Oedipus Wreckx-n-Effect Posted November 3, 2017 Report Share Posted November 3, 2017 6 hours ago, Collimatrix said: Very aerodynamic bullet made of aluminum with a brass jacket to increase moment of inertia. Used early in CETME development. Kraut space magic but made in Spain. I need them for my Spanish jungle carbine. Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted November 3, 2017 Author Report Share Posted November 3, 2017 6 hours ago, Collimatrix said: Very aerodynamic bullet made of aluminum with a brass jacket to increase moment of inertia. Used early in CETME development. Kraut space magic but made in Spain. The CSP-004 bullet in that photo is actually lead-cored with a plastic tip, in a gilding metal jacket (as they all had). Voss, the guy who designed those bullets, was one of the early pioneers of very low drag small arms projectile designs, and his work was on the bleeding edge of the knowledge of supersonic drag characteristics at the time. Of course, a proper aerospace type would say something like "so what? bullets are perfectly radially symmetrical", but that's another thing. The goal was to produce a round that had recoil characteristics similar to 7.92x33, but 1,000 yard range like 7.92x57 or (later) 7.62 NATO. The project was unsuccessful basically due to NATO standardization (which the Spaniards weren't a part of at the time, but decided to buy into anyway). The end result of this research was a unique 7.62 NATO loading (which I still don't have! despite it being rather common by cartridge collecting standards) which (unlike CSP-004 there) fit inside the standard NATO envelope but fired a decidedly non-NATO spec 113gr low drag bullet at about 2,600 ft/s. Compare the projectile shape of these rounds with the M80 Ball in the last image in my post above: This ammunition was actually issued with the CETME Modelo B rifle, and produced for a number of years until phased out in favor of full power 7.62 NATO. I went off memory for this whole post, so it's possible there are some small errors. Effort lol. That_Baka, Oedipus Wreckx-n-Effect and Zyklon 3 Quote Link to comment Share on other sites More sharing options...
Collimatrix Posted November 4, 2017 Report Share Posted November 4, 2017 I just checked Full Circle. Sturgeon's account is basically correct. After WWII, the Soviets and Americans fought over all the German jet engine experts and rocket scientists, and the French got all the German tank and gun experts. For a period in the late 1940s and 1950s all the French tank designs look sort of like panthers and tigers and all of their rifle designs look sort of like STG-45s, and that's why. As soon as these German scientists weren't forced to wear collars and leashes (early 1950s), most of them moved to Spain where they found the Mediterranean climate and oppressive Fascist dictatorship more to their liking. One of these German scientists was a Dr-Ing Gunther Voss, who was extremely well-informed on the then brand-spanking-new science of supersonic fluid dynamics. As you may recall, supersonic fluid dynamics were a big problem during WWII because nobody really knew how they worked. A lot of pilots were lost in dives when their flight controls mysteriously locked up, since the engineers didn't yet understand how localized supersonic flow could cause a loss of elevator effectiveness. So, prior to some time in the 1950s, bullets were basically designed by trial and error. Gunther Voss was one of the first to scientifically design a bullet for maximum supersonic efficiency. He developed four super-skinny, lightweight, high-efficiency bullets for CETME from the early to late 1950s. They were: CA-001, 8mm 108 grain bullet with an exposed aluminum core and gilding metal jacket. CAP--01, 8mm, 200 grain bullet with a mostly lead-antimony core, and aluminum tip concealed under gilding metal jacket. CA-002, .30 caliber, basically the same as CA-001, but in .30 cal instead of 8mm. CSP-003, .30 caliber, 112 grains, lead and plastic with fully enclosing copper jacket. CSP-004 isn't in Full Circle, so I'm assuming it's something that Sturgeon made up, just like the form 4473. Belesarius, Priory_of_Sion and Zyklon 3 Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted November 4, 2017 Author Report Share Posted November 4, 2017 9 hours ago, Collimatrix said: So, prior to some time in the 1950s, bullets were basically designed by trial and error. In many cases yes, but people did try to design them mathematically, it's just that their mathematics for that sort of thing sucked ass. S Patrone was designed mathematically, for example, using a Newtonian flow model! Quote Link to comment Share on other sites More sharing options...
Oedipus Wreckx-n-Effect Posted November 4, 2017 Report Share Posted November 4, 2017 3 hours ago, Sturgeon said: In many cases yes, but people did try to design them mathematically, it's just that their mathematics for that sort of thing sucked ass. S Patrone was designed mathematically, for example, using a Newtonian flow model! Probably because they require solving PDEs and solving PDEs is only really feasible with modern computers. Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted November 4, 2017 Author Report Share Posted November 4, 2017 2 hours ago, Oedipus Wreckx-n-Effect said: Probably because they require solving PDEs and solving PDEs is only really feasible with modern computers. You can get there empirically, but until the 1930s-1940s there was really no way to accurately measure a supersonic bullet in flight. So for some time, nobody could prove the Newtonian model was wrong. Quote Link to comment Share on other sites More sharing options...
Xlucine Posted November 4, 2017 Report Share Posted November 4, 2017 They hadn't even figured out how to properly scale wing tunnel data back then (eg, the idea that full scale wings on the P-51 could have laminar flow), so messing up bullet design is understandable (much easier to fit measuring equipment on a plane!) Sturgeon 1 Quote Link to comment Share on other sites More sharing options...
Collimatrix Posted November 4, 2017 Report Share Posted November 4, 2017 3 hours ago, Xlucine said: They hadn't even figured out how to properly scale wing tunnel data back then (eg, the idea that full scale wings on the P-51 could have laminar flow), so messing up bullet design is understandable (much easier to fit measuring equipment on a plane!) I thought the lack of laminar flow on laminar flow wings was an issue of imperfections in the surface finish like rivets, dents and bugs, and not an issue of scaling. Quote Link to comment Share on other sites More sharing options...
Xlucine Posted November 5, 2017 Report Share Posted November 5, 2017 15 hours ago, Collimatrix said: I thought the lack of laminar flow on laminar flow wings was an issue of imperfections in the surface finish like rivets, dents and bugs, and not an issue of scaling. In the absence of any surface defects, the transition from laminar to turbulent flow will occur on the outer edge of the boundary layer and propagate inwards to the surface of the aircraft. My fluid lecturer says this occurs at about Re = 5E5, which for an aircraft at 100m/s (~200 knots), and assuming air density of 1.229 kg/m^3 and dynamic viscosity of 1.73E-5, will occur about 7cm in from the leading edge. This is for sea level which is admittedly not representative of most flight, so using the data here this is how the length of the laminar region varies with altitude It gets up to a bit over a foot at high altitude, but is still well below the P-51 chord length (scaling off a 1:76 model I have lying around, ~1.3m at the tip) Collimatrix 1 Quote Link to comment Share on other sites More sharing options...
Akula_941 Posted December 22, 2017 Report Share Posted December 22, 2017 Two type of Chinese made 7.62x51 round for sniper rifle use Probably M118LR clone made by factory791 Collimatrix, Khand-e and D.E. Watters 2 1 Quote Link to comment Share on other sites More sharing options...
Akula_941 Posted December 22, 2017 Report Share Posted December 22, 2017 The first ever real cut-off of 5.8x42 DVC-12 AP rounds bullet weight 5.47g penetrator is tungsten carbide 3.5g that little BB is made by lead Zyklon, D.E. Watters, Sturgeon and 3 others 3 3 Quote Link to comment Share on other sites More sharing options...
Khand-e Posted December 22, 2017 Report Share Posted December 22, 2017 Recovered Petals and cup from 14.5x114mm APDS. Rare 5.8x39mm rounds, made as a competing round to the 5.8x42mm D.E. Watters, Akula_941, Zyklon and 3 others 6 Quote Link to comment Share on other sites More sharing options...
Xlucine Posted January 21, 2018 Report Share Posted January 21, 2018 On 11/5/2017 at 3:30 PM, Xlucine said: In the absence of any surface defects, the transition from laminar to turbulent flow will occur on the outer edge of the boundary layer and propagate inwards to the surface of the aircraft. My fluid lecturer says this occurs at about Re = 5E5, which for an aircraft at 100m/s (~200 knots), and assuming air density of 1.229 kg/m^3 and dynamic viscosity of 1.73E-5, will occur about 7cm in from the leading edge. This is for sea level which is admittedly not representative of most flight, so using the data here this is how the length of the laminar region varies with altitude It gets up to a bit over a foot at high altitude, but is still well below the P-51 chord length (scaling off a 1:76 model I have lying around, ~1.3m at the tip) So this is bugging me, because there's quite a lot of more recent stuff with people trying to develop laminar flow bodies. It looks like the second year fluid dynamics explanation was too simple, and there is stuff you can do with the pressure gradients and accelerating flow to prevent turbulent transition at reynolds numbers of >1E7, so the P-51 designers might have been onto something Quote Link to comment Share on other sites More sharing options...
Sturgeon Posted February 11, 2018 Author Report Share Posted February 11, 2018 The late Gary Hoffman's collection is going on sale. Quote Link to comment Share on other sites More sharing options...
Belesarius Posted February 11, 2018 Report Share Posted February 11, 2018 3 minutes ago, Sturgeon said: The late Gary Hoffman's collection is going on sale. And Sturgeon decides to check on the market value of kidneys... Oedipus Wreckx-n-Effect and Sturgeon 1 1 Quote Link to comment Share on other sites More sharing options...
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