Gamma World's current ammo rules states that you either have ammo or you don't. If you have a gun, you have ammo. If you fire your gun once per encounter, you're conserving ammo and at the end of the encounter, you still have it. If you fire your gun more than once per encounter, you are not conserving ammo and will not have it at the end of the encounter. Additionally, ammo is an abstract, generic concept. If you have any sort of ammo, you can fire any gun.
While this rule vastly simplifies the game, it tends to make mundane gunfire a bit less fun. While you can fire your gun wildly during an encounter, you may as well keep firing it every time it's your turn. Not many people will be content with just firing the gun once then putting it away for the next fight.
I also believe that finding a laser pistol, a shotgun, a Colt .45, or an M-16 something that can happen in the game, I don't like the idea that there's one generic ammo pool that covers them all.
I am therefore going to propose the following house rule dealing with gun fire and ammo. The idea is stolen from another blog
You may fire your gun as many times as you want during an encounter. However, if you roll a natural 1 on your attack roll with a gun you have 2 choices:
[REWARD] 1. You can accept the 1 and miss or
2. You can re-roll the result and run out of ammo.[/REWARD]
When it comes to ammo type, I am going to leave it up to the player to associate the ammo found to the gun that uses it. The ammo now only works with that particular gun. This means that I will allow players to carry extra ammo other than the generic type described in the base rules. If you run out of ammo, it is ammo for that specific gun.
What does this mean? It means that if you find a gun that requires energy clips in order to function, then the ammo you record for that gun is considered energy clips. If you find ammo and assign it to a sawed-off shotgun, that ammo is now only available for shotguns.
The above two house rules should make the game slightly more realistic and I think a bit more fun since you can now fire your mundane weapons more than once per encounter and still retain your ammo. That is, of course, if you don't roll a natural 1 and then re-roll your attack...
I will, however, have to modify the Pure Strain Human's powers since the new ammo rules functionally debilitate the origin's utility power.