Well Hell,
the deeper I clean this SACS Nina, the more I find.
I have not shot this piece in yearss, and when I dug it out it was dirty.
I replaced the firing pin stop, the plunger tube detents and spring (spring felt soft).
I have 24 mags for this gun (definitely overkill), and they are the Springer 9 rounders. I can't recall the manufacture.
This gun was built in 2011 by SACS and I have over 10K of target style or 147 TMJ trouble free rounds through.
What I have notice in inspecting and cleaning is the jagged or rough feeling of the engagement of the slide stop locking the slide to the rear.
I tried several dry empty mag slide lock backs and the slide stop barely catches the slide. Well, there is a slight rolled over edge on the slide stop notch cut out.
When I try to push the slide stop to full engagement with the slide, its rough but only the corner is missing Armory Kote (the finish). The rolled over edge is on the bottom of the slide not in the notch.
12 of my mags were dirty, so I cleaned them all hoping to see an improvement of slide stop engagement with the slide. NOPE!
My slide stop is factory MIM and I noticed several mold lines on the back face. Hey maybe those are adding to the rough engagement.
I began stoning that area to flatten the lines, but it's a crater and did not want to waste my time. F it, I ordered a EGW 9mm slide stop.
It appears this issue might have been slowly showing itself, but I never caught it till now.