The problem I have is more that you can't use any other ammunition type, and the base availability of them makes prohibitively expensive at character creation.
Ditto. Hence, my houserule:
High Powered Ammunition is not a separate type unto itself; many kinds of ammunition are available in high powered ("HP") variants. (Disallowed HP ammunition includes Stick-and-shock, Capsule, Gel, and Subsonic.)
Firearms must be modified to fire such rounds, and once modified can fire
only HP ammunition. Any firearm, including assault cannons, can be modified in this way. Modifying a weapon to fire High Powered ammunition costs 2 slots, has a threshold of 20, requires an armorer's shop, and costs as much as the original weapon (with an availability of 7R). This modification is incompatible with Extended Magazine and Increased Cylinder.
HP ammunition gains +1 damage and -1 armor piercing, in addition to the base values for that type of round. Price is multiplied by four, and availability increases by +8. When fired, all recoil is doubled before compensation. Additionally, HP ammunition is especially loud and has a large muzzle flash. Attempts to detect or pinpoint the firing of HP ammunition gain +3 dice for hearing tests, or +1 die for visual tests (these modifiers are cumulative with silencers / suppressors).