My concern would be this. If you “pre wear” the stop mechanism by sanding and polishing. To the point that insertion of a mag will allow the slide forward. How long will it be in use before the stop wears down more and it will no longer hold the slide open when empty?
Having adjusted slide stops to auto-forward on almost two dozen pistols from various manufacturers and shot most of them for thousands of rounds, I can assure you this is not an issue. Once a proper adjustment is dialed in, the two mating surfaces actually engage more than the OEM offerings, providing sufficient friction to hold the slide back without the stop lever slipping down. The action of depressing the lever is made easier because of polishing, not because of reducing friction alone. I have not found enough further wear between the two, smooth mating surfaces to change the function.
If it were to become an issue, simply roughing up the slide stop engagement surface, IOW adding back a little friction, would solve the problem in a few minutes. If the failure occurred at the worst time, the response is simply a trained failure drill. Remove (empty) mag; insert loaded mag; overhand rack slide.
When talking about slide stop/release manipulations, I find it helpful to use correct terminology. The "slingshot" method of retracting the slide describes pinching the rear of the slide between the thumb and forefinger, as if shooting a slingshot, to retract the slide. This is rarely what is taught nowadays for defensive manipulations.
Rather, the "Overhand" method is what is commonly taught. The slide is gripped with the lower palm and the opposing fingers of the off hand. This gives more friction and generally allows for a firmer grip, especially when pulling against stiff recoil springs.
The nit picking over slide "stop" vs. "release" is the same. We generally know what a person means using either term, but clear technical writing helps everyone understand the action description the same way.
Auto forward has never failed to load a round from a loaded mag, slide locked back, for me in a defensive gun. However, I've had some failures to feed in .22 pistols using this method. Releasing the slide using the adjusted stop as a release always works. Using the overhand or slingshot method always works.
Despite using the auto-forward method successfully, I also hit the slide stop with my off hand thumb on the way to reacquiring my two handed grip. If the slide does not drop from simply inserting the mag smartly, dropping the stop definitely releases it. If it still does not release my default is the overhand method, just as it would be for any malfunction.
The need for a speed slide locked reload in a civilian gunfight is extremely small. Practicing it is useful, but it is a lower priority for me than the many other more important skills needed while emptying that mag.
When being concerned with speed, nothing is faster than auto-forward, as long as it is reliable. Most people refuse to do it because they can't imagine it can be so quick and reliable.
The next fastest way to a reload is dropping the slide stop while reacquiring a firing grip. It is the method used by almost all competitors and many tactical folks.
The slowest method of releasing the slide is to take the extra time and movement of the offhand to overhand or pinch the slide. Especially the overhand method is not foolproof, as it can result in "riding" the slide, getting something (glove, skin) caught in the ejection port, and for some guns is made more difficult by sharp, tall rear sights or a red dot sight. Nothing is foolproof. No one method is right. What works for you is what is right.
Auto-forwarding works reliably for me. The back up use of the slide stop as a release guarantees that the slide will go forward, barring some other unforeseen interference. I wont buy a FS 2.0 M&P because of the company's mechanical interference with the various, appropriate and reliable alternate uses of the slide stop lever. Forcing me to change my reload method of over 20 years is something I do not like. No other manufacturer does it. It is not a feature; it is a poorly contrived, unnecessary inconvenience.
