Early Style Group Industries .22LR Bolt
The early style Group Industries .22LR bolts are a two part bolt that in some ways resemble a 9mm closed bolt or possibly an IMI .22LR bolt for the semi auto UZI. The outer piece is a heavy steel bolt that does not move during firing. It does retract during cocking, pushing the inner bolt back, and is returned to the forward position by a return spring that is very similar to the recoil spring on a FA UZI. The inner bolt acts much like the carrier on a closed bolt UZI configuration. It has a moveable firing pin that moves forward as the bolt closes on the chamber. The return spring on the inner bolt is quite stiff and combined with the light weight of the inner bolt results in a rate of fire around 1500 RPM. The extractor appears to be the same as every other GI and Vector extractor. A connector bar is attached to the inner bolt and catches the sear when the inner bolt is retracted.
This design is very complicated, fragile, expensive to manufacture and not very reliable. This particular specimen shows evidence of hand fitting and might even be a factory prototype. The height of the sear tab on the connector rod is very critical. Too short and it runs away, too tall and it won't fire. The sear tab on this bolt had to be adjusted for every gun it has been used in.
Inside the inner bolt is a moveable firing pin and spring. It's cammed by a small rocker that pushes the firing pin forward just as the inner bolt closes on the chamber. The rocker mounts on the inner bolt and is cammed by hitting the back of the outer bolt. This timing is critical and can require adjustments for reliable operation.
The connector bar slides on tabs along its top and bottom. The bolt has slots milled into the side of it that the tabs slide in. The connector bar is inserted by lining up the front tab with the recess cut into the bolt. The second and third photos show the rearward and forward travel of the connector bar during firing. A lot of complicated machining with exact lengths and heights are required to make the connector work. Any misalignment causes excessive friction and can cause failures.
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Last Modified: September 27, 2003