If you are talking about notching FMJ amo, I guess it would be a local law you'd have to check in to. As far as I'm aware, there are no Federal fingerprints in this area. Years ago, my uncles used to do it regularily.
The bullets, so modified, expand really fast, or theirs did. Shallow penetration was what they were getting.
SAFTEY ISSUE
I remember reading of a chap that ground the points off of FMJ bulets for 303BR. The result, was when fired, the core went out the barrel, leaving the jacket behind. Second shot, boom.
Most FMJ 303Br amo I have seen has no coverage of the lead at the bullet base.