If I find a lower receiver out of state at a fair price, can I purchase it as "other" vice "pistol" or "rifle" on my forms? Pistol sales are not legal out-of-state, rifle sales are, but what about "other?"

I travel a great deal, and frequent shops. If I find a great deal on a receiver, I'd like to pick it up without having to choose on the spot about whether I want to build it into a pistol or rifle.

Thanks,
-Seph