Just considering guns today (as you do...) and I was thinking that some of the rules don't quite work for me.
Consider Autofire: You spend 6 seconds to fire between 3 and 30 rounds from your weapon. If we look at an AK-47 (a fairly ubiquitious AR), with it's 600RPM firing rate, you can accomplish that in 3 seconds max - and no one ever burns an entire mag (unless they're rollplaying someone with no real firearms training). That's before we talk about weapons with either a higher rate of fire (proper machine guns) or modifications that can up the firing rate substantially (I've seen a 750RPM AK-47 on discovery channel and a micro Uzi @1000 ). The penalties are also pretty huge (representing recoil and muzzle climb) - but what about weapons that are bolted onto 5-6 tonnes of truck? I've seen guys firing full auto mounted weapons and getting groups the size of a rockmelon (canteloupe to some?) - so the -10 to hit anything at all seems a little off there.
I'm not sure what the best solution for that one is - GURPS has RoF rules, which for a cinematic game are probably a little too much to bother with, so I'm not sure that's the solution. Dropping Autofire to a half action would work for 99% of application (I can't think of any weapon you can Autofire that has such a low RoF that a half action becomes a problem - not off hand anyway).
Strafe has the same issues as Autofire really. Again, I think the penalties (increasing Defence in this case) are a little too harsh - especially with weapons that are designed to mitigate the cause (mounted weapons, emplaced weapons etc).
I think a big part of what I'm pondering here comes down to - is it possible to have recoil rules that are quick, easy and work properly? The SC2 recoil rules basically got thrown out for anything that wasn't insane by my group (burst firing a .50 Desert Eagle for instance would be "insane"). But if something that works could be figured out I think it'd be a great benefit to the game - you could put precision small caliber, low recoil, fire onto a target rapidly, but it would be far harder to do it with a large caliber weapon (MP5 vs Thompson / AR-15 vs AK-47).
My off the cuff thought about that was build it into the guns stat line - M-16: Mode: Single, Burst (3), Auto (30/3). To break it down - the weapon can fire in single shot, a 3 round burst, or autofire up to 30 rounds as a half action with a recoil value of 3. The recoil value means that each successive shot from an autofire hits for each multiple of 3 you exceed the targets defence. Higher recoiling weapons will have higher values.
I think cover fire and supressing fire could be combined into one action - they serve the same overall function, especially in tactical/joint actions. One guy runs to an objective / downed ally while the other one lays down supressive fire on some hostiles that are attacking the team. The hostiles make their morale check to avoid the penalties, and if any of them leave cover they might cop a bullet. Easy. I'm ok with this being a full round action, taking multiple bursts of fire from the user (in fact I'd up it's ammo cost too) - it fits what the person is doing with their time thematically.
(Sorry for the long post, I had a short discussion with a mate at uni and well here we are...)