Blood and Rust

Gyro-weapons are Photos ballistic weapons that are on a hand-held scale. They function on the Gyrojet principle in that a projectile, rather than being propelled by an explosion in the chamber of the weapon, is self-propelled; in the real versions of the weapons they had two thrust ports that spun the rocket as it flew; in any case the projectile is gyroscopicly stabilized (I misspelled Gyro as Jyro >.<), and the rounds explode; in real life, this didn't really have any more stopping or penetrating power than a regular bullet but they were marginally more expensive and the later model firearms had a barrel defect that caused their normally-high accuracy to severely drop, to the point that it was almost impossible to hit anything with them. As such the project was dropped and it faded into obscurity. In almost all instances they're caseless, but some weapons (Such as the Bolter/Boltgun from Warhammer 40k) use a standard explosive charge to propel the shell out of the barrel before the engines kick on; in reality this would be rather stupid because
A)The explosion of the cartridge would likely destroy the engines and simply have the round travel as a needlessly heavy shell that wouldn't go more than a probable few feet.
B)The rounds accelerate as they travel under power meaning you'd want the engines on as long as possible to build up velocity; the force of the expulsion, then the engines kicking on would likely make it hard to gauge the starting velocity of the round and make leading a moving target very difficult.
All Photos ballistic weapons are used under the Gyrojet principle, be it an autocannon, an artillery gun, or a handheld weapon. The Gyroweapons used by the Photos infantry are usually large bore and high-yield to actually be competitive with their ubiquitous plasma weaponry. The weapon in this case, the Gyropistol, is about 15mm in bore; it's big. That's why most handheld gyro weapons are in Opairis control, sense they're bigger, stronger, and overall just able to make best use of the weapons.
In comparison to your standard plasma pistol, a Gyropistol provides around the same armor penetration ability but much greater stopping power due to the fact that the round explodes rather than just penetrating. Against a human size target one well-placed shot to the abdominal or chest area would be sufficient to kill; the explosion would likely rip you open and rupture most of your organs in the general vicinity, if not outright destroy them. The entire function is one-shot-kill. Against a larger creature, again, a well placed shot would suffice. face or chest vicinity is going to at least incapacitate it for the soldier to either fire again or kill it with a melee weapon.
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Sorry for the brick of text but I'm bored out of my mind with nothing better to do >.>