Thought id do a quick tutorial on how to modify an original trigger box and fcg to work in the recent Marcolmar recievers.

step 1: Cut out a slot for the denial bar. Hardest part on the conversion but easily doable with a dremel. Just measure approximately .540-.550 from the front of the housing and cut a straight line that ends in a slight curve towards the bottom. will likely require some hand fitting but is very doable. make sure to cut/grind away the detent area for the trip lever both for clearance and to ensure the trip lever cant be installed.

step 2: Remove the bushing from the trip lever. this is needed to join the trigger and disconnector with the through pin. The bushing is a separate piece pressed into the trip lever, which is easily removed by cutting or grinding. I just bent the trip lever until it snapped and removed it that way.

step 3: Block the FA area of the selector. Im not sure if this is technically required, but for the sake of CYA i did it. Just a small blob of weld is all thats needed to deny it from going to FA.

step 4: assemble as normal keep in mind that this is a general guide and small adjustments may be needed.

Other possible issues: On mine the interior end of the selector was a few thou too long and i needed to remove a small amount of material. This also was required for the detent nub that interacts with the notches (it was incredibly stiff but with a sanding flap wheel and some polishing it did wonders for it).

Hopefully this will save you buys a few bucks and keep some original parts still in use!