The compressed main spring forces the hammer back until it reaches the rear of the power tube and provides enough energy to force the power tube back. As the power tube is pushed back the valve opens and compressed gas flows through the power tube and the tuned port compensator (TPC), projecting the paintball out of the barrel. Design The term Nelson-based lends itself to the Nelson Paint Company and its first marker, the Nel-Spot 007. The basic valve design found in these early markers laid the groundwork for many other manufacturers to develop their own paintball guns. The Nelson design is in-line which means that the bolt, hammer, and valve follow the barrel and form a line as opposed to being stacked. It fires from a closed bolt position meaning that when it fires the bolt is secured into the breech end of the barrel with a paintball loaded. In comparison, the bolt in an open bolt marker is not secured until the marker fires, at which point the paintball is chambered, fired, and the bolt is then re-opened. Another characteristic of the Phantom that varies within the Nelson-based family of markers is that it features the original breech drop design as opposed to the bore drop variation of the design, meaning that the paintballs drop into breech, or rear of the barrel, rather than dropping into the bore of the barrel. Variants Different breech layouts allow players to use larger hoppers that are more common among contemporary semi-automatic markers or horizontal feed tubes. There are two styles available for the Phantom; gravity feed and stock class. Another feature which may differ depending on user preference is the grip frame. The two most common grip frames available for the CCI Phantom paintball marker are the .45 style and M16 style. The .45 is an offshoot of the common grip structure for handguns chambered for the .45 ACP pistol cartridge such as the M1911 Colt pistol. However, the .45 grip frame is a purely visual replica of its firearm relative as the Phantom cannot be fed by a magazine. The standard grip on the .45 grip frame is the government model rubber grip with finger grooves produced by Hogue Inc. The M16-style grip frame is derived from the structure of the rifle of the same name, the M16 rifle. The M16-style grip used in the Phantom is produced by Ram-Line