My slug gun for 10 years was a Moss 500 rifled 12 ga, red dot mounted to the top of receiver.
The 8 pound + trigger was like pulling a tooth, took it to a gun smith and he said moss shot gun triggers can not be "done", they are not like a "rifle" trigger.
Search high and low and never found ANY info on "doing" moss shot gun triggers.

Switched to Rem and had a 2.5# jewel trigger dropped in.

Rem 870, cant barrel, jewel trigger would be a good 100 yard gun.

Slack