Military corrosive ammunition dating
Photo Aperture Sight - See Peep Sight APUN - Action Patent Use Number.Under patent law during the period of greatest creativity in the British firearms trade (circa 1860 - 1910) gunmakers typically numbered each patented component with its own number of use of the patent (not the number of the patent itself as registered with the patent office as in the USA)---irrespective of the serial number of the firearm.Photo Backboring - Enlarging the internal diameter of a shotgun barrel beyond its proper standard (.729" in 12 gauge) by reaming, in an effort to reduce the recoil or to improve the shot pattern.Backboring removes steel and therefore strength from the barrels---possibly making them unsafe.Back Action - A sidelock action where the mainspring is mounted rearward towards the butt.The back action is often used in double rifles where the need for strength requires as little steel as possible be removed from the bar of the action.
Backstrap - Rear, metal, part of a handgun---which together with the frontstrap, provides a mounting frame for the grips.Photo Ball Screw - See Worm Ball & Shot Gun - A firearm, built to be able to shoot either a single projectile or a load of shot pellets; generally built heavier than their shotgun counterparts and fitted with rudimentary rifle sights; often either with robust rifling just at the muzzle or with Lancaster Oval Boring.See Paradox Ballistics - The study of the action of propellant powders upon projectiles, their speeds, energies and trajectories.Photo Anson & Deeley Action - A type of boxlock action design for a break-open gun, patented in 1875, the essence of simplicity utilizing only two springs and three moving parts (per barrel).One of the most successful action designs ever, and still produced to this day by innumerable makers in many countries. any replica of any firearm described in subparagraph (A) if such replica (i) is not designed or redesigned for using rimfire or conventional centerfire fixed ammunition, or (ii) uses rimfire or conventional centerfire fixed ammunition which is no longer manufactured in the United States and which is not readily available in the ordinary channels of commercial trade.
Such a firearm will fire continuously as long as the trigger is held back, until the magazine is empty. A firearm thus activated, but which shoots only one bullet with each separate pull of the trigger, while often erroneously referred to as "automatic" is more properly termed Semi-Automatic.