If you have never studied on how the P22 works internally or disassembled one the above picture might help. What I have done is remove the slide, grip and left side of the frame. I've also removed the mainspring and sear spring. Why??? Because it is hard to position everything for photos while fighting springs.
DA pull. On the very far left you can see the upper portion of the trigger and the trigger spring. Here a magazine has been inserted in order to press the magazine disconnect up and away from the top of the trigger bar. All the safety does is press down on top of the trigger bar which keeps it from being able to rise and engage the hammer strut and sear. The two expanded tabs on the front of the magazine press it upward and disengage it.
As pictured what is happening is that the light weight trigger spring has lifted the rear of the trigger bar causing the center portion of it to engage a slot on the front of the hammer strut. This is essential in DA since pulling the trigger moves the trigger bar more and more rearward which causes the hammer strut to rotate the hammer more and more rearward. Notice also the leg sticking up at the rear of the trigger bar. There are two. These engage the two bottom legs of the sear and rotate it out of the way of the falling hammer. It is essential that the trigger bar spring be strong enough to hold the rear of the trigger bar up.
Next, notice the slanting steel pin on the right side of the frame half and located under the sear. As the trigger is pulled more and more, the hammer is rotated more and more rearward. So when and how is the hammer released in DA. First, the sear is never engaged with the hammer. The sear is rotated out of the way and kept out of the way. The hammer strut is being pressed rearward by the center portion of the trigger bar. As the trigger bar moves rearward the outer shoulders at the rear engage the slanting steel rods. These begin to make the rear of the trigger bar slide downward until the center portion releases the hammer strut. The hammer falls and the pistol fires.
In SA the sear actually has caught the hammer on the primary hook and is holding it fully cocked. In SA, the legs on the top, rear of the trigger bar physically rotate the sear counterclockwise causing it to disengage from the hammer hook. The hammer drops and the pistol fires.
In both modes the trigger bar holds the sear out of the way of the falling hammer and continues to hold it there until narrow ramps under each slide of the slide hit the trigger bar ears which knocks them/trigger bar downward and disconnects it from the sear. The sear then rotates very quickly to catch the hammer in the cocked position. The sear is spring loaded to press against the hammer at all times unless the rear trigger bar legs engage and rotate it away from the hammer.
So, SA release is by the real sear while DA release is by the rear center of the trigger bar sliding off the bottom of the hammer strut. I did a whole thread on this with more pictures but photobucket threw us under the bus and while I still have them hosted elsewhere I have never put them back into the thread. I need to do that.
The point of all this is to show the complexity of timing of the various actions going on inside of the pistol and why you have to be really careful before modifying things. From what I see, removing material from the rear of the exposed trigger would not benefit anything nor would it have any effect on the timing of release of the hammer in DA or SA. The hammer spring is 8 lbs and below 7 lbs you will begin to get light strikes...so, weakening the mainspring is not a good idea. I've done all of this in the past and there are threads on what I learned. I do polish the outer top edges of the trigger bar to make sure they slide down the steel pins with as much smoothness as possible but to be honest....I never felt any difference and don't fire much in DA to begin with. 1917