60's style NM slide lightening

[OnVacation]

I was doing some late night thinking and looking over some older 1960s NM 1911 with internal slide lightening.  I noticed that the slides had significant cuts on both sides of the rear of the slide, and some lightening on the underside of the top of the slide.  Are these factory cuts, or a gunsmith's handiwork?  Anyone know how they held up?  The work reminds me of how national match AR15s run lead weights and free floated barrels, and only externally resemble an issued rifle.  I'm assuming this was intended to keep the gun looking factory original externally?  

 

pics were found online, not sure who the credit goes to for the image, just a reference for what I'm talking about.  I couldn't find much in the search.

 

[Jim Watson]

That is factory.  

Pre '70 Gold Cups had the slide lightened for reliability with midrange ammo, 185 gr 750 fps.  I don't know of anybody trying to wear one out with hardball like Skeeter Skelton did with the Mk IV S70 GC which does not have lightening cuts.  

So did Commanders, which makes sense in 9mm, but .45?  

My 1970s .45 Commander is cut away as you show at the rear but not in the front.  Hey, a Transitional Model, ooh.

I didn't check the Combat Commander; will the next time I have the safe open. 

My Service Model ACE .22 slide is lightened from the inside, apparently the floating chamber is still not enough to cycle a heavy slide.

 

I have no doubt it was done from the inside for normal appearance.  The flutes, toots, and daylight holes seen on the modern race gun would not have sold in those days.

Edited June 9, 2020 by Jim Watson

[22 shooter]

The slide on my STI 40 is cut this way. Tommy Abernathy  did mine

[Supertrunk]

My 1974 .45 Colt Combat Commander has the same slide cuts, they were factory standard when I bought it new.

 

Hope this helps.