Unfortunately, there are very real reasons why you will never see an auto with a polymer or titanium slide.
First, the small print on Glock ads will tell you that the strength comparison is pound for pound, which really doesn't mean anything. It does bear on the discussion, though.
The focus of handgun design in auto's is the feeding cycle and the mass of the slide. If the slide is overly lightened, the pistol will not feed or extract reliably.
The kinetic energy from the firing of the bullet is converted into motion of the slide of the pistol. if the slide is too light, this means that the slide moves faster. If the slide moves fast enough, the new round can't move up fast enough from the magazine and feeding will be a problem, as well as extraction.
You might think this would be easy to fix, just beef up springs, but if you are into physics(not too many people are), you can figure out that a moving mass has more energy than a reasonable spring can store.
If the only way to rack the slide was to fire a round, the pistol wouldn't be very popular no matter how light it was.
There are other structural problems, the slide locked to the barrel is what contains the chamber pressure from firing, but basically this covers the main problems involved. Hope this helps.
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With my shield or on it...