It's my understanding the barrel trunnion of the MP5/10, .40 and .357 SIG are all the same. What I do not know is what the factory correct ramp angles are supposed to be? When compared to the 9 mm, the 5.56 and 7.62 NATO weapons, they all have a 50 degree ramp angle that the bolt interfaces with. However, the Special Weapons/Black Market Parts trunnions are 45 degrees. Does anyone know what the correct angle is and why the domestic equivalent for the same 10 mm, .40 cal and .357 SIG have a ramp angle 5 degrees different?