Comment on PM Mk16 SCAR-L by Hoborginc

Here is the picture.
The front of the trigger holds the hammer in place.
When the trigger is pulled, its front edge goes down, freeing the hammer's bottom "foot" and allowing the hammer to swing up. To make the hammer move, there would (realistically) be a spring (shown in purple) on the spring guide.
If you want the trigger to be spring-loaded as well (to return itself to the forward position), you would need a small spring (shown in red) just under its front edge. Making enough room for it may require making some holes, so it fits inside the hammer and receiver floor, instead of between them.

How does the hammer move back down? The bolt carrier would push it back down as it moves backward. Realistically this would be caused by the gas piston pushing it after a shot, but on the model this can be done by racking the charging handle. Make sure you reinforce the charging handle (putting extra glue on it, adding some layers of paper on the inside, or putting a different material inside it) and the area where it attaches to the bolt carrier if you intend to move it frequently).

However, I haven't tested if the hammer, returning to cocked position, would be capable of resetting the trigger as well. It should, but if it sticks in place, you will need to use a weaker spring for the trigger.

The disconnector doesn't matter on a model like this (glue it down if it gets in the way).