Precision rifle, level pump, manufacturer unknown

[AirSupply]

I fired it. If I fire it with nothing it doesn't sound like much of anything happened. I put a 22 cal pellet in and shot it into a trap at close range. There are no sights on the gun. I tried to buy a scope mount and scope at a local gun store. Unfortunately that morning the 3 letter organization showed up and shut them down for a few days UN-announced. I'll go back over there soon and see if I can find a scope mount for it and see how it does.

The fact that it felt like nothing much happened makes it likely to be a giss system.
The 2 piston’s in sync cancel out the recoil.
Perhaps worth mentioning “Giss” in your topic heading. You might attract the attention of someone who knows more about your gun.

 

[JohnL57]

Try using a magnet on the compression tube-you can wrap a piece of paper on the magnet so it won't scratch the finish. If it's magnetic that tells you the material is steel. Many stainless steels are not magnetic. the scope or sight mounting block is one I've not seen before. Perhaps you might take a close-up view from the top and the side-inquiring minds wish to know!