Here is my latest creation made for the MS525L valve to pilot my new piston valve...
Showing the mechanism in the locked position
And once fired it looks like this...
From left to right - housing/sear/trigger, spring, firing pin/hammer, spacer, hose clamp, and soon to be piston valve
On the upper right hand corner you can see how the charging handle will interface with the hammer to push it back.
The trigger is made out of 8mm stainless steel rod, attached to the connecting piece with an M3 screw and nut. The connecting piece for the housing, sear and trigger is also 8mm stainless steel. Sear is a piece of M5 all thread with a couple of washers, firmly locked to the connecting piece with 2 nuts. Housing is most likely 6000 series aluminum. I drilled 2 holes through it for 2 M5 screws. The one on the left is the pivot point and the one on the right holds the spring.
I still need to give the trigger a round bend to go around the chamber where it connects to the T and sand/polish the whole thing.