This invention relates to means for enhancing the accuracy of a semi automatic pistol of the locked breech type without impairing, or otherwise hindering the functional reliablilty of the weapon. More particularly, this invention relates to means for more accurately engaging the rear portion of the barrel of a semi automatic pistol into the slide and preventing lateral and vertical movement therein.
The accuracy of locked breech type semi automatic pistols, such as the Colt Government Model 45 ACP, is dependant upon the ability of the barrel to be held in exactly the same position in the slide after each firing. In such firearms the frame, sometimes referred to as the receiver, remains stationary relative to the barrel and the slide. The barrel pivots downward and backward about a pivotal link connected to the frame for a limited distance upon the firing of a round. At the same time the slide moves backwardly along the frame, becoming disengaged from locking lugs in the barrel, and continuing its rearward movement sufficiently far to eject the spent cartridge and cock the firing mechnism before returning forward under spring pressure and loading a new cartridge into the firing chamber of the barrel.
Several factors contribute to the accuracy of such a firearm. Obviously the accuracy of the bore with its riflings is important as is the cartridge itself. However, these are parameters which are not affected by the fitting together of the parts within the pistol. There are critical fit dimensions which affect firearm accuracy. These all relate to the slide and barrel since the barrel is more intimately associated with the slide than the frame. Moreover the front and rear sights of the pistol are mounted in the slide and serve as the overall datum of accuracy of the pistol. It follows therefore that the fit of the barrel in the slide will, to a large extent, be determinitive of the accuracy of the pistol. More importantly, the reproducibility of the fit after each firing cycle is determinitive of the guns inherant accuracy potential.
There are several misconceptions regarding just what is required to assure accuracy in a semi automatic pistol of the locked breech type. The following axioms are offered as factors affecting the accuracy of such weapons.
1. the line of sight is the basic accuracy datum and not the frame, PA1 2. the barrel must point to the same place as the sights however the frame does not have to; PA1 3. lateral and vertical positioning of the rear of the barrel in the slide must be uniform from shot to shot; PA1 4. the barrel can be positioned no higher than the interior surface of the slide will allow; PA1 5. the muzzle of the barrel must be held concentrically in the slide from shot to shot; PA1 6. the under-barrel lug serves only to provide uniform longitudinal positioning of the barrel with reference to the slide stop pin as the weapon is presently constituted; PA1 7. the grip frame serves only to provide a handle, enclose the firing mechanism and provide a fixed location in space for the slide stop pin (the fit of the slide and frame rails is of no conseqeuence). PA1 8. the barrel link serves only to unlock the barrel from the slide.