I think you are feeling the roughness of the hammer face and the drag of the hammer face on the bottom of the bolt group. This is how the PS90 cycles from a fired setting.
1. The bolt group moves rearward and the rounded rear edge of the bolt group cocks the hammer which allows the auto sear to engage into the hammer notch. This happens in the first 60% of rearward movement of the bolt group.
1A. You start to feel a heavier resistance.
2. As the bolt group continues to move rearward, the bolt group bottom slides against the hammer face for about the last 40% of rearward movement. This can be felt as you manually cycle the firearm. For about 60% of the initial rearward movement, there is hardly any felt resistance. You then feel a hump as the bolt group drags across the hammer face and the last 40% of movement you can feel the drag.
3. As the bolt group moves forward, the initial 40% of forward movement you can feel the drag of the hammer face on the bottom of the bolt group. The remaining 60% of forward movement, there is no resistance as the bolt group has moved forward enough that it no longer is sliding against the hammer face.
4 When the bolt group moves forward, it strips a round from the magazine and the continuing forward bolt movement chambers the round. At the very last bit of forward movement, you will hear a click. This click is the auto sear being tripped.
5 The cycle repeats once the trigger is pulled, the cartridge fires, and the bolt group moves rearward ejecting the spent cartridge. Back to 1.
To hear and see this movement, you can do this.
Remove the barrel group.
Remove the bolt group.
Remove the butt plate by sliding it up.
Replace the bolt group.
Replace the barrel group.
You now have an assembled firearm without the butt pad installed.
Get a small flashlight or other light source that allows you to see the top of the hammer pack and the back of the bolt group, looking into the rear of the firearm from the removed butt pad. I use a small flashlight held in my mouth so I have both hands free.
Looking into the rear of the firearm where you can see the hammer pack and the rear of the bolt group lit by the flashlight or light, you can now manually cycle the firearm and see and feel how the bolt group cocks the hammer and then you will also see and feel how the hammer face rides the bottom of the bolt group for the last 40% of cycle motion.
This is normal.
What I think you are feeling is the face of the metal hammer riding the bottom of the bolt group during that 40% of rearward movement.
I think your firearm is OK. What I would do though is contact Man Kave and buy a new polymer hammer and replace the aluminum hammer. Or if its the short pull hammer, buy a new one. If he is OOS on the blue hammer, I have one sitting in my safe.
I would not have filed the hammer face but the bolt group is a much harder metal so the aluminum hammer will not damage it as the bolt group slides over the hammer face. Eventually, the hammer face may even smooth out again.
Let me know if this is what you are feeling cycling the firearm. But as I indicated, it is probably nothing to fret over.
