Be careful. Sometimes there is no copper base on those rounds. By filing you will create a gilding metal tube around a lead core. Bore damage, jacket slipping and pressure issues can arise. I saw a .303 British lee enfield badly damaged by a home made hunting round made from a ball military round. I would pull a bullet and if the whole base is encapsulated with jacket you should be OK. Some expansion tests on some wet phone books would be a good idea also.
just my two cents, I get bored too....
Darryl