From: none@none.com99   
      
   On 1/17/2026 12:09 PM, Jim Wilkins wrote:   
   > "Bob La Londe"  wrote in message news:10kgi8h$2o03r$1@dont-email.me...   
   >   
   > I was not aware of a brittleness property, but that may be a function of   
   > treatment.  It is used for multiple firearms actions including for home   
   > builders in the rather brutal 1911 series.  Of course it was the magic   
   > answer to toughness and corrosion resistance for the M16A1 in Vietnam   
   > over previous alloys.   
   > Bob La Londe   
   > ------------------------------------   
   >   
   > I haven't found a clear and not highly technical reference on its   
   > properties for you. One showed fatigue life around 1000 cycles near   
   > yield strength, rapidly increasing below it. Another mentioned that   
   > sanding parallel to the stress with 150 grit paper was as effective as   
   > buffing to remove scratches that could initiate notch cracking. The M16   
   > bolt locks into the barrel extension and doesn't stress the receiver.   
   > Likewise the 1911 barrel locks into grooves in the slide, not the frame.   
   >   
   > The aerospace advice I heard was to look closely at its strengths and   
   > liabilities before designing with it.   
      
   Its true, the M16/AR15/M4 series of rifles is fairly gentle on the lower   
   as are "most" gas impingement recoil systems since the whole of the   
   operating recoil mechanism is in the upper *(not true gas, and not just   
   direct impingement), but delayed blow back is still pretty hard on the   
   structure.  I wasn't saying 7075 could take repeated hammer blows over   
   and over again, but that it could take a "lot" over and over again.   
      
   * the nature of the Armalite mechanism is sometimes debated.   
      
   My goal eventually for an aluminum 1911 frame is to run one with a GSG   
   .22LR slide which changes things again.  The GSG upper is basically   
   direct blow back fully contained in the slide.  Is there any hammering   
   at the end of the stroke. Maybe, but not much force compared to the   
   torquing of 45 ACP.   
      
      
      
   --   
   Bob La Londe   
   CNC Molds N Stuff   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)