The result can be seen in the attachment below
EDIT: After reading your posts, I started to realize that the efficienty or power or whatever of it wouldn't be that great. But I had alot of doubts about it from the very start anyway. Also I hesitated about the slide being way too heavy to act as a decent hammer. I'm going to re-design it and make a real blowback of it (air pushing the slide back this time) and perhaps including the tank in the magazine.
But to tell the truth it really doesn't seem too complex to me, I kept in mind that I only have limited/simple parts available and this is what should be possible with limited/simple parts.
*Redesigning*
Coming up: A real blowback without all the excessive things and maximum efficienty...









