A reference model of an M16 Fire Control Group. This CAD should be to-spec, as it was drawn from the M16 technical data package. This CAD can be used to test fitment in software without risking your doggo's lives. The parts in .step and .stl are precision located as if they are in a M16 lower. In the Inventor Source files, you can see this lower by enabling visibility on it. Each FCG part is good to the Colt specs I have. The disco is an A1, the Selector is A1, Sear is A1, Hammer is a combo of A1 and A2 dimensions (my drawing set is missing some of both A1 and A2). Trigger is combo of A2 and M4 specs. Same story as the hammer. In the step and stl folders, I have included the assembly at 5 key stages - fired in full auto, fired in semi auto, cocked in full auto, and cocked in semi auto both before and after trigger reset. The names of the files and renders should make it clear which is which. In the Inventor source files, you will find I've labeled the constraints for the various FCG positions. You can use these to get special snapshots of how the FCG components line up. Just check/uncheck the 'suppress' option when right-clicking the constraint you wish to enable/disable. The lower in the source files should be to spec, but I cannot verify that. The FCG pin holes are right and that's all I checked. besides that it's a standard AR lower with the shelf milled for FA parts. As usual, this is for education only or whatever. Don't do anything too fun/stupid. If you wanted to cast or print FCG parts, this would be a good place to start.