Lands - The spiraling raised portion of a rifle barrels interior remaining after the grooves have been cut or formed.


Lead Crusher - A pure lead cylinder used in a pressure gun for obtaining lead units of pressure (L.U.P. or lup). Formerly used to test low-pressure cartridges such as shotshells, this system is now obsolete in the U.S.


Leade - See throat or freebore.


Leading - Lead deposited in the bore from the friction of lead bullets rubbing against the bore, or from gas-cutting of lead bullets. A form of metal fouling, some leading is normal; however, excessive leading can destroy accuracy and raise pressures.


Line of Departure - The straight line at which a bullet leaves the muzzle of a firearm, equivalent to the axis of the bore extended into space. The bullet immediately falls away from this imaginary line due to gravity.


Line of Sight (LOS) - The straight line through the sights of a gun to the point of aim.


Loading Block - A block of material, usually wood or plastic, with rows of holes to conveniently hold a number of cartridge cases during the loading operation. Especially useful when charging cases with a powder measure.


Loading Density - Ratio of the volume of powder charge to the volume of the case.


Lock Time - The period of time between the release of the sear by trigger movement and the instant the priming mixture detonates after being hit by the firing pin.


Locking Lugs - Protrusions on the bolt which engage a mating recess inside the receiver ring when the bolt is closed. This feature prevents the bolt from moving rearward when the rifle is fired. Usually used in reference to rotary bolt-action firearms.


Lubricant - Case sizing lubricant is used to reduce friction when sizing cartridge cases. Bullet lubricant is used to help minimize leading when firing lead alloy bullets.


Lubricator-Sizer - A tool used to simultaneously size and lubricate cast lead bullets. Often contracted to lubrisizer.