Shotguns (Point and Shoot). You aim with your finger with a shotgun - What I mean by that: Essentially you have your target, and fire in its general direction. You're bound to connect with it if you are fast enough.
(I am an avid trap-shooter: With any shell that fires pellets, just remember to have that knee ready and the gun partially down, the follow-through with the shot is usually by finger/pointing with your fore grip.)
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The reality is that in any dense forest/jungle - Optics are as good as Iron-Sights. Solely because you're fighting on top one another, and in reality, if you focus too much on just one target you're bound to get flanked and most likely ripped to shreds; both eyes open at all times and point with the barrel...
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Now getting into the more advanced systems - heat/thermal, etc. A whole different ball-game.
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As for what Magnum said, it is pretty prevalent to see sights on a SAW and rifle...Both Aimpoint and Acog... If the armory has it and their unit is the creme de la creme of the fighting forces, they usually get cooler #%&*$#. (or elected to test out new gear...)
So whichever way you go with it, try to place the type of battle, with the type of unit, and factor in remoteness/scarcity of assets/bases. - Then take into consideration those factors and see what can be used and what would be realistic in terms of the scenario.
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RIP Kevin "Positive G" Speichts