"...is that a mark five or a mark six?"
The Force lance, also known as an F-lance, and Lance, is the standard issue sidearm of all Commonwealth officers. The Force Lance generally looks like a metal rod approximately 30 centimeters in length capable of firing plasma shots and smart bullets which can find their targets from almost anywhere in the proximity of where they are fired. The weapon can extended to almost 2 meters and be used as melee weapon to disable or spar with opponents. The lance is keyed to its handler's DNA, meaning that if an individual who is not the assigned user of the weapon will be incapacitated by an electric shock should they pick it up, although there are inconsistecies to this security feature; or maybe this feature is only made available to high guard Captains. (”The Risk-All Point”)
Also to be mentioned, there are instances in which a lance can be operated by remote; someone with the right codes is capable of causing a force lance to discharge either by voice, pulsed laser or microwave transmission. Whilst fully extended in melee mode the lance can not only continue to fire but can also act as a taser delivering an electric charge from its opposite end. The energy capacitors within the lance responsible for this can also be set also for a single high energy electric discharge capable of shocking multiple enemies simultaneously.
The Force Lance can launch a number of self-guided tiny attack drones, called “Effectors”, that both target opponents and intercept incoming projectiles. In addition, a grappling hook attachment can be fixed to the firing end of the lance, allowing the user to create a make shift zip line when needed in ”Una Salus Victus”. It can be used as a grenade launcher. Also, when the lance is placed in a stationary position, it can be set on auto fire or artillery intercept mode. Adding to its already long list of capabilities a force lance can serve as a plasma grenade when set to overload.
Because of their versatility, Force Lances became profitable items on the black market after the First Systems Commonwealth Civil War.
The force lance appears to be capable of extending from only one side as seen briefly in "Exalted Reason, Resplendent Daughter". We see Dylan utilize this feature in a fight with the infamous Kulis Bara to defend against Bara's . This seems to be the one and only time this particular capability is seen in the series and so it is unclear whether or not all force lances have this option or if this is a custom modification made by Captain Hunt.
Due to the fact that the force lance fires both smart bullets and effectors it stands to reason that the weapon would need to be reloaded, the process by which a force lance is reloaded is largely unknown. However, in "Home Fires", Dylan is shown firing his force lance at Telemachus Rhade, then diving behind cover and performing some sort of cocking maneuver by twisting and pumping his force lance, though the device itself does not appear to have any obvious points where a magazine or energy pack might be attached. In ”Dance of the Mayflies”, the Bokor are killed by an electric shock which a force lance could only generate 3 times. After 3 shots Hunt used another lance. This implies that the energy source is not meant to be recharged or replaced during combat.
In ”All Too Human”, we see Rommie wielding what appears to be a tonfa style variant of the force lance similar to a police baton. This is the only appearance of such a weapon and so its exact specifications or whether it's a kind of force lance at all is unknown. What do know of the weapon is that it appears to operate on similar principles as other gauss weaponry and can be used to intercept incoming projectiles however it is unclear whether this is achieved through the use of effectors or the physical impact of the weapon with the incoming fire.
The force lance comes in two different color schemes. The first seen mostly in season one is a shade of gold/copper with hints of red at both ends of the weapon. The second variety from seasons two through five is the commonly seen gray/steel and black. In terms of functionality there does not appear to be any differences between the two types meaning that the aforementioned color schemes differences are purely cosmetic.
While it has demonstrated light generation features in ”To Loose the Fateful Lightning”, it is not clear whether Harper's statement the weapon has scanning features is in fact correct as such capabilities are never seen in the series.
In ”The Devil Take the Hindmost”, the leader of the slavers remarks "...is that a mark five or a mark six?", regarding Dylan's force lance. This suggests that the High Guard used the lance as its primary side arm for quite some time making a variety of changes as new technologies became available. Unfortunately these other models of force lance (marks 1-4) are not depicted on screen and it is unclear whether the "mark six" is the latest design. However from another perspective the different design designations might refer to different specialized variations (ex: a sniper model, a grenade launcher) instead of advances in technology.
"The force lance is the High Guard's favorite toy. Retracted, it can be used as a light source or a scanner or whatever else comes to mind,and deployed, it makes a nifty quarterstaff or, uh, limbo bar." -- Seamus Harper, ”All Great Neptune's Ocean”