Milspec is a word often misused and abused, sometimes people use it to cover a lot of areas when they do not have specifics.  When it comes to the AR system, this pretty much means TDP.  Sometimes it's not feasible, and impossible to produce civilian products using military specs.  Receivers may adhere to many milspecs, but not all of them.  Selector is another one.

Since we spent a great deal of time on the development and refinement of our selectors, I can chime in on the selectors.

The military spec selectors are decidedly NOT the same as any semi auto version, aside from the obvious select fire vs. semi only aspect.

Milspec M16 selector's detent groove goes 360 degrees, even to where there is no detent hole.  We can only think this was meant for a 4 way fire control group, it serves no other purpose otherwise.  
Semi auto selector's detent groove goes 90 degrees.

Milspec M16 selector's detent holes are bi-directional, in that you can rotate past the selector either way when the detent is engaged.  On many receivers, there are selector stops on the left side of the receiver to prevent over-rotation, but on M16 receivers without selector stops, or if you put the selector lever on the right side where there are no selector stops, (such as ours, which is fully modular), an M16 selector will rotate 360 degrees.
Semi auto selector's detent holes will only allow you to rotate it between the detent holes, not beyond them.

Thus all semi auto selectors are not "milspec", they cannot be.  

There are no standard to speak of when it comes to specs for the semi auto detent hole, detent groove depth, shoulder depth, and groove angles.  There's also no written in stone specs we know of regarding the selector's bar / axis / center length.  Given that all receivers vary somewhat in width, this often becomes a problem.  A very thick receiver will find the selector lever binding on it, a very thin receiver will see pronounced gap between the receiver and levers.  We have spent countless hours and much of our resources to find a great combination, honestly nobody thought there was so much to a simple selector.

Pics:
From left to right: Battle Arms Dev. semi auto, cast, unknown brand M16 selector, and Battle Arms Dev. M16 (all Battle Arms selectors are CNC machined)


Special attention to the M16 selector detent holes and groove.  A milspec selector's detent holes will allow you to rotate it both ways.  On our current M16 selectors, this can't be done, though the first version of our M16 selector did use the milspec and could also be over-rotated.  In this case, the detent holes of a semi auto selector should not look like those on an M16 selector.

Top two are Battle Arms Dev. selectors, bottom is cast, unknown brand M16 selector


Battle Arms Dev's redesigned detent hole depth and angle, groove depth and angle, and shoulder depth

nice pics Duffy. you really can see the difference. thanks

Thank you  Pictures often show details that escape naked eyes