A siren build for when you don't want to see any more builds with murms. HPPC+2UAC5 for long range efficiency, 3ERML to have a 400m optimal range of pinpoint destruction. UAC5 doesn't quite have the pinpoint of AC20 though I suppose.
So far this is just theory crafting. I've been using this with an MRM40 rather than a HPPC to some success though.