I have used Lee Loaders in .30-30, 6.5 Carcano, .38 Spl, .303 Brit, .45 ACP/AutoRim, .32 ColtNP, .30 Carbine.
My experience has been that case crimp I get with .30-30 has been good. But I do use the Lee hand case trimmer set for .30-30 and reload cases in batches that are the same trimmed length. My experience with cartridges fired in Marlin 336 has been little case stretch base to neck, but shot after shot brass will flow making the necks gradually longer, requiring trimming.
Use brass fired in your gun and load only for the one gun. I label the boxes with the ID of the gun the reloaded brass came from, and date the reloads.
Keeping a notebook will save relearning lessons on what works and what doesn't.
I would suggest, seeing as the primer seating with most sets is done by driving the case out of the neck sizing die onto the primer with a rod and mallet, that you do wear hearing protection. It has been years since I popped a primer but it was a sharp crack that rang my ears. Cleaning the primer pockets does help, a cheap tool with one end for small and one end for large primer pocket cleanout.