Caliber: 9mm Action : Rotating Barrel, Stays open after last shot. Sight : Adjustable Barrel : 4" Mag : 15, 30 Name : TMP = Tactical Machine Pistol, SPP = Special Purpose PistolSteyr's answer to the HK MP5K. This gun is mostly polymer from magazines to receiver. The person responsible for the design of the TMP/SPP formerly worked for Glock inc. Glock polymer handgun Steyr polymer submachine gun, You get it. The TMP is however in no way the only polymer firearm manufactured by Steyr, the AUG rifle is another.
The TMP/SPP is a cross between an UZI, AR-15 and Colt 2000. The magazine seats inside the handle like the UZI. The charging handle is similar to that of a AR-15. The ergonomic handle and rotating barrel were borrowed form the Colt 2000.
The TMP has a vertical handle as part of the polymer receiver. It had to be removed from the SPP because BATF doesn't like the looks of it :). The TMP/SPP both have threaded barrel shrouds but in the case of the SPP there is a permanent finger(shooter's)/tread saver attach, actually glued on (don't tell BATF). The treading is there to accommodate a silencer.
The barrel is located low to the shooters hand. This allows better control of the firearm. The TMP/SPP's approach to keeping the chamber close until the bullet exits the firearm is to use a rotating barrel. The barrel is free to rotate locking the chamber when closed. A bullet traveling down the barrel rotating cause by the rifling, transfers it=B9s rotating energy to th= e barrel keeping it lock. When the bullet exits, the rotating energy is no longer there keeping the camber closed. That is the best I can do in explaining it.
The charging handle is located to the back of the firearm and pulls straight back. This setup is straight out of a AR-15. Good for left and right handed people.
The sights are adjustable if you are patient. The rear sight adjust for windage and front sight adjust for elevation. To make things worst you can only adjust the front sight after breaking down the gun. There are slots on the firearm that makes attaching and removing a Steyr scope mount easy.
The complaint I here most often about the SPP is that it has a long trigger pull. There is a reason for it. The TMP has a two stage trigger with the first stage being semi-auto and the second stage being full-auto. There is no select fire switch to set. The TMP inherited its fire selection system from the Steyr AUG. Seeing the SPP is the semi-auto version of the TMP, Steyr just change the trigger setup so that it would only have a single semi-auto stage. That is why the trigger pull is long on the SPP.