At the beginning of this project, the designer began by experimenting with possible selective-fire conversion systems starting from the original factory trigger components. Although the open-bolt conversion system, which is very simply done and requires no modification to the receiver or trigger housing, has proven to be the ideal selective-fire conversion for the 1022, coming to that conclusion was not so easy.
The first several conversion attempts proved very unsatisfactory. These conversions incorporated a "drop in" type auto sear that is positioned in front of the hammer pivot portion. The original hammer has only a single notch for trigger sear provision, so a second notch was cut just above the first for the auto sear engagement. The automatic firing system is similar to that used on the Belgian FAL or the Russian AK-47 assault rifles. A long groove was milled underneath the bolt about 1/8-inch wide and 1/8-inch deep. About 3/16 of an inch was left ungrooved at the bolt's rear end to act as a tripping shoulder for the auto sear. This tripping shoulder hooks the auto sear tail end (top part), which protrudes about 3/32 of an inch above the trigger housing frame, just before the bolt fully closes.
The above conversion utilized the basic trigger mechanism except for the original push-button-type safety. This safety has been replaced by a three-position safety and fire selector lever. The original disconnector system was activated by the hammer cocking action. The hammer has a small lug which secures the hammer spring rod in place and pushes down on the disconnector hump during cocking action so that the sear can rebound and catch the hammer as the bolt moves forward after a full rearward recoil. The hammer back lug and the disconnector hump are slightly reduced as is the back of the trigger to increase the trigger pull. This additional pull accomplishes bypassing the hammer back to prevent the disconnection of the sear. Once the disconnector system is bypassed, the auto sear will catch the hammer in the fully cocked position as it is being depressed by the recoiling bolt. On forward recoil, the bolt will hook the auto sear tail end at ful closure and release the hammer automatically.
The provision for selective-fire functioning in the above conversion was totally controlled by the selector lever notches. The shallow notch grooved for semiauto functioning allows enough contact for the hammer back lug to reach and depress the disconnector hump. This action disconnects and releases the semiauto sear (the original sear) to its normal position in order to catch the hammer as soon as the auto sear releases it after bolt closure.
In the full auto mode, the deep notch of the selector provides longer trigger pull. When the trigger is pulled, the disconnector hump will automatically override the disconnection of the semiauto sear. The disconnector hump will not be pressed down by the hammer's cocking action since it now rests a little forward due to the longer pull of the trigger and the hammer back lug that normally depresses the disconnector hump is no longer in line with it. Only the auto sear catches the hammer when the bolt recoils after a shot is fired. This results in automatic firing each time the bolt fully closes and the trigger pull is maintained.
The conversion described above could have been the simplest and most ideal conversion for the 1022 rifle. Amazingly enough, however, even though the theory is faultless and the action works perfectly when the system is operated by hand, when the weapon is fired, it will produce only semiautomatic functioning. When the selector is set at full auto, the weapon fires only the first chambered round leaving a very light firing pin impression on the second chambered round. The result is a single shot and an unfired shell in the chamber.
Several remedies were attempted to correct the problem but the weapon still would not operate properly in the automatic firing mode. Among the remedies incorporated to get the second round to fire were a stronger recoil spring, a longer firing pin, and a delayed hammer release. These additions made the weapon operate in a burst-fire mode firing three to five rounds before the action stopped due to an unfired shell in the chamber. Several top-of-the-line brands of high velocity ammunition were used in the test and still the results were the same. Various magazines and more honing on the operating components still did not make for reliable operation.
Perhaps the most important factor in the failure of the conversion described above utilizing the original factory trigger mechanism is the offset location of the recoil spring. The recoil spring was positioned to the left side of the bolt. Inside the receiver, there is enough gap to insert a dime. These two features tend to shift the bolt to the right, and on automatic firing, this shifting action combined with the slight bouncing of the bolt once it hits the chamber face will leave an open gap. Therefore, when the hammer is released and hits the firing pin, the impact is cushioned. When the rim of the cartridge is hit, the bolt is not fully closed against the chamber face. The hammer therefore delivers its full impact to the bolt instead of the firing pin which results in a misfire on the next round.
Perhaps the only remaining remedy would be to use a dual mounted recoil spring assembly to equalize the forward thrust of the bolt when it is closing. But since this would require extensive work on a milling machine and would therefore be costly to manufacture, the above-mentioned conversion procedure has been discarded in favor of the reliable open-bolt design. The open-bolt design system recommended here for converting the "Ruger 1022 to a superb selective-fire weapon has been extensively tested and has proved to be reliable in normal shooting once the conversion parts are properly fitted.
To convert the original closed-bolt, hammer-fired design of the 1022 rifle to an open-bolt system, a new trigger mechanism must be incorporated. In considering the conversion, the main priority became simplicity of manufacture and no modification of the receiver or the trigger housing. Able to meet these requirements is our super-compact trigger mechanism, which is assembled as one unit and which can be installed or removed in a matter of seconds after the gun is stripped. The selective-fire converter is a "drop in" type neatly assembled in one compact subgroup consisting of the sear and trigger assembly. Only one spring powers the two parts. The sear has a built-in tripper that engages or disconnects from the trigger depending on the mode of fire selected. A small rectangular-shaped sheet metal housing contains the entire trigger group in a single compact unit. This unit is easily hand formed using improvised dies. This arrangement allows the converter unit to be inserted as a pack inside the original trigger housing plate once all the trigger components have been removed except the magazine catch assembly. The converter unit is inserted inside the frame and is secured in place by the original trigger and ejector pin. After the unit is inserted in the trigger housing frame, the original ejector is then assembled in the usual manner while the ejector pin is being pushed in during final assembly.
Since the converter mechanism comes as one subgroup, no modification at all is required on either the trigger housing frame or the receiver. This leaves all the trigger mechanism usable should the operator want to switch back to the nonselective mode of fire. Simply substitute the appropriate components.
The one part that requires modification is the bolt. Since we have moved from a closed-bolt to an open-bolt design system, a new pivoting hammer bolt modification is necessary. Fixed firing pin systems are simply unreliable unless the firing pin is positioned on the feed rib itself so that it will not interfere with the loading process. The firing pin on the 1022 is top-mounted and is slightly offset to the right side.
Putting a fixed firing pin on the feeder will not permit the modified bolt to be used in the nonselective firing mode should the operator want to switch back from selective fire. Also the firing pin protrusion would be very small and wear faster than the original firing pin assembly utilizing the conventional pivoting hammer. A firing pin adapter has been incorporated so that the modified bolt can be used with the original factory trigger components for nonselective operation. The use of the firing pin adapter actually improves and strengthens the weak part of the firing pin: the rear end of the firing pin used on the gun is narrowly tapered and is subject to peening and bending after heavy use.
In the conversion process, this fragile tapered end of the firing pin is cut off and replaced by a 1/8-inch thick adapter that will outlast even the hammer itself with proper heat treatment. A long notch for the adapter assembly is cut at the rear end of the bolt. The easiest way to make this long notch without machining is to simply install three blades in your hacksaw. Grip the bolt in a padded vise with its rear end on top, being careful not to dent the bolt body. Then cut by following the straight line of the firing pin assembly groove on top of the bolt so you can make the cutting stroke straight. Cut the slot to the specified length, then smooth the rough hacksaw cut with the right size flat file until the 1/8-inch adapter can be inserted and moved freely inside the slot.
Another necessary bolt modification is the cutting of the step for sear engagement. This cut is made parallel to the bottom of the inclined surface on the bolt's underside. The inclined surface causes the bolt to undergo a slight retarding effect during rearward recoil after a shot is fired. This retardation gives time for the top cartridge in the magazine to position itself properly before being picked up by the bolt feed in the chambering process. The top center portion of the trigger housing frame has a mating step for this inclined surface on the bolt. The bolt is held on this step momentarily before being forced downward by the contour of the receiver's rear end until it is overcome by the recoil spring's resistance, thereby completing the cycle of operation. A step must be cut underneath the bolt so that the sear can engage it. The original, inclined surface will catch with the sear nose. However, it will not safely hold it in "open" position, and by simply pushing hard on the cocking handle, the bolt will be released and will fire the weapon accidentally. For this rejt son, a straight step is needed in order to lock the bolt positively with the sear in the open bolt position.
There are two ways of making this step. The method described in this book is preferred because the original trigger components can be used for nonselective firing. Note that the one photographed for the book has the underside of the bolt milled using a 1/8-inch diameter cutter. Note too that only the area which is in line with the sear nose was removed leaving the rest of the inclined surface untouched. The inclined surface of the bolt that is parallel to the mating step on top of the trigger housing frame (about 1/4-inch on both sides of bolt) must not be cut. If these areas were also cut, the bolt would engage fully with the trigger housing top step, and would not move forward. It would be locked permanently in place and would cause unnecessary shaving on the inclined part of the trigger housing plate when the bolt was forced forward.
The second, unpreferred method of making the straight step underneath the bolt is to cut the step using a flat or square mill file if a lathe is not available. This will, however, affect the entire inclined surface of the bolt as it is not possible to cut the step this way without cutting horizontally through the whole inclined surface. This will make the bottom part of the straight step in the inclined surface about 1/8-inch deep as required for sear nose engagement. This bolt should not be used with the original trigger mechanism for nonselective firing. The bolt should be used only on the selective fire mode with the "drop in" trigger group in place. Since the converter housing is level with the upper middle step where the lower part of the bolt travels, the bolt will not be retarded during recoil. It will instead operate in a straight cycle. The inclined surface step for the retarding effect can be cut on the converter housing frame and shaped to the top of the trigger housing frame, but it is functional only with the milled bolt step described in procedure number one.
Another way of making the step if you do not have a lathe is by using a 1/4-inch diameter counterbore. A good vise and a drill press will be needed for this method. The counterbore will be positioned exactly at the point where the sear nose is in line when the bolt is assembled. A 1/8-inch deep counterbore will be needed for sear nose clearance. To do this so that the bolt still retains the original inclined surface (for retarding effect) and is still usable with the original factory components, the sear nose that engages with the counterbore of the bolt must be rounded up to blend with the counterbore radius. The contact surfaces of both the sear and the bolt must be highly polished after final fitting to ensure smooth operation. This will also produce less friction and wear on contact areas.
The open bolt design system incorporated in this project is well designed and carefully put together as a result of the extensive testing of various prototypes. However, the rifle cannot be field stripped without the use of a screwdriver, so even a "drop in" sear is going to require a few extra seconds to remove or install without opening the rifle. For this purpose, we have incorporated the "quick-change" selector system. Changing the selector is the fastest way of making your gun fire in either the selective mode or nonselective mode without stripping the gun.
Using the open bolt system, you can make a quick changeover from selective to nonselective fire by simply using two selectors. Use a lever-type selector with three indexes and double notches for selective fire. If you wish, the original push-button safety may be used for nonselective fire. The original push-button safety, however, will need to have a small plate about 1/16-inch thick soldered on top of the deep notch where the sear makes contact. The original depth of the push-button safety is a bit too deep for the sear and if used as is will produce automatic fire only. Once the metal plate is soldered into the push-button safety notch, you can gradually adjust the depth by cutting small bits from it until the sear nose is level with the converter housing top wall. This will allow it to clear the bolt when trigger is pulled. Make sure, however, that the disconnection of the sear trip and trigger is still positive when the trigger is pulled to prevent doubling or automatic fire.
In the field stripping procedure, the lever-type safety selector mechanism must be replaced by the push-button-type safety in order to lift the receiver body from the stock. Better still, make a plain slave pin about the same diameter and length as the original push-button-type safety. Both ends of the slave pin must be chamfered for easy insertion when replacing selectors. Care must be taken during selector changes. The selector index plunger is under spring tension. Support the other end of the pin that is being pushed out by the selector pin being inserted so that the ends of the two pins abut one another when passing the spring loaded plunger. Failure to do so may cause the plunger to disengage
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