As for powered flight, it depends what you need for performance. I had one off the wall idea a while ago for a very dangerous aircraft.
Assuming that experiments with gliders are somewhat successful, and enough is learned about airframes, perhaps a glider could be modified with a solid fuel rocket pack. It's lifted aloft by a large balloon, then cuts loose. As soon as it's clear of the balloon, the pilot ignites the rockets.
The rocket burns at a steady rate until gone--there's no throttleing back or landing early! I designed one using GURPS Vehicles aimed at 1880's level technology, but with sufficient knowlege to make an airframe that will fly.
If anyone's interested, I'll post it here.
Some will fly close to the heavens, but many will be blown there--I'd never wnat to fly such a beast!
Sub-machine guns--I seriously doubt it for some time. Someone could concieveably build one, but it would require such precision manufactureing that they would be horribly expensive, IMHO. Someone with a knowlege of machineing cuold make a far better estimate here.