A foolishly ambitious project, spoiler alert, doesn't work the way I'd like it to.
It's a hop unit for airsoft Glock that shoots lasers instead of BBs. Basically like the "laser bullets" you get with real steel guns but for airsoft, with the blowback.
It takes the pressure which is usually meant for the BB to push a switch to close the circuit of a laser diode where the inner barrel is usually positioned.
Splits into two for assembly.
Testing the plunger / button:
Assembled, now tested in a gun with plenty of gas in gun.
Predictably, with the recoil shaking the gun around (This is on a steel slide Glock with Volante BBU), the target dot isn't very useful, it creates a streak instead of a clean dot, here you can see a test with a nearly empty mag, where the very last shot does not cycle the gun, here you can see a clean useful dot.
So that pretty much brings me to the end of this project as far as I'm prepared to go for now, oh well, was fun and learned a lot in the process.