Air Gun Home :: View topic - Hatsan AT-44 Hammer Bounce Preventer

rsterne · Moderator

Were you aware that the Hatsan AT-44 has a factory built-in hammer bounce preventer?.... I wasn't until today when I decided to figure out what the weird little wishbone shaped part between the breech and the main tube does.... Unlike the common HDDs that rely on friction, this clever little part provides a positive latch to stop the hammer from rebounding after it has struck the valve, and hence makes it impossible for enough energy to be stored in the hammer spring to throw the hammer back against the valve stem, possibly re-opening it and wasting air.... I don't know if there are any other PCPs with a similar device or not, but I really like the fact that this device doesn't rely on friction and hence won't introduce any variability into the hammer cycle.... Here are detailed photos of it, and a description of how it works....

The hammer in the photo above is resting against the valve stem, ie it is in the position it would be in after a shot.... You can see the little lever, and just behind the hammer is a notch which would prevent the hammer from moving back past it and compressing the hammer spring, should it be driven backwards by the closing of the valve.... There is normally a small spring in the hole, I had to remove it to take the photo.... Note the bump immediately above the rivet that holds the assembly together.... It plays a vital part in the functioning of this device.... Here is a photo of the lever sitting in the recess in the breech, also in the firing position....

The large nut on the right end of the lever is simply a weight taking place of the spring so that I could take this photo.... The end of the closed bolt is just about directly under the pivot pin for the lever, ie ahead of the bump where the rivet is.... When you first open the action, drawing back the bolt, before any cocking of the hammer occurs, the end of the bolt hits that bump, compressing the small spring and tilting the lever so that the hammer can draw back to cock the gun, like this (action shown closed in this photo)....

The notch is lifted up away from the hammer (depressed into the breech in this photo), allowing the hammer to clear it as it travels back to the cocked position.... When the action is closed, the lever returns to the "firing" position as in the middle photo.... When the gun is fired, the hammer passes the notch in the lever, momentarily lifting it upwards, compressing the spring as it passes.... During the time the valve is open, the spring returns the lever to the "firing / fired" position, and the hammer can no longer travel back more than a fraction of an inch.... Virtualy no energy is stored in the hammer spring, so the hammer can't open the valve a second time....

This is a clever bit of engineering, and I congratulate Hatsan for incorporating this simple but effective device into the AT-44.... I dont know if the BT-65 has the same thing or not....

Bob

radar · Silver Status Member

I like that.

Also its good to see there is life on this forum. Been pretty dead lately.

robert w · Senior Member

i noticed that its sorta dead lately and i thought you killed them radar haha