Marty1
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- Feb 3, 2009
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Here I go again… too tired from work to do anything but punch the keys. Hoping though to get out to the gun range tomorrow after work. I re-positioned my scope, so I don’t expect to get much done except to “get on paper”. Anyway...back to the subject matter.
When it comes to accuracy with a modern muzzleloader, we hear some shooters tell us that excessive velocities with certain bullets from magnum charges will yield fliers and poor groupings. Can’t argue with that one. But is it also conceivable that too-slow a velocity can also contribute to inaccuracy as well?
Although a non-competitor, I was once a dedicated centerfire “bench-plinker”. I admired my accurate re-loads which possessed those blistering velocities to 3,700 f.p.s. that my 250 yard, heavy-barreled varminters spit out. Before I ventured back in time to the primitive speed of smokeguns, I had to literally do a 180 and throttle-down my mentality to the reality of using considerably slower velocity bullets. So I again here have gathered my thoughts on muzzleloader velocities as I once satisfied my curiosity by thumbing :study: through scientific research. Oddly enough, surfing the internet lately I found similar articles and interests so I am not alone… at least in principle. Most slow-velocity bullets not only lack sufficient power and punch to harvest big game at a fixed distance, but also experience fluctuations in aerodynamic flight from pressure changes acting on the bullet.
Now for the boring stuff.
Unlike almost every centerfire cartridge out there, muzzleloaders are unique in that they venture into the realm of ‘transonic” speed. What is transonic speed? In the simplest form transonic speed covers the velocities between 0.8 Mach and 1.2 Mach. Since Mach speed is equal to 1,116 f.p.s., transonic speed is somewhere between 893 f.p.s. and 1,340 f.p.s. (absent other variables of course). Without getting into the origin and physics of why they classify something as “Mach” speed, transonic speed was essentially an offspring term coined out of necessity in defining one facet of it. Going back to the 1940’s when aircraft speed and aerodynamics were still in their infancy, aircraft designers from such builders as the Lockheed Aircraft Corporation were concerned with the physics of pushing aircrafts beyond 0.7 Mach (533 m.p.h. or 781 f.p.s.). [ If you care to learn more about it (but trust me…you don’t want to know), check-out think-tanks like Newton on his laws of motion, or physicist Theodore Von Karman who had written on the principles of aerodynamics/astronautics.]. During the 1940’s there seemed to be either theoretical aircraft stability issues on paper, or actual problems such as trim changes, maneuverability and unwanted tail vibration associated with moving through air at speeds above 0.7 Mach. That said, we can still theorize today on the phenomenon of unsteady free flight aerodynamics for the primitive muzzleloader projectile coping with transonic speeds. What’s interesting is that sophisticated drag coefficient tests have shown that even very low drag(VLD) centerfires bullets (like a pointed spitzer boat tail) will reach their maximum drag coefficient at a mere and convenient Mach 1.2 (1,340 f.p.s.)…beyond that speed the drag coefficient actually begins to “decline”, even though the bullet is traveling faster. So with the high speed of centerfires, it would appear that the velocity associated with the maximum drag coefficent may never be seen at typical hunting distances. But given the typical velocity range that muzzleloaders function under, it seems that lurking within that troublesome, upper transonic speed of 1,340 f.p.s. is something we must simply work around. Enough said. :scratch: So where does that leave us?
Ever wonder why some of your smoke-loads group well at 50-75 yards, but then spread out-of-control beyond 100 yards… when in theory they should only be dropping in elevation? Is it possible that your velocity for that load at 75 yards is falling into the transonic zone? Unless you have a chronograph or a reliable ballistics table, I guess you’ll probably never know.
So at this point you can either delete and dismiss this post as pure speculation, or make sure your terminal velocity at your maximum hunting range for game remains above 1,340 f.p.s…just to be on the safe side.
When it comes to accuracy with a modern muzzleloader, we hear some shooters tell us that excessive velocities with certain bullets from magnum charges will yield fliers and poor groupings. Can’t argue with that one. But is it also conceivable that too-slow a velocity can also contribute to inaccuracy as well?
Although a non-competitor, I was once a dedicated centerfire “bench-plinker”. I admired my accurate re-loads which possessed those blistering velocities to 3,700 f.p.s. that my 250 yard, heavy-barreled varminters spit out. Before I ventured back in time to the primitive speed of smokeguns, I had to literally do a 180 and throttle-down my mentality to the reality of using considerably slower velocity bullets. So I again here have gathered my thoughts on muzzleloader velocities as I once satisfied my curiosity by thumbing :study: through scientific research. Oddly enough, surfing the internet lately I found similar articles and interests so I am not alone… at least in principle. Most slow-velocity bullets not only lack sufficient power and punch to harvest big game at a fixed distance, but also experience fluctuations in aerodynamic flight from pressure changes acting on the bullet.
Now for the boring stuff.
Unlike almost every centerfire cartridge out there, muzzleloaders are unique in that they venture into the realm of ‘transonic” speed. What is transonic speed? In the simplest form transonic speed covers the velocities between 0.8 Mach and 1.2 Mach. Since Mach speed is equal to 1,116 f.p.s., transonic speed is somewhere between 893 f.p.s. and 1,340 f.p.s. (absent other variables of course). Without getting into the origin and physics of why they classify something as “Mach” speed, transonic speed was essentially an offspring term coined out of necessity in defining one facet of it. Going back to the 1940’s when aircraft speed and aerodynamics were still in their infancy, aircraft designers from such builders as the Lockheed Aircraft Corporation were concerned with the physics of pushing aircrafts beyond 0.7 Mach (533 m.p.h. or 781 f.p.s.). [ If you care to learn more about it (but trust me…you don’t want to know), check-out think-tanks like Newton on his laws of motion, or physicist Theodore Von Karman who had written on the principles of aerodynamics/astronautics.]. During the 1940’s there seemed to be either theoretical aircraft stability issues on paper, or actual problems such as trim changes, maneuverability and unwanted tail vibration associated with moving through air at speeds above 0.7 Mach. That said, we can still theorize today on the phenomenon of unsteady free flight aerodynamics for the primitive muzzleloader projectile coping with transonic speeds. What’s interesting is that sophisticated drag coefficient tests have shown that even very low drag(VLD) centerfires bullets (like a pointed spitzer boat tail) will reach their maximum drag coefficient at a mere and convenient Mach 1.2 (1,340 f.p.s.)…beyond that speed the drag coefficient actually begins to “decline”, even though the bullet is traveling faster. So with the high speed of centerfires, it would appear that the velocity associated with the maximum drag coefficent may never be seen at typical hunting distances. But given the typical velocity range that muzzleloaders function under, it seems that lurking within that troublesome, upper transonic speed of 1,340 f.p.s. is something we must simply work around. Enough said. :scratch: So where does that leave us?
Ever wonder why some of your smoke-loads group well at 50-75 yards, but then spread out-of-control beyond 100 yards… when in theory they should only be dropping in elevation? Is it possible that your velocity for that load at 75 yards is falling into the transonic zone? Unless you have a chronograph or a reliable ballistics table, I guess you’ll probably never know.
So at this point you can either delete and dismiss this post as pure speculation, or make sure your terminal velocity at your maximum hunting range for game remains above 1,340 f.p.s…just to be on the safe side.
