Oh...I apologise, I was writing in haste, and, should have thought more before putting the finger to the Keyboard...
But, yes, the Retention Key, or, the Nose of the Slide where it is located...if firing Ammunition which is too powerful for the Arm as-it-is, then, that areas can end up getting some harsh pounding, or, the Slide Nose can crack there by the Key.
But, it is not clear to me just how much more powerful one could go, Ammunition wise, by installing a stouter recvoil Spring, before reachin the limits of that.
I see NO relationship at all (other than the name and a self-loading mechanism) between the blowback, fixed barrel Model M, and the Model of 1911. As rhmc24 points out, the Model of 1911 has roots in the Model 1900 et seq. The progression went through the Model (Contract) 1907, Model 1909 and Model 1910, NOT through the Model M. Bady has a detailed description of the development of the Model of 1911 that will help explain it all.
May be...or yes, they are differing kinds of function if somewhat similar in appearence. I was just noting what appears to be a resemblance, especially between the earlier Model M with it's Barrel Bushing, and, overall lay out of form, of the Slide and Frame...to, the eventual, M1911. Lots more in common there, than to the Rarallel Rule ones.