Aggie01
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Post by Aggie01 on Oct 6, 2009 12:33:27 GMT -5
Anybody have reason to believe that transonic turbulence affects heavy handgun bullets?
Reason to believe it doesn't?
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Post by AxeHandle on Oct 6, 2009 13:21:55 GMT -5
I vote "yes"  The ole F Class goal is to stay supersonic to the target just for that reason..... ;D Of course I think that at revolver velocity and range it is most likely a moot point... One confusing bit of info I ran up on back when I had my own personal aerospace engineer... He said that any advantage to be gained with the boat tail shape was virtually nil until you went subsonic....  |
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COR
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Post by COR on Oct 6, 2009 13:39:38 GMT -5
Aggie01, That just makes my "country boy" head hurt. But since you asked I have a follow up... Does this mean I will see the Prandtl–Glauert singularity when I fire each shot? You started it..... |
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Aggie01
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Post by Aggie01 on Oct 6, 2009 13:55:38 GMT -5
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Post by AxeHandle on Oct 6, 2009 14:26:56 GMT -5
Ouch! I feel a pain but it isn't in my head!  Did get my vote in though.... ;D |
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Post by sugarriver on Oct 6, 2009 14:58:45 GMT -5
I recall Carlos Hathcock would "hold off" to compensate for transonic turbulence on the LONG range targets.
Pete
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Post by Mark Terry on Oct 7, 2009 20:40:58 GMT -5
Am I in the right place?
First, (after reading, but not neccesarily understanding Aggie's 'light reading'), I'd presume you'd have to be shooting said heavy projectile at >1,125 feet per second and the shifting of the CP would occur on deceleration through the transonic range. Given that lead is reasonably dense, I'd presume the shift would be slower and dependent on the deceleration rate. If said projectile were fired at considerably higher velocity and stabilized (spinning), I'd expect the rotation would be great enough to counteract the effect of the CP shift through the transonic range.
In other words, I don't have a clue. I will plan to use the description to explain my next observed miss.
I would tend to think it would be impossible to "hold off" to compensate for a tumbling bullet and something between spinning and stablized and tumbling could vary off course in any direction.
You're starting to worry me Aggie.
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Aggie01
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Post by Aggie01 on Oct 7, 2009 20:58:38 GMT -5
I really expected this thread to get more discussion from the experienced handgunners around here. What if I said something bordering on blasphemy, like that EK's 1200 fps 44 special load was needlessly supersonic? Would that get a rise out of folks?  |
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Post by Mark Terry on Oct 8, 2009 9:39:22 GMT -5
Lee,
Can you set up a high tech, egg head section just for Aggie? ;D
Aggie,
My guess is that there are a reasonable number of well educated members with technical backgrounds and experience who could could, if they decided to, understand and work through the technical external ballistics around general sixgunning as we practice it. However, regardless of the results of the computations and calculations, if the holes are too far apart on the target, everyone of us would go back to the more standard trial and error methods.
Too, it's possible that some members do technical / engineering / scientific sort of work everyday and sixgunning is an escape from the technicalities.
If it shoots good, should we worry about the details?
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papa
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Post by papa on Oct 8, 2009 13:20:23 GMT -5
I subscribe to the old military acronym KISS ;D ;D ;D That's why my weapons and camera are so much alike. Point and Shoot!! Papa but I did vote... |
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Post by Markbo on Oct 8, 2009 14:33:36 GMT -5
OK, I'll throw in... I hope the ballisticians/scientists will add some more first hand experience, because I am just going to offer a test.
I know about this phenomenon mostly from shooting .22's. It is no secret that competition .22 shooting is done with match/subsonic ammo. Why? Because it's cheaper?
Not hardly! Because it doesn't go through the sub sonic barrier. With those tiny/light pills it can make a heckuva difference in accuracy - where accuracy is measured by the .00xx".
There are those that argue that 1000/inch is 'statistically insignificant' in center fire handgun shooting where the bullseye is about 2 1/2" (5c actually). The scoring is done by adding the numbers, not measuring the group.
I am sure Axehandle and some others that have competed can tell us if there are CF handgun sports where total group size is the standard - I am not aware of any.
So... that leaves us with real world results. Let's say shooting handguns at long range at game. I know of no one that recommends shooting subsonic hunting loads because of the sound barrier interference factor because besides accuracy, everyone wants velocity, right?
One sure and easy way to test this is to take ONE gun and ONE bullet and find two very accurate loads - one subsonic and the other supersonic and shoot them both at short range (say 25yds) and then at long range (say 100yds) on as calm a day as possible to avoid the wind being an uncontrollable variable.
If done on the same day and with optics to take just one more variable out of the equation, you could then determine if THAT bullet in THAT gun was more accurate at longer range with a sub or supersonic load.
Done with a revolver adds one more variable though obviously there are revolvers that can actually put every bullet in virtually the same spot at 25yds. Done with proper pistol bullets in a pistol caliber.
The .32 S&W Long dominates the 25m shooting game with a BC of 0.44 for a 95gr lead bullet but it's velocity is much too slow for consideration. a 158gr .357 bullet has a BC of 1.21. a 240gr .44 - .151 and a 250gr .45 - .117. These are rough numbers of course but it would seem on paper, the .44 bullet would be the best standard. In fact the 300gr Speer JSP's BC is 0.213 that might be an even better choice.
So all it would take is a handgun that can fire a bullet very accurately with a load that is 1125fps (depending on altitude of course) and a load that will be supersonic at the muzzle, but subsonic at 100yds. I don't have a program here to give you an exact number but that would mean a muzzle velocity for the 300gr bullet in the neighborhood of 1300fps, again altitude/pressure dependent. Easily doable.
The groups do not have to be identical at 25yds... simply accurate and close enough that you can measure a standard delta for extrapolating out to 100yds.
So, who has the expertise, hardware and components to pull off this test?
Why Axehandle of course!
Think of the science, man! It has to be done!
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Post by Mark Terry on Oct 8, 2009 16:26:39 GMT -5
I second the motion.
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Post by the priest on Oct 8, 2009 19:48:19 GMT -5
I believe it's accepted that turbulence comes from the TRANSITION from supersonic to subsonic. So if you want to be most accurate,.....be above or below that margin all the way to the target. If you're crossing that velocity the bullet might stabilize after transition,....it might not.
Will it be effected, yes. Will your bullet be able to recover before it hits the target is the real question IMHO.
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Post by maxcactus on Oct 8, 2009 20:09:55 GMT -5
So, who has the expertise, hardware and components to pull off this test? Why Axehandle of course! Think of the science, man! It has to be done! If Axe is unable to help due to too many custom-irons in the fire, I would say a gentleman who could and likely would help us in this quest would be VarmintAl. I don't mean to volunteer him, but he is extraordinarily knowledgeable on such subjects, being a retired engineer and consummate accuracy experimenter & amateur ballistician. I do a lot of hobby studying on the subject of ballistics. Al, on the other hand, is the real deal. He's only an hour and a half down the road from my place, too, though I have yet to meet him. I have learned an immense amount of good information from his outstanding site. www.varmintal.com/Fr. Frog's site may also be able to shed some light on the question, though he is a big less technical & analytical in his writings: www.frfrogspad.com/Lee, forgive me and feel free to edit if I'm violating any policy of which I'm unaware. All of the above said, I would say any projectile crossing the transonic threshold experiences some degree of turbulence, the degree of which depends on many of the factors mentioned above (air temperature/density, altitude (again, density related), etc). I would say detecting this disturbance against any other accuracy-affecting factors with a tool like a revolver would be extremely difficult. When our own JT reports on a FAM83 in .41 Mag shooting 1" groups at 100 yds (as does Hamilton Bowen for some of his revos), I can't imagine we would be able to separate out how much of the inaccuracy is caused by transonic turbulence vs. any other of the various factors that degrade accuracy. I'm with the majority on this one, but you've given me something fun to ponder over the ballistics books. Max. |
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Post by Markbo on Oct 9, 2009 10:33:45 GMT -5
....If you're crossing that velocity the bullet might stabilize after transition,....it might not.... Exactly why I recommended the hotter load slow down enough to to transition before hitting the target. In fact the starting velocity may be too high as the 100yd velocity is just barely sub-sonic... there may be too little distance to affect it. Perhaps starting at 1200fps would give a better idea - IF the load starting at that velocity is accurate. I don't see too many variables coming into it using optics and a Ronsom Rest or similar base. |
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The ole F Class goal is to stay supersonic to the target just for that reason..... ;D Of course I think that at revolver velocity and range it is most likely a moot point...
