoot well at all. You want a tight fit and I prefer that the bullet be slightly engraved by the rifling, especially in the Micro-groove barrels. I don't shoot the Winchesters much any more as my 7.5 decade old eyeballs are not up to the task of seeing the iron sights. The Marlin on the other hand will do a nice 1.5" group on average with my cast loads as long as I do my part.
One thing I do know and that is the 30-30 and cast bullets were meant for each other.
Paul B.