Ordnance – Automatic – Movable barrel
Patent
1996-05-31
1998-03-31
Johnson, Stephen M.
Ordnance
Automatic
Movable barrel
F41A 504, F41A 526
Patent
active
057341206
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to self-loading firearms and more particularly to self-loading pistols of the short-recoil-operated type.
Self-loading pistols receive the energy to operate their loading mechanism from the energy of recoil. The recoil force drives the slidable superstructure of the pistol rearward on a horizontal platform built into a lower frame to extract the spent cartridge case from the firing chamber and eject it from the pistol. The superstructure is then returned to the forward or battery position by a return spring and is adapted to strip the succeeding round from a magazine and insert it into the firing chamber. Subsequent shots may require discrete trigger operations in the case of semi-automatic pistols or the trigger to remain continuously depressed in the case of automatic pistols.
The self-loading pistols referred to above include pistols and machine pistols in contrast to other types of pistols which do not self-load such as revolvers.
BACKGROUND ART
Self-loading pistols can be divided into a number of types such as pure blowback, delayed blowback, gas-operated, short-recoil-operated and long-recoil-operated.
With pure blowback pistols, the slidable superstructure consists only of a breech block slide. The slide is not locked to the barrel and the barrel is fixed to the frame. Immediately after firing, the recoil force starts to drive the slide rearwards thus commencing the extraction of the spent cartridge case. Thus, part of the extraction occurs during the high pressure period of the firing cycle. If the slide is too light, the case is extracted too soon and case rupture will result, leading to a failure of the loading cycle and possible injury to the user. As a result, the pure blowback type can only be used with low-powered cartridges since there is a practical limit to the mass of the slide. This type, however, is cheap to make and is quite common.
There are also a number of pure blowback pistols which use a gas retarding arrangement attached to the slide, eg, the Steyr GB and Heckler & Koch P7. The arrangement reduces the effect of residual gas pressure on the motion of the breech block slide and buffers the stop of the breech block slide.
Residual gas pressure is the gas pressure left in the barrel after the projectile has left the barrel. Residual gas pressure occurs due to the time it takes for the gas left in the barrel to leave via the muzzle. Although the residual gas pressure is low compared to the pressures when the projectile is moving in the barrel, it may persist for longer. The residual gas pressure can thus have a substantial influence on the recoil of the slide.
One such gas retarding arrangement consists of a piston attached to the slide and a cylinder attached to the frame. It should be noted that the stroke of the piston needs to be the same length as the travel of the slide. The cylinder is connected by a passage to the barrel bore. After firing, a small amount of propellant gas is bled into the cylinder. As the slide recoils, the piston attached compresses the bled propellant gas, thus producing a retarding force. It should be noted that the bullet has left the barrel by the time that this retarding process occurs, and so it should not be called a delayed blowback system as some do call it. A true delayed blowback process operates while the bullet is still in the barrel. As well, the initial case extraction still occurs during the high pressure period of the firing cycle.
With delayed blowback pistols, the slidable superstructure comprises a breech block slide but, as well, it has a delaying mechanism. The delaying mechanism is usually based on leverage in order to magnify the effective recoiling mass of the superstructure for a short period, thus reducing the extent of extraction of the spent cartridge case during the high pressure period of the firing cycle. This type can be used with more powerful cartridges but is quite expensive to make and is generally not cost competitive with the short-recoil-operated type.
With gas-operated pistol
REFERENCES:
patent: 2372542 (1945-03-01), Bloomquist
patent: 5060555 (1991-10-01), Sater et al.
patent: 5309815 (1994-05-01), Moller et al.
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