basic dimensions for npt american national taper pipe threads
National pipe thread The taper rate for all NPT threads is 1 inch of diameter in 16 inches of length (3⁄4 inch per foot or 62.5 millimeters per meter) measured by the change of diameter (of the pipe thread) over distance of thread. The angle between the taper and the center axis of the pipe is tan−1(​1⁄32) = 1.7899° = 1° 47′ 24″.
Sawed-off shotgun A sawed-off shotgun (US, CAN) also called a sawn-off shotgun (UK, IRL, AU, NZ) and a short-barreled shotgun (SBS) (U.S. legislative terminology), is a type of shotgun with a shorter gun barrel—typically under 18 inches—and often a shortened or absent stock. Despite the colloquial term, barrels do not, strictly speaking, have to be shortened with a saw. Barrels can be manufactured at shorter lengths as an alternative to traditional, longer barrels. This makes them easier to transport due to their smaller profile and lighter weight. The design also makes the weapon easy to maneuver in cramped spaces, a feature sought by military close quarters combat units, law enforcement SWAT team users, and home defense purposes. With modern pump action/magazine tube shotguns, the shorter barrel limits the magazine capacity of the weapon due to the magazine tube protruding beyond the barrel. Therefore, the magazine tubes are matched in length to the barrel, which causes a reduction in the number of shells that can be held in the magazine tube.