Abstract: The bolt of a blowback operated weapon is driven rearward by multiplying the area acted upon by pressurized gas generated by a subcaliber bulleted cartridge or a blank cartridge fired in a subcaliber barrel inserted into the weapon barrel and attached to the weapon barrel muzzle.

Abstract: A barrel positioning spring moves a barrel in a blow-back operating pistol earwardly when the slide recoils in order to position the chamber on the barrel to receive a further cartridge with the return of the slide. This spring in a Colt(.TM.) .45 caliber pistol may be seated on the recoil spring guide rod present beneath the barrel. A removable loading ramp extension is fitted to the frame in the space between the chamber end and the next cartridge to receive such cartridge as it is being chambered by the returning slide.

Abstract: An interbar assembly (34) for reversibly attaching a supplemental device, e.g., grenade launcher (32), to a host weapon, e.g., rifle (10). A preferred interbar assembly attaches at its forward end to the bayonet lug (54) of rifle (10), and at its rearward end to the magazine well (31) of rifle (10). In a preferred embodiment, such connection can be made without the need for special tools and without altering the rifle in any way prior to making the connection. The invention also includes a supplemental sling strap attachment point (100), so the sling strap (29) can be readily relocated after attaching the grenade launcher (32), for example, to the rifle (10). Another aspect of the invention is a grenade launcher (for example) sight (104) mounted directly on the interbar assembly (34) that carries the grenade launcher (32).

Abstract: A semiautomatic pistol adapted to repetitively fire blank ammunition includes a frame, a barrel slidably mounted to the frame, a slide slidably mounted to the frame and adapted for reciprocal longitudinal movement relative to the frame between a forward battery position and a rearward position and an occlusion member at least partially positioned within a longitudinal bore defined in the barrel for generating sufficient back pressure in the barrel to move the slide rearwardly to the rearward position thereof. The occlusion member defines a length ranging from about 15% to about 60% the length of the barrel.

Abstract: An adapter device for a breech-loading firearm employs a cartridge carrier which holds a cartridge by its rim. The cartridge carrier holds the cartridge such that its rear face contacts a forward face of the cartridge carrier. The adapter device further comprises an adapter barrel, sized to be received within the barrel of the firearm (primary barrel), and spacer rings for supporting the adapter barrel within the primary barrel. The adapter barrel has an adapter breech for abutting a forward end of the cartridge carrier so that the cartridge extends into the adapter barrel.

Abstract: A rifle has a conventional gun stock, a receiver mounted thereon immediately rearwardly of an elongated barrel. The receiver has a forward end and a hollow forward end portion to detachably receive the rearward end of the barrel. The barrel has a rearward end portion that is tapered and which is complementary in shape to the tapered interior wall of the hollow forward end portion of the receiver. The receiver and the barrel have matching indicia marks to permit them to be properly aligned when assembled. The rearward end portion of the barrel has a pair of concave shaped wells which are substantially aligned, but partially offset, from threaded apertures in the receiver. Screws having rounded inner ends are mounted within the threaded apertures and penetrate into the wells and forcibly draw the barrel and the receiver into tight engagement with each other.

Abstract: A rifle construction with a swing-type barrel assembly is adapted for firing both conventional cartridges and non-conventional cartridges with a longitudinally extending barrel assembly having a first barrel and a second barrel mounted in opposed relation. A breech block interposed between the barrels is adapted for sliding cooperative movement with the first or second barrels in order to expel desired cartridges depending on the mode of operation. A housing is adapted to receive the barrel assembly in first and second firing positions.

Abstract: An automatic pistol adapted to repetitively fire blank ammunition includes a frame, a barrel unit supported by the frame and a slide unit reciprocally mounted on the frame between the forward and rear position. The barrel unit and/or frame incorporate structure which enables the pistol to operate in a highly reliable, repetitive manner without visible alteration to the pistol. A method for forming a blank firing pistol is also disclosed.

Abstract: A tubular insert for a shotgun such as an over/under shotgun provides a chamber end portion with a smooth outer surface. In order to achieve a good fit between the tubular insert at the chamber end portion and the shotgun barrel at its breech, a polymeric disk member is mounted in a correspondingly sized and shaped socket milled into outer surface of the chamber end portion of the tubular insert. The polymeric disk member extends a distance away from the outer surface of the chamber end portion to create a slight interference fit between the shotgun barrel bore at the breech and the tubular insert at its chamber end portion.

Abstract: An automatic pistol adapted to repetitively fire blank ammunition includes a frame, a barrel unit supported by the frame and a slide unit reciprocally mounted on the frame between the forward and rear position. The barrel unit and/or frame incorporate structure which enables the pistol to operate in a highly reliable, repetitive manner without visible alteration to the pistol. A method for forming a blank firing pistol is also disclosed.

Abstract: An augmented service pistol weapons system and ammunition has an extended barrel and an adapter sleeve and mount which supports the barrel and partially surrounds a forward end of the service pistol. Two hinged flaps have inward extending clamps which engage an inside of the front of a trigger guard on the pistol. A turn-to-release locking pin holds the two flaps together as the flaps are closed on the trigger guard. An arm rest extends laterally rearwardly along sides of the pistol and terminates in a curved rearward extension to support the augmented service pistol on an arm of the user. A fifty round magazine replaces the standard pistol handle magazine. Scopes and aiming devices are mounted above the extended barrel. A foregrip is removable and positionable at opposite lateral sides of the extended barrel and below the barrel. A variable power function assembly surrounds the barrel and allows selected release of gas to slow projectiles. A shredding device near the muzzle shreds bands on the projectile.

Abstract: A Mortar adapter intended to be received in the barrel of a mortar. The adapter includes a projectile firing tube and a breech region (2), wherein the projectile firing tube is intended to accommodate a practice projectile of smaller caliber than the caliber of the mortar barrel. The projectile is brought to a firing and locked state automatically as the projectile is inserted into the mortar adapter. There is provided a safety facility, which includes a breech block (7, 9) which is intended to be inserted into the adapter through the agency of a guide means (4, 5) which extends transversely to the longitudinal axis of the cylindrical breech (2) and when fully inserted forms the bottom of the breech.

Abstract: A shotgun barrel tube which has an enlarged chamber portion and an elongated barrel. A series of threads or grooves are formed circumferentially around the outer surface of the barrel tube to remove sufficient material to lighten the weight of the barrel tube and maintain sufficient strength to withstand internal pressure when a shotgun shell is discharged.

Abstract: The inbore sub-caliber device has spaced apart front and rear adapter plate members, each of which has an opening formed therethrough. A plurality of spaced apart rods extend between the front and rear adapter plate members to locate the openings in the front and rear adapter plate members in alignment. Support structure is coupled to the rear adapter plate. A gun comprising an elongated barrel and a rear receiver member is secured to the support structure. The barrel is supported in alignment with the openings in the front and rear plate members with at least a portion of the receiver located rearward of the rear plate member and the front end of the barrel located forward of the rear plate member to allow a bullet when fired to pass from the front end of the barrel by way of the opening of the front plate member.

Abstract: A practice tear gas round comprises a projectile having the same caliber as the standard tear gas gun, and a main adapter which is separately loadable into the launcher and has an outside diameter of the same caliber as the launcher while providing a chamber of reduced diameter for use of the launcher with devices of smaller caliber than the launcher. Preferably, an auxiliary adapter is receivable within the chamber of the main adapter in order to further reduce the caliber of propelling charge which is to be used for the practice round, while allowing removal of the auxiliary adaptor in order to receive in the main adaptor a standard 12 gauge shot shell, for example, for use of the launcher as a single shot 12 gauge shot gun. Additionally, the standard gas gun can be converted to a single shot rifle or shot gun for firing various other smaller calibers of cartridges and/or shot shells according to the auxiliary adaptor selected and inserted into the main adaptor for reception of a cartridge or shot shell.

Abstract: A small, extremely light weight kit containing components which, when wholly assembled, are a fully functional rifle, easily assembled in five minutes or less, and stowable in kit form with among other survival items, up to fifty rounds of small caliber ammunition, which is highly portable and useful.

Abstract: A system for changing the barrel of a firearm includes a firearm that has a stock having a trigger mounted thereon and a housing part removably attached to the stock in a fixed operative position. The housing part has a sighting mechanism on its upper side. A barrel is mounted in the housing part and a breech block is disposed in the housing part, which travels rearward on firing and cooperates with a locking system mounted in the housing part. A closing spring surrounds the barrel and means are provided for connecting the closing spring to the breech block. A firing pin is reciprocally received within the breech block. Also provided is means for removably retaining the barrel, closing spring, breech block, connecting means, and locking system within the housing part. A releasable key means, which holds the housing part in the fixed operative position, has a release position to remove the housing part in a direction substantially transverse thereto.

Abstract: A modular system for hunting rifles comprises barrels (13) of different caliber which can be attached via a barrel-mounted positioning rail (19) to a respective mounting tongue (11) of a stock which represents the basic unit. The stock can be constructed as long or short repeating rifle or as single-shot rifle so that any combinations of calibers and weapon types can be assembled. At its end, the barrel has a locking bush with locking lugs which cooperate with complementary locking lugs of an exchangeable bolt head (47). A longitudinal guidance system for the breech may be accommodated outside the breech area below the barrel, especially between positioning rail (19) and mounting tongue (11) to thereby attain a short overall length of the weapon. Also, through providing the locking bush with a downwardly directed cutout (53) which allows the passage of the projectile nose of a cartridge, the overall length can be further reduced.

Abstract: Adapter for safely firing a shotgun cartridge in a shotgun of a gauge larger than said cartridge comprising a tubular member having internal dimensions of a size to accommodate and hold snugly a cartridge of the gauge desired to be shot and external dimensions of a size to be accommodated in the shell chamber a shotgun in which it is desired to fire said cartridge.

Abstract: The shotshell size adapter fits into the breech of a shot gun, gas gun, grenade launcher or other gun and enables the gun to accept various sizes of shotshells and/or cartridges. The adapter includes a cylindrical mainbody which is inserted into the breech bore and a barrel which extends forwardly thereof into the gun barrel bore. The adapter barrel is releasably connected to the main body of the adapter by threads, preferably with rectangular, non-stripping lands and grooves, or by a turn wing and slot arrangement. Preferably, the front portion of the main body bore is recessed so that when the barrel is in place in the main body the bores of the main body and barrel abut each other and are concentric and of the same diameter. Alternatively, the barrel bore can be tapered to act as a shot choke. The rear end of the main body has an annular groove concentric with the main body bore and spaced outwardly therefrom to provide a finger space for lifting a shotshell or cartridge case from the main body bore.

Abstract: A multi-caliber firearm includes a breech, a pull-out claw at least partially disposed within the breech, and an adapter piece which is adjustably attached to the breech and onto which is formed a bearing surface which is located radially opposite the pull-out claw. The pull-out claw is capable of selectively engaging a cartridge case having a cartridge base. The position of the adapter piece is adjustable to enable the breech to accommodate cartridge cases having different cartridge base diameters. The adjustment of the adapter piece may be performed via rotation of an adapter piece formed with a plurality of steps ascending in a circumferential direction of the adapter piece, of via rotating an adapter piece which is screwed into the threaded bore and which moves radially with rotation of the adapter piece.

Abstract: A variable caliber self-loading pistol has a slide carried by a breech block slide of the gun with this slide projecting forwardly of the breech block slide so as to support the underside of a cartridge during initial rearward movement of the breech block slide as that cartridge is being extracted from the chamber. The slide also assists in preventing premature movement of a fresh round of ammunition upward from a magazine into the chamber.

Abstract: A detachable large-bore regular barrel of a shotgun is replaced by a light-weight, thin-walled, carrier barrel having a bore in which a smaller-bore tube and an adapter are mounted. This enables the shotgun to fire a smaller-gauge shotgun shell without changing the weight and balance of the gun, since the combined weight of the carrier barrel, tube and adapter matches that of the regular barrel and those parts are designed to provide the same balance. The carrier barrel is provided with the same kind of shell ejector/extractor as the regular barrel. The adapter comprises a tubular member which defines a firing chamber for the smaller-gauge shotgun shell and is disposed in the breech end of the carrier barrel bore, being threadedly connected to the tube therein. The tubular member of the adapter prevents inadvertent insertion of a larger gauge shotgun shell into the carrier barrel and thus provides a safety feature.

Abstract: The plug for shotgun or rifle barrel using black powder is outstanding in that it has a means (2) likely to extract the primer (a) destined to ignite the black powder contained in a chamber (c) of the said plug (1), when the arm is being opened.

Abstract: A shotgun having interchangeable barrels includes a barrel support member attached to a standard shotgun action. A plurality of barrels having substantially equal weights are sized and constructed to fit within and attach to the support member in operation relation to the shotgun action.

Abstract: This relates to an inexpensive conversion kit for handguns wherein inexpensive small caliber shells may be fired from a large caliber handgun. The kit includes a special adapter shell which is formed of two separable housing members into which there is inserted a small caliber shell, for example a .22 caliber shell. This shell will generally be of the rim firing type, whereas the larger caliber shell of the handgun is normally of the center firing type. Accordingly, the adapter shell will also include a special rim firing, firing pin which will be activated by the conventional firing pin of the handgun. The kit further includes a special barrel which is readily mounted in the handgun as a replacement barrel and which has a breech for receiving only the adapter shell. The converted handgun will operate in the normal manner.

Abstract: A breech load pistol and conversion kit which may be adapted to the frame of a semi-automatic pistol, such as a Government 0.45 pistol. The present invention may provide a modified slide which is slidably mounted to the pistol frame and is adapted to include a pivotable barrel assembly mounted thereto. The barrel preferably is suitable for target pistol accuracy. The barrel assembly may be pivoted exposing the breech end for single shot loading for target shooting applications. The conventional semi-automatic pistol magazine or clip may be replaced with a modified clip acting as a breech release actuator having a lever mechanism which is operable to release a latch holding the barrel assembly in engagement with the slide. The present invention also provides a pistol with a gas relief port. The present invention further provides a rim ejector for ejecting spent cartridges using a camming action occurring during pivoting of the barrel assembly to a loading position.

Abstract: A conversion unit for a firearm including a barrel assembly which replaces a standard shotgun barrel used on the type of shotguns that utilize quick change barrels which enables an existing shotgun to be converted into a muzzle loading rifle. The conversion is accomplished without affecting normal operation of the shotgun thereby enabling the muzzle loading conversion unit of this invention to be removed and replaced by the previously removed shotgun barrel. The muzzle loading conversion unit includes a barrel that has the same general outside dimensions as the standard replacement shotgun barrel with the conversion barrel including rifling and adjustable sights with the breech end being provided with a plug that is chambered to accept a standard shotshell primer with the breech plug also having a spring loaded extractor which will extract the spent shotshell primer a short distance.

Abstract: A sub-caliber automatic pistol of the double-action breech block type incorporates a frame having barrel-mounting ribs, a handle, a barrel-receiving slide with integral breech block, a firing mechanism of a larger caliber pistol, and a magazine adapted for storing a plurality of sub-caliber cartridges. The pistol includes an interchangeable barrel terminating rearwardly in a downwardly descending lug having an integral feed ramp defining a cartridge path for the larger caliber cartridges. A feed spacer is affixed to the barrel lug for defining a sub-caliber cartridge path which is elevated with respect to the first cartridge path.

Abstract: For a handgun, interchangeable barrel and shroud combinations including a short barrel and shroud adapted to be interchanged with a longer barrel and shroud in which the longer shroud has integral therewith, a rearwardly extending elongated arm for supporting from the rear end thereof, a rear sight. The rear sight may be adjustable for elevation only or for elevation and windage.

Abstract: A small arms caliber reducing adaptor kit including a barrel liner and cartridge insert sized to be inserted into an original small arms barrel and an original cartridge chamber respectively, the barrel liner and cartridge insert having corresponding reduced bores with the bore of the cartridge insert having a nose opening for a pellet and a base opening for a primer - the kit further including a primer seating tool.

Abstract: The present invention is a method and apparatus for reconfiguring an automatic rifle (10) for quick attachment and detachment of a grenade launcher (32). The apparatus invention comprises an upper rack (42) securable to the barrel (16) of the rifle (10), and a lower rack (34) to which the grenade launcher (32) can be secured. The upper and lower racks (42, 34) carry quick connect/disconnect fittings (66, 68, 78, 80) for mating and unmating of the launcher (32) with regard to the rifle (10).

Abstract: A firearm including a barrel holder for accommodating interchangeable barrels. A breechblock housing, connected to a stock, includes in a forward zone thereof, a recess having an abutment surface for absorbing recoil forces, with the barrel including a tubular member fixedly connected to a rear end thereof and including an extension fitting into the recess. The tubular member has a relatively large axial length and extends forwardly from a locking mechanism beyond a cartridge chamber of the firearm. The extension is provided at the rear end of the tubular member, and the abutment surface has an undercut portion partially extending over the extension from above. A downwardly projecting second extension is provided at the front end of the tubular member, with the second extension including a locking bolt recess. The breechblock housing extends up to a zone of the second extension and carries, at that location, a locked bolt cooperating with the locked bolt recess.

Abstract: An interchangeable barrel for Colt self-loading pistols is mounted on a mounting rail, which is fixed to the frame and extends along the longitudinal orientation of the pistol. In the longitudinal middle region of the mounting rail, a longitudinally oriented recess of circular arcuate undercut cross-section enters into said mounting rail and receives a clamping member (48) which is connected to the underside of the barrel (12) and adapted to the cross-section of the recess. The clamping member (48) is detachably and vertically adjustably connected to the barrel (12) so that the barrel can be clamped to the mounting rail by means of the clamping member.

Abstract: A liner for the firing chamber of a gun, designed to prevent ammunition "cook-off". The liner minimizes flow of heat into the chamber wall, incident to the combustion process. The liner also retards the flow of heat in the reverse direction, i.e. from the chamber wall into a chambered round. Liner design is such that the liner can be removed and replaced by a new liner when it is damaged.

Abstract: An improvement alignment device in an automatic weapon comprises a boss on the weapon barrel and an aligned entry slot, crossover slot and retention slot in the barrel support.

Abstract: For firing bullets or cartridges of different lengths but the same caliber, there is provided a barrel which is threaded at both ends and reversible, with different-length bores in each end. There is desirably also a protective cap for the threads at the distal end of the firearm, and also, at each end of the barrel, a lug or projection with opening therein to aid in securing the reversible barrel onto the part of the firearm proximal to the user.

Abstract: A gun barrel having a rifled-bore section at the breech end thereof and a smooth-bore section at the muzzle end thereof, the sections having a gas tight connection therebetween, the rifled-bore section comprising a first generally tubular body having a longitudinal bore and at least one spiral groove formed in the wall of the bore to a depth of a predetermined dimension, the rifled-bore section having a length corresponding substantially to the peak pressure point for the gun barrel, the smooth-bore section comprising a second generally tubular body having a longitudinal bore coaxial with the longitudinal bore of the rifled-bore section, and the longitudinal bore of the smooth-bore section having a diameter greater than the diameter of the bore of the rifled-bore section and less than the diameter of the spiral rifling groove.

Abstract: A revolver has a lowered firing line by alignment of the barrel with the lowermost chamber of the cylinder. The latter is swingably mounted on a frame at a location above the cylinder and cooperates with a firing mechanism in a compartment of the stock above the grip.

Abstract: A firearm is disclosed which includes a gun body having a firing mechanism and a barrel mount movable between a barrel loading position and a firing position. The firing mechanism is maintained in inoperative condition unless the barrel mount is correctly positioned in the firing position. A shoulder stock is releasably mountable on the gun body to permit the firearm to be selectively usable in pistol or rifle form. A plurality of barrel parts are selectively mountable on the gun body and include a first barrel of a length capable of firing baton rounds and gas rounds and a first insert of a similar length adapted to be fitted from only the end adjacent to the barrel mount into the first barrel to provide a smaller caliber barrel. A second barrel of a shorter length than the first barrel is provided and is capable of firing flare rounds.

Abstract: A gun is provided which is capable of firing a variety of projectiles driven by a variety of propellants. The barrel may be readily disconnected from the stock of the gun. The breech is designed to receive a standard gauge shotgun shell. Inserts are also provided with the same general configuration of a standard gauge shotgun shell, and when placed into the breech, allow the gun to fire a variety of projectiles. Inserts are provided which allow the gun to fire both center fire and rim fire rounds through a bore in the insert. A rocket insert is also provided which contains a smooth bore and is capable of firing rockets. An inertial firing pin is provided, which operates in conjunction with a floating breech plate. The floating breech plate is used in the firing of compressed gas bottles. A dual action spring drive is provided which is used to provide the necessary force to drive the firing pin and which also absorbs a portion of the recoil.

Abstract: An insert for a weapon barrel for facilitating the firing of a small caliber ammunition comprises a tubular member having a bore defining a distinct caliber with one end having an exterior surface ending in a raised shoulder forming an abutment for a compensating bushing positioned on the exterior surface and abutting the shoulder. A sleeve is positioned on the exterior surface alongside and abutting against the bushing. This end of the insert carries a first locking mechanism for locking the sleeve radially in the barrel. This includes a tapered spreader sleeve which engages with a tapered exterior surface of the sleeve positioned on the insert adjacent the compensating bushing. The spreader sleeve is urged into bearing engagement with the tapered surface of the other sleeve by means of a knot threaded over the insert and advanced toward the spreader sleeve. A safety key is insertable through an opening in the sleeve and it engages in a longitudinal slot formed on the insert.

Abstract: A bullet perforating apparatus for perforating subsurface formations traversed by a borehole. The bullet perforating apparatus comprises a gun body with a plurality of bullet perforating gun assemblies. The individual gun assemblies further comprise a gun barrel, a cartridge tube with propellant, means for igniting propellant, a projectile, and a seal at the well bore end of the barrel. The barrel further comprises an outer member and a replaceable wear member securely retained within the outer member.

Abstract: Disclosed is an interchangeable barrel for small arms of the type having sliding breechblocks, comprising a housing with a guide surface inclined downwardly to the rear, for releasing the barrel during recoil. In order to mount the interchangeable barrel in the weapon without any play, the barrel has an adjustable spreading element which can be wedged against the declining guide surface of the weapon.

Abstract: A gun conversion assembly for application to the receiver of an automatic pistol having a handle containing a recess into which a magazine holding a series of rounds of ammunition is insertible, the conversion assembly including a barrel to be secured to the receiver, and a connector structure having a portion which is adapted to be located within the magazine recess in the receiver handle and which acts to secure the barrel rigidly to the receiver. The connector structure may extend downwardly through the recess to the bottom of the receiver handle and have elements at the lower end of the handle tightenable to progressively pull the receiver downwardly into tightly contacting engagement with the upper end of the receiver.

Abstract: A unit is disclosed for use in converting a blowback autoloading pistol, such as a U.S. caliber .45 model 1911, into a gas operated one with the unit being adapted for connection to the receiver of the blowback pistol after its barrel and slide are removed. The unit comprises a shroud, a barrel and a gas activated piston for operating the bolt and its lock. The hammer, constituting part of the firing mechanism carried by the receiver, cooperates with the firing pin of the conversion unit in the same way as it did with the firing pin of the autoloading pistol. Instead of being used to effect a conversion, the structure involved in the conversion unit can also be used in making a completely new gas operated pistol or other firearm.

Abstract: A device is provided which enables a person to capture a fugitive without injuring the fugitive. The device comprises a tubular body having angularly disposed tubular barrels extending therefrom. The barrels each have a slot extending along the length thereof such that a pair of projectiles can be loaded into the device while a flexible line interconnects the pair of projectiles.To catch the fugitive, the device is aimed at the fugitive and the pair of projectiles are propelled from the barrels in diverging lines of flight. As the line extends between the diverging projectiles, the fugitive is engaged by the line. The momentum of the moving projectile causes the projectiles to wrap the line about the fugitive thereby entangling him and preventing him from further fleeing.

Abstract: A gun conversion assembly for application to the receiver of an automatic pistol having a handle containing a recess into which a magazine holding a series of rounds of ammunition is insertible, the conversion assembly including a barrel to be secured to the receiver, and a connector structure having a portion which is adapted to be located within the magazine recess in the receiver handle and which acts to secure the barrel rigidly to the receiver. The connector structure may extend downwardly through the recess to the bottom of the receiver handle and have elements at the lower end of the handle tightenable to progressively pull the receiver downwardly into tightly contacting engagement with the upper end of the receiver.

Abstract: An adaptor for attachment to the end of a rifle allows an individual to f from the rifle a different projectile than originally designed for the rifle, without substantial degredation in overall accuracy and throw distance of the rifle. The adaptor has a rifled cylinder which in the typical application will have progressive twist rifling. The tangential force acting upon the projectile within the progressive twist rifling area has a semi-elliptical shape and an exit value of approximately zero. An adaptor ring and outer shell are preferably employed to mount the rifled cylinder to the rifle and for aligning the adaptor axis and rifling with the rifle barrel axis and rifling.

Abstract: A conversion kit for allowing an M16 rifle to fire .22 caliber ball and bk ammunition in semi-automatic and automatic firing modes, comprises a bolt replacement which replaces the standard bolt in the rifle. The bolt replacement moves in the rifle receiver and is engageable with a sear trip bar of the conversion kit. The sear trip bar interacts with an automatic sear of the M16 rifle to permit automatic fire. A spring loaded detent is provided in the conversion for engaging a detent slot in the replacement bolt, to hold the bolt face against a chamber insert, to avoid bouncing of the bolt for automatic and burst firing modes. For the firing of blank cartridges, a shaft is provided in a chamber insert for reducing the diameter of the chamber insert to preclude the feeding of ball cartridges. An orifice in the shaft allows for escaping gases to leave the blank cartridge, but produces back pressure so that the replacement bolt can be cycled for blow back operation.