You haven't told us what kind of rifle or single shot pistol you are loading for.
With my old 30-30 Marlin (1952) with it's tight chamber I have to really watch the shoulder on my cases. I have to full length resize mine and bottom the dies out to the shell plate or I can't close the lever the whole way and the trigger won't pull. Mine is headspacing on the shoulder instead of the rim, it has to be short chambered, but you can do that either way.
If you think your accuracy should be better than it is, fire form some factory loads and experiement with the shoulder length instead of using the rim,- but only a few thousands of an inch on the shoulder could keep you from being able to pull the trigger.
I don't know what the new Micro-groove riflings are like to load for as mine has Ballard riflings. The only other 30-30 I have is my '46 30WCF Win 94. I'm a little behind the times with my rifles and plan on staying that way.
I use sierra 150 round nose, and 30 gr. of IMR 3031 and use Horn spray lube. Redding dies and Single stage all my rifle loads. As said above, watch your trim length and don't cheat on the OAL or you will have a jammed up rifle. Bolt actions, you can usually jam them in if they are really close but lever actions aren't as forgiving.