I've been tinkering with an idea revolving around modules that increase your maximum ammo capacity for a given weapon. Originally, I attempted to draft an idea for a module that grants flat percentage increases to all weapons; this was very difficult to balance as 10% more ammo for an HMG is significantly more useful than 10% more ammo with a mass driver.

In the end, I separated the modules into the core weapon types: explosive, laser, hybrid - rail, hybrid - blaster, projectile. Weapons that feature small ammo capacities (explosives) were given a flat increase in the number of carried rounds. The CPU/PG requirements were taken from tanking modules' PG/CPU with a 25% increase. The Extended Ammunition Module skill then reduces the fitting requirements.

Submitted for your approval...

PG/CPU requirements should be low/nonexistent for something like this...

Way too weak, but good idea. I wouldn't use an entire module slot for an extra magazine, especially when it uses that much resources. Needs to be A LOT more powerful, so that Nanohives don't make them useless. At least 75% for Basic Tier. A Compact Hive is way better than even your the complex suggestion.

Shouldn't use that much CPU/PG. Maybe this could be the first PG-only Module,in the same way that some modules don't use PG, this might not use CPU?

You have to remember that modules like this would be competing with things like HP modules, Regen Modules, and even Nanohives. They have stiff competition, and they'll need to be really useful to actually be worth equipping. Not a niche thing.

Could you fit Flaylock into the Explosive weapon category as well. It seems to be missing, unless I missed why it is missing.

-snip-

UPDATED OP WITH THIS...

I have also considered the idea of making this module fit into the sidearm slot: instead of carrying a sidearm, you are opting for even more ammo for your light/heavy weapon. Would like your feedback on this.

I would prefer H/L as you have it or even reversed.
As a Sidearm Slot it cuts out most Logi from the upgrade ( I feel it should be an option to all suit types)
As a Sidearm enthusiast (most of my SP in weapons is in Sidearms) this cuts sidearms out unless you only want to run one.
We need more valuable High Slot options.

The reason I think reversing the H/L system you have is to give competitive options against preferred HP mods by faction. This may not be a good idea though, as People in Dust seem to prefer Tank over Gank.

The slots should stay like that. Modules like this might help to decrease dual tanking.

I've been tinkering with an idea revolving around modules that increase your maximum ammo capacity for a given weapon. Originally, I attempted to draft an idea for a module that grants flat percentage increases to all weapons; this was very difficult to balance as 10% more ammo for an HMG is significantly more useful than 10% more ammo with a mass driver.

In the end, I separated the modules into the core weapon types: explosive, laser, hybrid - rail, hybrid - blaster, projectile. Weapons that feature small ammo capacities (explosives) were given a flat increase in the number of carried rounds. The Extended Ammunition Module skill then reduces the fitting requirements.

I have no considered the ISK cost of such a module, but I would prefer to keep it very inexpensive even at proto levels.

I have also considered the idea of making this module fit into the sidearm slot: instead of carrying a sidearm, you are opting for even more ammo for your light/heavy weapon.

Submitted for your approval...

0 CPU 0 PG, just like the Vehicle Variants. Then im happy for this.

Only issue would be the point of the Ammo Capacity Skillbook. Why get that when I can use a module?