Slide lightening is not a new idea. Colt produced LW Commanders and pre-'70 NMs with lightened slides. They took material out of non-stressed areas of the interior of the slide.
More recently, guns built for certain games have had their slides lightened, sometimes quite radically, by thinning the sides (particularly aft of the breech face), and cutting windows into them (top and sides behind the bushing).
The experience of those building straight blow-back .38 Special 1911s might be useful also. Colt's MkIII (I think it was) NM in ".38 Mid-Range" did away with the locking lugs, if memory serves, for example.
This approach might be a bit more practical than whittling a slide out of a bar of Ti!
PS I have a Star with a locked breech (linked barrel) in .380. Llama swung both ways (blowback/fixed barrel and locked breech/linked barrel) in the '50's.
WJkuleck is correct. I have a Colt National Match mid range that uses the 38 Special cartridge. It is a straight blow back design with no barrel lugs.
The chamber does have concentric rings in it so the fired brass looks a bit strange. I imagine this is to slow the action of the pistol with the brass, when under pressure from firing, grips those rings and then releases as the pressure drops.
I guess you could do the same with a 380 but the result is you'd have to spend a ton of money and you'd still have a 380.