I run out of Handcannon ammo all the time, please don't reduce it any more! There is already a catastrophic difference in reserve ammo between Handcannons and Scout Rifles. Reducing the reserve ammo on Handcannons may even bring them to the level that Auto Rifles are currently at (crap-level)!
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Be sure to obtain armor that increases the amount of hand cannon ammo you have and increases reload speed... After that, there isn't much to do... I too am saddened by this :(