Sorry, wasn't too clear in my post. The gun used to come ported, but I believe it no longer does. It is now up to you to get it done.

(and to someone else. 450 Marlin is nothing more than a belted 45-70, made so that you could get the performance of a hotter load without the ammo companies worrying about someone's old sharps blowing up in their face. If you handload, there is nothing that the 450 does that the 45-70 can't. Just another excuse to make you buy a new set of dies)