The VZ58 "gremlin" is a condition that can result in the striker not being caught by the sear and follwing the carrier home, leaving the rifle uncocked.
The "gremlin" shows itself when for one of several reasons, the sear re-connects to the disconnector after the carrier has disconnected them during its rearward travel.
The main reason, is that during the carrier assembly's rearward travel, the striker must push the sear back down in order to corss it. If the sear is pushed down as far as it gets pulled down by the trigger, it will pass the hook on the disconnector, allowing the disconnector hook to spring back up and re-connect with striker. The only reason this does not happen everytime, is that there is a small amount of overtravel, meaning that the trigger/disconnector travel slightly farther than the sear must in order to release sear. If the rifle were to have zero overtravel, a re-connect would occur everytime. What makes it occur when there is some overtravel, is that when the sear is pushed down it ihas inertia and travels farther than the striker actually forces it. In summary, if the sears inertia outweighs the overtravel + sear spring pressure a re-connect will be caused.
The other reason can be from the shooter. Many shooters, albeit unknown to them, will actually partially release and re-pull the trigger during recoil. This action would not be noticeable if it weren't for the fact that it can, in affected vz58 rifles, exascerbate the lack of overtravel and cause the "gremiln" to appear. This explains why some shooters experience the problem more frequently, even with different rifles than others.
When a re-connect occurs during rearward travel, it stays re-connected until the carrier hits the disconnector again on the way forward, the problem is that by that time, the striker has already crossed sear and is on its way to follwing carrier home, resulting in an uncocked rifle.
What is a "tabbed" carrier and how does it fix this problem?
A "tabbed" carrier, is an original bolt carrier, that has had a tab of steel welded to it, extending the disconnector lump forward. It fixes the problem completely by extending the lump forward far enough, that during the carrier's forward travel, it will hit the disconnector before the striker crosses the sear, so even if a re-connect happens another disconnect will happen before it is too late, and the sear will be at home to catch the striker and #### the rifle.
Why don't the Czechs have this problem on the original rifles?
The original rifles have an autosear, which holds the striker rearward until the carrier finishes it's forward travel. Therefore the striker cannot follow carrier home, and by the time the autosear has released the carrier will have already disconnected the trigger from the sear allowing the sear to return to its original postion and catch the striker.
