Revised version, double the units.
The trick this time, and what I should have picked up on a year ago, is to only check collisions on units that are ready to shoot
This example uses no extensions and no fastloops, so no ForEach. Believe it or not, MMF's built-in box collisions are BETTER than using ForEach with custom box collisions as in my previous example, even with the tweak described above. Surprised that using overlapping collision masks to do distance checks is now faster than using math. Thanks Clickteam!