Like shortgrass posted, ITAR will more than likely be a gotcha. That and dealing with clueless gate agents and TSA personnel could turn in to a real "film at 11" incident. Brownell's ships target bullets internationally. I would check with them.
I just re-read your post. Are you taking live ammo or just projectiles? If ammo, you are limited to 5 kilos OF AMMO in some type of container that holds them where they can't rattle around loose, like an ammo box, no plastic bags. They must be in checked bags, no carry on. These are ICAO regs, so generally speaking, countries and airlines don't matter, it's five kilos not including the containers. In to Scotland? You're on your own there.