This is in my series on Paintball guns. You can find the introduction here.
The design is very gun-like to make it easy to use for lumberjacks who are familiar with real firearms. The method of shooting, however, is very clunky and slow. The left handle plate is removed, the CO2 cartridge is inserted into the handle, the small ring at the bottom is turned until the cartridge is pierced and ready to use, and then the handle plate is replaced. This process is fine for its intended purpose of marking trees, but when its primary use turned to marking other players in the survival game, reloading became an extreme hindrance.
Also, to re-cock the marker after every shot, the knob at the back of the body (the bolt) must be turned and pulled back against the mainspring, the gun is shaken to allow the ball to fall from the top storage tube into the barrel, and then the bolt is shoved closed and turned back to rest. This process easily takes three or four seconds. Again, this is no big deal against trees that cannot shoot back, but against other players, it means that every shot must count, because the next won't come for a while.
To bypass some of these problems, many players modified their markers. The most common modifications were the addition of a "speed wheel" which allowed a much faster change of CO2 cartridges, and a pump handle that greatly sped up the re-cocking process. Equipped with these two modifications, a player could fire about one shot per second. This increase in firepower was amazing at the time. However, compared to modern markers, this technology is horribly out-of-date and clunky.
Here is an example of a modified NelSpot. Note the speed wheel at the bottom of the handle and the prominent pump up front.