US 4,057,003 A · Open bolt conversion apparatus

Abstract

An open-bolt firing conversion for the standard M16 rifle, which allows the rifle to be converted to open-bolt firing by replacement of parts and without otherwise altering the rifle. The open-bolt conversion is hammer-fired for reliability and preservation of the cyclic firing rate, and the conversion hammer straddles the conversion sear within the conventional M16 lower receiver. The open-bolt converted rifle can fire either semiautomatic or full-automatic under control of the conventional firing selector lever. The cyclic rate reducer is installed in a conventional M16 rifle, without further modification to the rifle, to lower the automatic fire cyclic rate to approximately 350 rounds per minute. The cyclic rate reducer includes an actuator assembly which is received behind a modified bolt carrier, and which is released to move forward and contact an automatic sear release only after the bolt carrier has completed at least a substantial portion of its forward movement. The actuator assembly includes provision for preventing the actuator assembly from bouncing rearwardly at the time of weapon recoil, before the gas-actuated rearward movement of the bolt carrier. The variable vector muzzle compensator receives the high-pressure gases at the muzzle of a firearm, and channels these gases to provide a force vector in a selected direction perpendicular to the line of fire. The direction of the gas force vector can be adjusted to accommodate a particular shooter, and the compensator is particularly effective to reduce muzzle climb in fully-automatic firearms. The multiple magazine apparatus includes a number of magazines bracketed together in a semi-permanent assembly, so that each loaded magazine is ready for insertion into a firearm as soon as the preceding magazine is emptied. Each individual magazine has provision for preventing the top round of the magazines not in the receiver housing from being dislodged when the firearm and the multiple magazine assembly recoil during firing. An auxiliary catch is provided to retain the magazines of the magazine assembly on the receiver of the firearm. The night sight apparatus is easily and removably attachable to a conventional M16 rifle without replacement or modification of the conventional sights, and provides a luminous sighting reference for shooting during low levels of ambient light.

Claims6

Dependent claims

Open bolt firing mechanism for a firearm of the type including a receiver housing having a reciprocating bolt mechanism and a hammer-operated firing pin carried by said bolt mechanism;

comprising:
sear means pivotally mounted within said receiver section;
said sear means having a bolt engaging surface to engage and retain said bolt mechanism in open position, and a second surface which engages said receiver housing in force transmitting alignment with said bolt engaging surface, so that forward force of said open bolt mechanism is transferred through said sear means to said receiver housing;
trigger means engagable with said sear means to pivotally move said sear means so that said bolt engaging surface is withdrawn from said bolt mechanism;
and
hammer means mounted for pivotal motion concentrically with and independently of pivotal motion of said sear means;
said hammer means having a pair of legs which extend alongside of said sear means, and a bridge portion which extends between said legs outwardly beyond said sear means, so that said hammer means can pivot without interference with said sear means to bring said bridge portion into firing contact with said firing pin when said bolt assembly has moved forward.

4 more elements

Apparatus for conversion to open-bolt firing of a firearm which is normally intended for closed-bolt firing and which has a receiver section, a reciprocating bolt mechanism within said receiver section, a hammer-operated firing pin carried by said bolt mechanism, and a firing selector having a recess selectably positionable for full-automatic firing to receive an automatic sear which is conventionally present in said firearm, or for semi-automaic firing, comprising:

sear means mounted within said receiver section and selectably operative to engage and retain said bolt mechanism in open position;
trigger means selectably engagable with said sear means to release said bolt mechanism for movement to a closed firing position;
hammer means disposed in said receiver section and selectably operative to strike said firing pin;
replacement automatic sear means which is substituted within said receiver section for said conventional automatic sear, and which is operative to retain said hammer in a cocked position and to release said cocked hammer in response to predetermined movement of said bolt mechanism,
said replacement automatic sear being disposed in nonoperative relation with said recess of said firing selector;
a trigger;
connector means which is operative in response to trigger pull to withdraw said sear means from bolt engagement for full-automatic firing of said firearm;
disconnector means selectably connected between said trigger and said connector means,
said disconnector means having a member which is located in relation to said firing selector to enter said recess when said trigger is pulled, provided that said firing selector is positioned for full-automatic firing;
and
said disconnector means being operative in response to engagement of said firing selector when in semi-automatic firing position to disconnect the operative connection between said connector means and said sear means, so that said sear means returns to bolt engaging position after firing a single round, irrespective of maintained trigger pull.

8 more elements

Dependencies are inferred from the claim text.

Open bolt conversion apparatus

Life of this patent

Open bolt conversion apparatus

Life of this patent

Abstract

Claims6