Absolutely loved this game. Don't get to play at all now, more's the pity. The reaction system is excellent and I always thought firing was realistic (caught in the open you are almost certainly dead).
John
Cheers! Yeah, it's one of those games I got on the shelf, only ever played it with one guy, he moved away (and out of wargaming altogether for a while as he was building a house for a bunch of years). Now he's back with a vengeance, but far away. It was cool though to play it again, because it's really good. That reaction system hits that sweet spot between 'gives plausible results via a plausible course of actions' (to avoid the world 'realistic') and 'fun'. Also, it plays so well.
Force on Force (okay, not quite squad-level, but also models firefights, close to the ground), does super plausible firefights, but you really have to wrap your head around them first to get to the 'fun' part in my experience. Great rules set, but wrinkles my brain.

Chain Reaction (or any other Two Hour Wargames game) of course is also really well known for its reaction system. Extremely interesting, because it's so unlike anything else.
The other squad-level firefight game I tried was Flying Lead by Ganesha Games (with a few bits from the Hearts and Minds supplement). I'm a big fan of Ganesha Games and their rules based on Song of Blades and Heroes. Flying Lead does a really good job, but for modern firefights I think I prefer having a reaction system in place. I mean Advanced Song of Blades and Heroes (excellent, my go-to fantasy skirmish game) adds a reaction system which can be implemented in any Ganesha rules set without a problem and works super well. But for frantic firefight-y stuff I think that the Operation Squad reaction system is superior.