From: none@none.com99   
      
   On 2/21/2025 7:14 AM, Jim Wilkins wrote:   
   > "Leon Fisk"  wrote in message news:vp8001$2ucs0$1@dont-email.me...   
   >   
   > Thought this "Federal 7mm Backcountry" was interesting. Has been in the   
   > recent issues of a couple magazines. Mostly interested in what the case   
   > and powder could do for current ammo, like the .223 and such🤔   
   >   
   > -----------------------------------   
   >   
   > Standard rifle ammo is little different from what Mauser introduced   
   > around 1890.   
   > https://en.wikipedia.org/wiki/7.65%C3%9753mm_Mauser   
   >   
   > Magnums are only slightly newer.   
   > https://en.wikipedia.org/wiki/.375_H%26H_Magnum   
   >   
   > Hatcher's Notebook explains the technology in considerable detail.   
   > https://ia601302.us.archive.org/3/items/Hatchers_Notebook/   
   > Hatchers_Notebook_text.pdf   
   > The text stamped on the case head actually improves the strength through   
   > cold working.   
   >   
   > The yield strength of hard drawn/stamped brass sets current ammo   
   > pressure limits. It's similar to mild steel but more brittle, and is of   
   > course rustproof which matters to the military. Some bolt actions have   
   > been proofed to handle 120,000 PSI or more if the cases could. Stronger   
   > cases can be turned on a lathe for testing but would be unaffordable in   
   > production. Forming the metal cases more or less paced firearm   
   > improvement since they were introduced in 1808. Smokeless powder that   
   > didn't foul the barrel almost immediately permitted modern action and   
   > ammunition design which was substantially perfected before WW1.   
   >   
   >   
      
      
   Slight tangent to the tangent here...   
      
   There may be another issue with more powerful cartridges.  Most steel   
   barrels have a finite peak operational life of a few thousand rounds.   
   They will still contain the bang, but throat erosion, and rifling damage   
   take a toll on accuracy.  For a typical American hunting rifle this may   
   be the lifetime of several generations of hunter.  For a targe,   
   plinking, or combat rifle this can be much less time, because it is used   
   a lot more.  When you add hyper velocity rounds to the mix the life is   
   severely shortened.  I often wondered if that may have been why   
   Remington discontinued the 30-06 accelerator.  I suspect it was just   
   because 223 and 22-250 was cheaper for varmint hunting.   
      
   Yeah, I know 4150 is better than 4140, and chrome lined bores have an   
   impact on barrel life, but generally rifles used with hyper velocity   
   ammunition will experience a much shortened barrel life.   
      
   There are alternatives of course.  A heavier projectile is one.  We have   
   two ways to get a heavier projectile.  Make it longer or increase the   
   diameter.  In the US for private sporting use we are limited to .50   
   caliber.  That means make it longer.  As is well documented a longer   
   bullet requires a faster spin rate.  We saw that in the M16 and AR15   
   class of rifles with longer heavier bullets.   
      
   Side Note:  I'm pretty sure I have mentioned it here before, but my   
   father in law, Robert F Perry, was the engineer in charge of building   
   the M16 production line at General Motors Hydramatic.  He claimed he was   
   the one who solved the stability issue with the M16-A1 shooting longer   
   heavier bullets by increasing the rifling rate and spinning the bullet   
   faster.   
      
   In any case I'm moderately arm chair familiar with the issues.   
      
   The whole thing about 556/M16 being designed to tumble and maximize   
   damage was a myth.  It was a problem solved by a faster rifling rate for   
   the heavier bullets.   
      
   Reductio Ad Absurdum:  How fast do we need to spin a 4 inch bullet   
   traveling at Mach 3 in order to stabilize it?  What do we need to slow   
   down barrel burn out if we are pushing it at Mach 6?   
      
   Its all solvable of course, but its going to take some figuring out.   
      
   ~~~~   
      
   What is that?  Looks like an animal was run over repeatedly by a D9 Cat.   
      
   Oh, its the Elk Jim shot with his brand new Mach 6 Ruger American rifle   
   shooting 50 caliber 2000 grain pointed soft point boat tails at Mach 6.4.   
      
      
      
      
      
   --   
   Bob La Londe   
   CNC Molds N Stuff   
      
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