By that logic anyone who is reloading should focus more on marksmanship than saving time during a reload.
You people have clearly missed the point. Racking the slide is a COMMON manual of arms. You do it when you load, reload and its the second half of your immediate action drill. The more you practice the better you will be. By racking the slide during reloads you are improving your manual of arms for executing an IA.
As for slide not returning to battery issues. That has nothing to do with using the slide over the slide lock. The SL only works if the last round has been fired and the SL is activated by a properly functioning magazine and isn't being ridden by the users thumb(s). The slide always chambers a round, its what its designed to do, whether the action sequence is done manually or automatically is of no bearing. Whether or not the magazine is functioning properly with regards to last round hold open is of no bearing. Whether or not there is a round chambered is of no bearing. Rack the slide you chamber a round.
You said it yourself that non ambi 1911's are difficult to use. Try running the slide lock on a sig left handed, they're near impossible right handed. Ever wonder why some slide locks are so small and their serrations stack like shingles? Its because they aren't to be used to release the slide, they're for manually locking the slide open.
Running the slide works on all autos for all shooters. Its also a common manual of arms. This equates to less time spent learning secondary operations. This means less to forget when under stress. This means you don't care what auto or what hand you shoot with as the method is the same. This means you can spend more time on what's important which is making hits. Using the slide vs slide lock is universal, anything else is specialized.
Tdc
While I have never been on a two way shooting range, I practice enough with my firearms to know what is going on with my firearm. I prefer to use my firearm as designed, rather than using a generalized procedure that may not be ideal for the firearm I am using.
With the 1911:
If the magazine does not catch the slide release the hammer will fall on an empty chamber. Pretty obvious what to do here, drop the magazine, insert a fresh one and rack the slide.
If the slide locks back on an empty magazine, drop the magazine, insert a fresh one, as you are bringing the gun onto target release the slide with the support hand as you get locked into your grip. Sights should be lined up on target, take your shot.
Yes, marksmanship should play a role here as well, if you have to rack the slide with your hand that is extra time that the sights are covered up and more time to stabilize before taking a shot. We're talking fractions of a second here but it does add up. The other point of marksmanship is this, if you are using your pistol for suppressing cover and you are wildly firing I think the situation is pretty well gone tits up. If you're using your pistol, you're only carrying one or your primary has let you down, in which case shouldn't every shot be taken carefully aimed to ensure the efficient use of ammunition?
The way the 1911 is designed and the placement of the slide release makes it far faster to use the slide release than to rack the slide. The ergonomics of the 1911 are surprisingly excellent for such an old design. If I could only take one, I'd take my 1911 over the P226. The 1911 is a personal device, something to get to know and intimate with. Feeding it with .45 ACP ball out of magazines loaded with 7 rounds will help ensure it stays up and running. The safety is the only part of the 1911 that needs to be ambi, everything else is very easy to deal with from left or right.
If a person practices enough, starting slow and building their speed gradually it is possible to learn a detailed manual of arms for each firearm and relatively quickly switch between them.