There are various versions of the trigger frame and how the autotrigger cam is held in.
Pull your grip frame off and look at it from the top side.
On the side topside closest to the AT cam, there may be a small hole. If there is, then it would either use the old style of having a spring and BB to hold the cam in, or the current style that uses a pin that holds the cam in.
The other type doesn't have the hole that retains the cam, for those types, it was held in purely by pressure and the screw that is on the pump rod.
Hope that helps.