LETS TAKE TIME FOR A SHORT DISCUSSION ON HEADSPACE AND HOW IT IS DERIVED

First, let me say that a small gap between the breech face and the end of the hood is desirable for reliable function. That this gap has anything to do with headspace is a common misconception. The headspace in a semiauto is the total room provided for the cartridge case, minus the length of the cartridge case.

Now I will explain what I said. The headspace is fixed in any 1911 by the distance between the top lugs on the barrel and the breech in relation to the end of the chamber that stops the cartridge case. If this is confusing, think of it this way.

The slide is machined with a fixed distance between the lug slots and the breech face. The barrel position is controlled by its lugs, and can only fit into this fixed space if the hood clears the breech face. The clearance should be enough to be sure of easy function even when severe fouling is present.

The depth of penetration of the cartridge into the barrel in relation to the lugs(chamber depth)controls the headspace because this is a fixed portion of the distance between the breech and the lugs. Headspace with any particular barrel/slide combination can be changed only by changing the chamber depth, or by replacing the barrel.

Headspace in a pistol is important for consistent ignition. Ignition depends on a firm consistent strike on the primer. Excessive headspace may allow the cartridge too far from the breech and may allow the primers to be blown out of the seats and affect ignition.