1. Don't overlube.
2. Full length resize.
3. Trim, every time.
4. Deburr & chamfer, every time.
5. Use only bullets with a cannelure.
6. Find the load and bullet that works for your rifle and stick with it.
7. Finish with the Lee Factory Crimp die or an equivalent.
The list above will save you from crumpled shoulders and other gremlins that pestered me when I started loading this cartridge a little over 35 years ago. Sierra's 150 grain soft-point has given best accuracy in the vast majority of 30-30s that passed through my hands. It's now the only jacketed 30-30 bullet I buy.Tried all the powders reported to give best velocity, etc, H4895 is now the only rifle powder I buy.
“Nine-tenths of tactics are certain, and taught in books: but the irrational tenth is like the kingfisher flashing across the pool, and that is the test of generals. It can only be ensured by instinct, sharpened by thought practicing the stroke so often that at the crisis it is as natural as a reflex.” ~ T. E. Lawrence