The 30-30 head spaces on the rim so you can shorten the neck if necessary and have no affect on an 'pressure'. If you are worried about seating depth, that to should not be a problem if you stay in safe ranges with your charges. When I was shooting the 45-70 I noticed the cases which I retrieved from the factory Flex tip ammo were much shorter than the normal brass I use.
An armed society is not always a polite society, but it is a free and safe society!
Self Defense is an absolute and natural right!
Keep your head down and your powder dry!