That's where the XXL comes in, for the new version of the game coming to XBLA later this summer. The new game has an extra suffix (Serious Sam Double D XXL) denoting new content, and one big aspect is Gunstacker upgrades! There will be two types of modifications "Ammo" and "Upgrades".
For each of the 8 gun types (Tommy Gun, Rocket Launcher, etc), there is the ability to increase the amount of ammo the guns can carry. This general modification is applied to an entire 'gun type' (like all variations of Tommy Guns). As you buy Ammo+1, you get an extra clip which gives you about 20% more ammo for that gun type. Any Tommy Guns for which you buy Ammo+1 can now carry more ammo. That opens up Ammo+2, and then Ammo+3, each costing more, but letting you carry a lot more bullets in the end.
|Buy gun-changing upgrades for particular guns.|
These range in complexity, from an upgrade to the Machine Pistol that increases the damage dealt by all guns in your current stack, all the way up to entirely new weapons like an upgrade to the Shotgun... that turns it into the legendary Serious Sam Cannon!
You'll also be able to revert a specialty gun back to it's original form, and get a little bit of money back in the process.
Stay tuned, as over the summer I'll be detailing some of the various new guns you can get in XXL.