In 1916 Albert Bacon Pratt of Lyndon, Vermont was issued patent No. 1183492
for a "gun adapted to be mounted on and fired from the head of the marksman." The wearer fired the gun by blowing into a tube. Most of Pratt's patent application is fairly dry and technical, but here he offers his thoughts on some of the advantages of his invention:
The weapon described has many advantages. The gun is automatically aimed unconsciously and incidentally to the turning of the head of the marksman in the direction of the target. In self-protection, one immediately, instinctively turns the head in the direction of attack to see the enemy, or, in hunting, toward any sound made by nearby game. Thus the gun is automatically directed toward the mark in the course of the first instinctive movement. With the gun thus aimed, the only further operation necessary to fire the same is to blow through the tube and thereby expand the bulb and operate the trigger. This is accomplished entirely from the head of the marksman, leaving his hands and feet free further to defend himself or for other purposes as desired. Under some circumstances the gun can be fired not only without the use of the hands and feet, but also without the use of the eyes of the marksman. For example, in hunting at night if an animal made a sound in underbrush, the head of the marksman would be instinctively turned in the direction of the sound and then the gun would be fired, without the use of the eyes of the marksman.
Pratt then points out that his invention is useful not only in combat, but also in the kitchen:
The crown section of the helmet when detached from the base of the helmet may be inverted and used as a cooking utensil, the elongated hood projecting therefrom for protecting the barrel of the gun serving as the handle therefor.
Pratt claimed he had solved the problem of recoil:
The "blow-back" causes the breech-bolt to retreat and automatically cock the hammer, but the strong spring back of the breech-bolt forces the same so quickly forward again following the recoil, that the two movements naturalize one another so promptly that no discomfort to the wearer results from the recoil.
But I suspect he didn't have all the bugs ironed out, which must be why such a useful invention never caught on.