I just had my Accushadow 2 milled for the CZ Custom RDS plate system. Yes they mill into the firing pin channel. The plate actually has a firing pin groove milled into it to cover the firing pin. The RMR/SRO plate I received is a steel plate, it is tightly fitted to the slide (have to tap in from left to right like you would for a rear sight), the extractor pin is inserted to help locate it, and there are two flat head cap screws that also locate it. I'm not sure there is a wear risk associated with this application? The firing pin just needs to be captured and not bind up and CZ Custom doesn't mill it deep enough for the pin not to be captured in the slide without the plate covering it (i.e. even without the plate installed the firing pin is retained in the slide). One thing I will point out is that the milling isn't flat front to back on the slide, they mill it deeper at the front vs the back. Thus the rear of the pin is fully captured and the front of the pin is fully captured.
I'm sure by this point there are shooters out there that have put 10's of thousands of rounds on this plate system. If there was an issue it would have been identified by this point. I don't have but maybe 500rds down range with my Accu2 thus far but will be testing it's longevity over time in USPSA.
The tangible benefit for milling this low into the slide is that you get the optic mounted as low as possible with a interchangeable plate. I have the fixed sight plate so I can swap between carry optics and production at will. My SRO could maybe be lowered 2mm lower and still clear the top of the slide. That is close enough for me and I'm an Iron sight shooter for the last 8 yrs.
Cheers,
Toby
