When firmly seated on the ground, range and azimuth can be adjusted using a control on the side of the weapon. As with a mortar, the grenade is simply dropped down the tube to prime and fire.

Impressions from the episode suggest the grenade has a blast radius of at least 200 yards. Captain Kirk fired a single grenade to destroy a Gorn landing party located on high ground about 1200 yards away - an officer present commented that using a projectile of such a yield at this short a range was risky.

So are we to assume that Photon Grenades are mini-photon torpedoes, containing an antimatter warhead? I'd hesitate to go that far: while the carrier for the grenades might contain a power source to maintain AM confinement, it seems risky for a ground weapon. Far safer (!) to think of the explosive as being nuclear in origin.

One note: curious resemblance of the grenades to the blue bombs used by the Gungans in Star Wars: The Phantom Menace!