All my 30 carbines get fired in my Ruger Blackhawk, so I am looking for lowest cost bullets. But we are talking about a 30 carbine, not some exotic long distance rifle. I really don't think the difference in BC will make much difference to you.
But if you do decide to go that way, what is important is bullet seating depth, not OAL. So determine the seating depth (total bullet length - exposed bullet length after seating) and use the same seating depth for the spitzer nose bullet. That is what determines cartridge pressure.