The Gunslinger has the following stats:
- +25 max HP
- No random critical hits
- Sentries Guns are replaced by Mini-Sentries
I'll explain each point in order.
The Gunslinger does not regenerate HP; rather, it seems more likely that they just meant that it gives the Engineer a larger total health pool.
In order to compensate for the additional HP, the Gunslinger cannot roll for random critical hits. However, it is able to strike a guaranteed critical hit upon the third consecutive hit on any enemy. You can hit different enemies, so long as you don't let go of your attack button. Note also that since this is a guaranteed critical hit, it works even on
Finally, equipping the Gunslinger replaces your ability to build a Sentry Gun with the ability to build the Combat Mini-Sentry Gun. The Mini-Sentry will build much faster and starts with a full health bar instead of the partial HP of a normal Sentry. It also costs 30 less metal to build at just 100 metal, and shoots 1.5 times as fast as a Level 1 Sentry Gun, or 0.75 times as fast as a Level 2 or 3 Sentry Gun. However, each shot deals only 50% damage, resulting in a lower DPS than normal Sentry Guns. The Mini-Sentry also cannot be repaired or upgraded, meaning that damage dealt to it is permanent. Its lower health pool of 100 HP means that it can be destroyed in one shot by a Direct Hit rocket.
The Gunslinger also provides access to a kill taunt, which can be used even during Humiliation or Stalemate.