System advice. Which do you use?

[Michael Lewis]

What rpg system do you use for a post-apocalyptic style game such as Twilight 2000 and why?

A little history:

I've had the original Twilight 2000 rules since it first came out. I've read some criticisms about automatic fire rules and the vehicle combat being too complex. I discovered 2013 and loved the count down turn system. We tried to play a session or two but no one enjoyed the complexities and it seemed like you needed a detailed map for every combat.
I found Gun Master, which is based on Harnmaster with it's percentage base and no H.P system. I read up on Harnmaster III then Gun Master. There seems very little support for it so I don't think it would be worth continuing it.

That is my quandary. A good system that allows for tactical play but is not so difficult to teach to newbie players.

Michael