Today i got back to the dovetail... it is no0w sitting so tight that no glue is needed... this also fits into my plan, that, once the blaster is finished, i should be able to remove all pieces without destroying anything, when i need to repair the electronics.
Unfortunately, i sew too deep at the dovetail, but meanwhile this can be repaired easily with green stuff :-).
Thanks again to Dracotrooper, he helped me a lot with his posted picture!
I decided to rearrange the magnets for the magazine, as the switch, which will be mounted soon, would not fit in with the old solution. Now it sits in between and works great.
When the magazine was clipped in, i recognized how far the progress of the blaster is, meanwhile :-) :-)