BT or Ben Tippmann Paintball Design is a company that produces Mil-Sim paintball markers.  One of their barrel modifications includes the APEX barrel system, Rip-Clip Loader System.  This is similar to the Flatline barrel system but can be directed up, down and even sideways.  Their guns are similar to the Tippmann A-5 and 98 Custom.  The line-up of the BT-4 includes the Assault, Ironhorse, Delta Elite, Combat, Banshee, and SWAT. One of the high-end markers is the TM-7, a low-pressure paintball marker.  Unlike the BT-4 that is modeled after the M-16, the TM-7 is modeled after the MP7 by Heckler & Koch.  BT and Tippmann’s are commonly used for police training and even crowd control because they can be utilized in close quarter combat situations with no possibility for fatalities, when properly used.