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Author Topic: The Transonic Region  (Read 1052 times)

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Offline AtlLaw

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The Transonic Region
« on: December 01, 2009, 03:58:06 PM »
I read a short piece on this subject in Handloader I think it was.  Never thought about it before I started loading for handguns.

But let me ask:  If having the bullet go from supersonic to subsonic is such an accuracy problem, the speed of sound being 1100 fps +/-, that you should avoid the transonic region, 900 - 1300 fps, it seems to me you are eliminating the most practical velocity range for handguns.   :-\  Not to mention the exact velocity range I was considering for my handy Handi 45/70 load!

I know this is a factor that is considered in loading for Loooooong range rifle shooting, but what about our practical pistol shooting?

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Offline corbanzo

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Re: The Transonic Region
« Reply #1 on: December 01, 2009, 04:15:36 PM »
In practical pistol ranges, you arent going to have enough drop in velocity to make that much of a difference.  You lose 50fps or so at 50 yards?  Not crossing too far over the threshold, and you weren't that far in front of the soundwave in the first place. 

I could see that at super long shots with rapid slowing, the soundwave hitting the bullet could alter its path, but a large bullet at short range which isn't that far in front of the sound wave in the first place, I dont see a difference.  I haven't seen a difference.
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Offline pozoutdoors

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Re: The Transonic Region
« Reply #2 on: December 01, 2009, 04:37:29 PM »
I've never noticed!!! I guess I just shoot!! It might be one of those things like penitration of a bullet on a deer!!! People make a bigger deal out of it than needs to be!!! I live shooting and deer hunting and don't worry about what some people think. And I use what I know works!!! I'll keep riding my harley and not worry about if other people say a goldwing will last longer!!!!
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Offline Savage

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Re: The Transonic Region
« Reply #3 on: December 02, 2009, 05:44:22 AM »
Transonic range huh? Just about all the handgun calibers I shoot are in that range, other than the .45acp. If it has ever been a factor, I'm not smart enough to have noticed. May use the term though to explain some of my unexplainable misses. ;)
Savage
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Offline Steve P

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Re: The Transonic Region
« Reply #4 on: December 02, 2009, 08:59:32 AM »
Most of what I know about this can be written on the head of a pin.  What I do know is this:  With some .22LR ammo my Contender shoots well out to 100 yards.  This is either high velocity or sub-sonic.  Ammo that lands in the middle between these, has a propensity to fly all over at about 75 yards.  So if I am shooting ammo up to about 1000 fps, I am fine.  If I am shooting the stuff that is 1250 or whatever I am fine.  If I am shooting Standard Velocity ammo that drops from sonic to sub-sonic at about 75 yards, it goes all over the place.

Most of my pistol ammunition (not .22LR) is either at or near 900fps or over 1200 fps.  I have very little pistol ammo that lands in between.

That Transonic Region must me part of the Bermuda Triangle..........

Steve :)
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Offline Graybeard

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Re: The Transonic Region
« Reply #5 on: December 02, 2009, 10:20:52 AM »
Richard where de heck do you come up with dis stuff?  ??? Did that come up in a case you were trying lately?  ::) Surely you don't actually read books or magazines where they talk about such esoteric stuff do ya?  :o What were you REALLY smoking when you thunk that one up?  ;D Come on now you can tell us. We're your friends so you can be honest with us.  :-\
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Offline Skunk

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Re: The Transonic Region
« Reply #6 on: December 02, 2009, 10:41:31 AM »
Quote from: Graybeard on December 02, 2009, 10:20:52 AM
What were you REALLY smoking when you thunk that one up?  ;D

Richard, being a person of informed and discriminating taste in all other aspects of life, leads me to believe that it is only the best. ;D

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Offline Lone Star

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Re: The Transonic Region
« Reply #7 on: December 02, 2009, 11:36:33 AM »
This is a real phenomenon, bullets in trans-sonic mode will open groups around that velocity.  I too first saw it shooting SB silhouette 20 years ago, when I used high velocity ammo my groups at 75 yards were larger than those at 100 yards.  Switched to standard velocity ammo and group size was proprotional to the range.  Looking at ballistic charts and chronographing my ammo showed that the high vel stuff was trans-sonic (ca. 1125 fps) at about 75 yards.

A few months ago I was developing a new Hunter's Pistol load at 50 yards, keeping the velocity/recoil low.  Groups at 50 yards were just under 1 moa, but when I tried them at 100 yards the groups were close to 4 moa with off-center bullet points.  Adding another grain of powder shrunk the 100 yard groups nicely.  Again, velocity at 100 yards was around 1150 fps with the original load.  This was not a case of bullet instability, the twist was 10" and the bullet a 110-grain in a .30 Carbine barrel.



.
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Offline MZ5

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Re: The Transonic Region
« Reply #8 on: December 02, 2009, 06:15:58 PM »
As Lone Star says, the phenomenon is real, and can have real effects.  Bullet design has a significant impact on how much the crossover (super- to sub-sonic) affects group size.  To wit, 30-caliber bullets.  Take the 168-grain SMK vs. the 175.  The 168 is a much older design and will tumble when shot in 1000-yard matches from a 308 or 30-06.  The 175 will not.  I don't claim to know the design particulars that make the one unstable when crossing the sound barrier.  I understand it to occur as the pressure wave runs up the bullet from tail to nose.  No specific info on pistol bullets though.  Sorry.
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Offline Savage

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Re: The Transonic Region
« Reply #9 on: December 03, 2009, 02:15:21 AM »
Not discounting the destabilization event as a flying object goes from super to subsonic and back again. I've seen models and high speed film of the event. A lot of research goes into the design of rifle bullets and twist rates to negate as much of the effect as possible. My poor hold and trigger work no doubt contribute more to inaccuracy than a transonic event ever could. I'm no student of physics, and haven't had any major accuracy problems with my handgun bullets that I thought attributable to this phenomenon. I'll just leave it alone and let someone deal with it that has mastered the human elements of shooting. I'm still working on that. Interesting thread though.
Savage
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Offline AtlLaw

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Re: The Transonic Region
« Reply #10 on: December 03, 2009, 10:46:53 AM »
Quote from: Graybeard on December 02, 2009, 10:20:52 AM
Richard where de heck do you come up with dis stuff?

I dunno there Will'um...  :-\  I always been the cure-us type.  I 'member talking to a feller who was a submariner and all I could think of was "how do they keep the water from leakin in around that perry-scope."  He thought that question was kinda strange... made perfect sence to me...  :-[

Quote
What were you REALLY smoking when you thunk that one up?  ;D Come on now you can tell us. We're your friends so you can be honest with us.  :-\

Well, the Chief Investigator left the evidence locker open and ...  :o  wait!  no!  I never said any such a thing!  I'm a respectable member of the community!   :P  ::)
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Richard
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Offline Glanceblamm

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Re: The Transonic Region
« Reply #11 on: December 04, 2009, 01:57:41 AM »
Quote
My poor hold and trigger work no doubt contribute more to inaccuracy than a transonic event ever could

Agreed but we are usually good enough when it really counts.
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