THE DREADED TRANS-SONIC REGION UNMASKED

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Last Post 15 February 2020

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joeb33050 posted this 28 January 2020

There is a popular notion that if the bullet passes through the TRANS-SONIC region; then accuracy suffers. This notion is accompanied by mention of scientific-sounding contentions, but little or no data. Fortunately, data can be rooted out and examined, if the rooter has any interest in fact over popular drivel.

We need enough data to convince, data that shows whether or not accuracy is diminished by bullets passing through TRANS-SONIC world.

We need data on accuracy of a lotta bullets going through TSR, and other bullets NOT going through TSR.

We got it. Rimfire Central, a forum with lotsa experimenters, has a lotta data about 50 shot groups, at 200 yards, with rimfire bullets.

https://www.rimfirecentral.coms/showthread.php?t=1129343

Some 22lr cartridges send the bullet of at speeds less than the speed of sound, about 1125 fps. Others send the bullet of at mv greater than 1125 fps, and, accuracy of these through-the-TSR must be affected-for any 22rf bullet starting above 1125 fps will be below 1125 fps at 200 yards.

No such accuracy effect is seen.

Some examples:

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M3 Mitch posted this 15 February 2020

This is a great thread. It is true that "pat answers" are sometimes thought up, and they can circulate for decades, even centuries, before someone figures out that they are wrong. It is good to have a questioning attitude and to ask for evidence, rather than just accept the "pat answer".

Some years ago I found a .22 bullet just barely embedded, point first, in the roofing material of the old Georgia place where my sister still lives. So that one impacted point first, but for all I know it was tumbling and just landed point first by dumb luck. Anybody got an idea or better yet data on what kind of bullet stays point first along the trajectory, and which ones maintain their initial attitude, flying along with more and more angle of attack as they go?

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Squid Boy posted this 15 February 2020

Ken, that jogged my memory back to Aberdeen and being assigned to dig up artillery shells that had been fired nearly straight up and landed in the impact area about five miles away. They were all point first and about fifteen to twenty feet down. I think we need to keep reexamining some of these givens and I try to remind myself that it took three hundred years for someone to find a mistake in Newton's "The Principia". Thanks, Squid

"Squid Pro Quo"

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Ken Campbell Iowa posted this 14 February 2020

this has been a fun exercise, and it is always good to take a look at nature ( which doesn't care if we look or not ... sigh ... ) ... but ...

i suppose that somewhere in the library of congress there is a massive amount of observational data on the flight of bullets ... probably first look under * Artillery * ..

... and since bullets in air actually fly .... there must be some unbalanced force working on them somewhere ... maybe it varies as the shock wave changes in that dreaded transition ...

oh, and i note that submarines don't have a razor-sharp nose, they look more like a whale ... or a 22 rf. bullet ...

just some thoughts ... ken

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joeb33050 posted this 14 February 2020

I expected to be challenged about Greenhill and it is true about weight not being part of the equation but velocity is considered with the factor of 150 used in the original. I also believe that the original formula was calculated on the basis of a bullet having a specific gravity of 10.9. I noted the weights only to indicate which bullet length belonged with what weight. That and I didn't use Greenhill at all but Bowman's equation which I think is more accurate being refined by using velocity. I usually check it against Miller's that I think is even more accurate and somewhat more forgiving.

I couldn't view the video because it was asking me to sign in to YouTube and I don't have a sign in. The still photos of the sonic wave show it moving back along the bullet and past what would be the balance point. However, my question is where does the force come from that is supposed to upset the bullet? The wave appears to be the same on both sides and if the pressures acting on opposite sides are equal than there is no net force applied. I suppose turbulence at the rear of the bullet could possibly steer it off course or cause it to wobble but I also think if it is spinning fast enough at this point than gyro-stabilization would prevent the movement. I am just trying to make a point that we should not stop testing these theories either in our heads or on the range.

The remarkably consistent explanation of big -delta accuracy decrease by the disciples-sans data-reminds me of stomach ulcer/stress + spicy food explanation for a century, until Australians looked, and found the bacteria. Sometimes ya gotta go over to the window and look, to see if its raining.

I still appreciate everyone that contributed an opinion or data to this thread. If nothing else, it made me think. Thanks, Squid Boy

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Squid Boy posted this 14 February 2020

I expected to be challenged about Greenhill and it is true about weight not being part of the equation but velocity is considered with the factor of 150 used in the original. I also believe that the original formula was calculated on the basis of a bullet having a specific gravity of 10.9. I noted the weights only to indicate which bullet length belonged with what weight. That and I didn't use Greenhill at all but Bowman's equation which I think is more accurate being refined by using velocity. I usually check it against Miller's that I think is even more accurate and somewhat more forgiving.

I couldn't view the video because it was asking me to sign in to YouTube and I don't have a sign in. The still photos of the sonic wave show it moving back along the bullet and past what would be the balance point. However, my question is where does the force come from that is supposed to upset the bullet? The wave appears to be the same on both sides and if the pressures acting on opposite sides are equal than there is no net force applied. I suppose turbulence at the rear of the bullet could possibly steer it off course or cause it to wobble but I also think if it is spinning fast enough at this point than gyro-stabilization would prevent the movement. I am just trying to make a point that we should not stop testing these theories either in our heads or on the range.

I still appreciate everyone that contributed an opinion or data to this thread. If nothing else, it made me think. Thanks, Squid Boy

"Squid Pro Quo"

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Larry Gibson posted this 13 February 2020

"THERE IS NO = NONE DATA, THAT I CAN FIND, SHOWING THAT THERE IS destabilization when going the the sonic to sub-sonic transition."

joe

Simply because you can not find "data" on a subject does not mean it does not exist. There is a wealth of knowledge not contained in EXCEL spreadsheets on the subject. You seemingly want to make a blanket statement of fact based on tests with 22LR at just 100 yards. Your results may apply to the 22LR out to 100 yards but it is in no way "proof" that there is not destabilization of the bullet from stabilized to dynamically stabilized or even totally unstable with other bullets or even with the 22LR at longer range [some do shoot 22LR at longer ranges].

Since you question the veracity of several who have posted actual experience with bullet instability during transitioning from Sonic to sub-sonic, I suggest, for a start, if you can't find the information on Google, that you refer to pages 152 to 160, Transonic Effect on Bullet Stability, in Brian Litz's book Applied Ballistics For Long Range Shooting. Unfortunately the data (there's lots there) is not in EXCEL format but it's relatively easy to understand. You can also find an abundance of discussions with data in most every treatise on the subject.

As to your question; "HOW COULD WE CONFUSE THE TWO?" in your recent post you listed numerous examples of your 22-250 going from "bullet stuck in barrel" to "bullet tipping" to "no tipping". Those example just demonstrate the velocity/RMP level needed to obtain bullet stability. One might suppose some of the tests the bullets exhibiting "tipping" were in the transonic area a large percentage of the distance from muzzle to target and thus was the reason for the instability. However, I would suggest the bullets were on the minimal edge of stability (dynamic stability) if at all and the transition area further buffeted them into instability. The first would mean simply the entire series of tests is meaningless to your hypothesis and there fore the two were "confused". The second would mean you've ample proof your hypothesis is incorrect.

A quick Google search of; bullet instability in the transonic region reveled the following sites. You might read/look at them for a better understanding.

www.accurateshooter.com/ballistics/transonic-effects-on-bullet-stability-bc/

en.wikipedia.org/wiki/External_ballistics

precisionrifleblog.com/2018/09/17/extreme-long-range-tips-ballistics-time-of-flight/

LMG

Concealment is not cover.........

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joeb33050 posted this 13 February 2020

I think that is a great test and i appreciate the data but I am not sure if it shows us anything about the dreaded trans-sonic. It absolutely shows the effect of bullet length / twist rate / velocity on bullet stability but after thinking about it a while don't know if it clears up anything. I measured some 224 bullets I had in the same weights and did the Greenhill for them. The 53 grain was .715" long and the GH said 1:7.7 @ 1000 and 10.7 @ 1900 fps.

GREENHILL CALCULATES MINIMUM TWIST WITH NO VELOCITY OR WEIGHT ENTRY.

A .224" DIA BULLET .715" LONG REQUIRES A MINIMUM TWIST OF 10.526"-NO VELOCITY OR WEIGHT INVOLVED IN THE GREENHILL CALCULATION.

A .224" DIA BULLET .985" REQUIRES A MINIMUM TWIST OF 7.641"-NO VELOCITY OR WEIGHT INVOLVED IN THE GREENHILL CALCULATION.

The 68 grain is .985" long and wanted 1:5.6 @ 1000 and 1:7.8 @ 1900 fps. I don't know if we have the same bullets but they shouldn't be too far off. If my math is correct there is little wonder why you recorded tipping.

I think it brings us back to high velocity / high spin and if the spin diminishes enough that stability is compromised as the bullet goes trans-sonic. It would seem to me that if the bullet is spinning fast enough to be stable at trans-sonic speed it will not be upset by the transit.

THAT'S THE QUESTION, STABILITY FAILURE OR TRANS-SONIC VECTOR DELTA OTHER THAN SPEED.

Maybe I am over thinking this? Thanks, Squid Boy

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joeb33050 posted this 13 February 2020

Let us not confuse the adverse affect of bullets not attaining stability on launch with the adverse affect on a stale bullet going from sonic to sub-sonic.

HOW COULD WE CONFUSE THE TWO?

Also let us remember that some inaccuracy during that transition [sonic to sub-sonic] is caused simply by some bullets being buffeted (moved) around a bit and not destabilized. They may be buffeted around and are still stable flying point forward and not "tipping".

HOW DO WE KNOW IF OR WHEN BUFFETING OCCURS?

Bullets with their center of gravity, center of form and center of pressure (flat based blunt RN'd) are less prone to destabilization when going the the sonic to sub-sonic transition.

LET US NOT CONFUSE THE USE OF center of gravity, center of form and center of pressure IN ONE SENTENCE WITH DATA OR PROOF OR A STRONG SUGGESTION SHOWING THAT flat based blunt RN'd are less prone to destabilization when going the the sonic to sub-sonic transition. THERE IS NO = NONE DATA, THAT I CAN FIND, SHOWING THAT THERE IS destabilization when going the the sonic to sub-sonic transition.

LMG

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Larry Gibson posted this 13 February 2020

Let us not confuse the adverse affect of bullets not attaining stability on launch with the adverse affect on a stale bullet going from sonic to sub-sonic.

Also let us remember that some inaccuracy during that transition [sonic to sub-sonic] is caused simply by some bullets being buffeted (moved) around a bit and not destabilized. They may be buffeted around and are still stable flying point forward and not "tipping". Bullets with their center of gravity, center of form and center of pressure (flat based blunt RN'd) are less prone to destabilization when going the the sonic to sub-sonic transition.

LMG

Concealment is not cover.........

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Squid Boy posted this 13 February 2020

I think that is a great test and i appreciate the data but I am not sure if it shows us anything about the dreaded trans-sonic. It absolutely shows the effect of bullet length / twist rate / velocity on bullet stability but after thinking about it a while don't know if it clears up anything. I measured some 224 bullets I had in the same weights and did the Greenhill for them. The 53 grain was .715" long and the GH said 1:7.7 @ 1000 and 10.7 @ 1900 fps. The 68 grain is .985" long and wanted 1:5.6 @ 1000 and 1:7.8 @ 1900 fps. I don't know if we have the same bullets but they shouldn't be too far off. If my math is correct there is little wonder why you recorded tipping.

I think it brings us back to high velocity / high spin and if the spin diminishes enough that stability is compromised as the bullet goes trans-sonic. It would seem to me that if the bullet is spinning fast enough to be stable at trans-sonic speed it will not be upset by the transit. Maybe I am over thinking this? Thanks, Squid Boy

"Squid Pro Quo"

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joeb33050 posted this 12 February 2020

There are two kinds of tests that I’d like to see done, with longer centerfire bullets.

First is a test showing accuracy both with and without the bullets going trans-sonic, but with both stable, no tipping or keyholing. Like my rimfire experiments.

Second is a test showing accuracy both with and without the bullets becoming unstable, but with neither going trans sonic.

I’m thinking 22 Hornet, 16” twist, at the long bullet threshold and with short bullets.

Below find the results of THE JACKETED BULLET TEST, for all examples showing instability. All 5-shot 100-yard tests.

--------------------------------------------------

22-250, M11 BARREL, 12” TWIST, 53 GR BULLET, 3.0 TITEGROUP, FIRST BULLET STUCK IN BARREL

22-250, M11 BARREL, 12” TWIST, 53 GR BULLET, 3.5 TITEGROUP, 934 FPS, NO TIPPING, 4.125” GRP AVG.

22-250, M11 BARREL, 12” TWIST, 53 GR BULLET, 8.5 TITEGROUP, 1989 FPS, NO TIPPING, .975” GRP AVG.

--------------------------------------------------

22-250, SHILEN BARREL, 9” TWIST, 68 GR BULLET, 5.5 TITEGROUP, 1342 FPS, BULLET SIDEWAYS

22-250, SHILEN BARREL, 9” TWIST, 68 GR BULLET, 6.0 TITEGROUP, 1442 FPS, 4 OF 5 IN 1.9”, 5^TH?

22-250, SHILEN BARREL, 9” TWIST, 68 GR BULLET, 7.5 TITEGROUP, 1715 FPS, MOST TIPPING, .9” GRP

22-250, SHILEN BARREL, 9” TWIST, 68 GR BULLET, 8.5 TITEGROUP, 1875 FPS, FEW SLIGHT TIPPING, .9” GRP

--------------------------------------------------

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 5.0 TITEGROUP, 1138 FPS, BULLETS SIDEWAYS

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 5.5 TITEGROUP, 1243 FPS, TIPPING, 1.6” GRP

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 6.0 TITEGROUP, 1345 FPS, TIPPING, 1.5” GRP

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 6.5 TITEGROUP, 1403 FPS, TIPPING, 1.1” GRP

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 7.0 TITEGROUP, 1403 FPS, SLIGHT TIPPING, 1.05” GRP

22-250, 223 22-250 BARREL, 9” TWIST, 68 GR BULLET, 8.5 TITEGROUP, 1750 FPS, SLIGHT TIPPING, .850” GRP

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223, STEVENS BARREL, 9” TWIST, 68 GR BULLET, 4.O TITEGROUP, 1025 FPS, WILD SHOTS

223, STEVENS BARREL, 9” TWIST, 68 GR BULLET, 4.5 TITEGROUP, 1188 FPS, MOST SIDEWAYS, 1.367” GRP

223, STEVENS BARREL, 9” TWIST, 68 GR BULLET, 5.0 TITEGROUP, 1349 FPS, TIPPING, 1.117” GRP

223, STEVENS BARREL, 9” TWIST, 68 GR BULLET, 5.5 TITEGROUP, 1491 FPS, TIPPING, 1.483” GRP

223, STEVENS BARREL, 9” TWIST, 68 GR BULLET, 6.0 TITEGROUP, 1632 FPS, TIPPING A LITTLE, .925” GRP

TIPPING A LITTLE THROUGH 7.5 GR TITEGROUP, 1923 FPS

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223, STEVENS BARREL, 9” TWIST, 53 GR BULLET, 2.5 TITEGROUP, 913 FPS, TIPPING A LITTLE, 3^RD SHOT STUCK IN BARREL

223, STEVENS BARREL, 9” TWIST, 53 GR BULLET, 3.0 TITEGROUP, 1220 FPS, NO TIPPING, 1.15” GRP

NO TIPPING AT HIGHER VELOCITIES

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Squid Boy posted this 12 February 2020

I shoot a 5.6x61 vom Hofe SE with 90 grain bullets but can't slow them down enough to test at the range I have available and see what happens. The barrel has a 7-1/2 twist and is very accurate to 200 that I have available but would be interesting to see what happens out at 1000 yards and beyond. What comes to mind here is that our fighter planes routinely fly at well above the speed of sound and then return through trans-sonic to land and I never hear anything about loss of control due to that. I know that with earlier jets people were more concerned in going super-sonic than coming back. Also, could it be that we are talking about instances where the bullet is only marginally stable to begin with. Like a very long bullet in a slower than needed twist? Wish I could test this myself. Squid Boy

"Squid Pro Quo"

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Ken Campbell Iowa posted this 11 February 2020

...looks like ..... short blunt bullet are not affected measurably by those mysterious forces of the transition danger zone.

is there a simple test that we old shooters who wear out walking more than a hunnert yards to the target and back can try ?

? need ? to test with sharp bullet reasonably long ... right away it would seem if we slow down a long pointy bullet to 1350... so it would go crazy at 100 yards ... it would be too long for the spin rate anyway... joeb has some interesting data on exactly this ...

so would short pointy bullets show this disastrous symptom ? ... how about 35 gr. 224 hornet bullets ... or 110 gr 30 cal ? ... should be able to shoot at 1350 and go bananas at 100 -200m ?

if that works, then we will still wonder if the spin itself just slows down, and the tip starts walking around in an arc ...

*********

i try to visualize what could happen, and my best delusion is that the shock wave at high speeds moves on the bullet as the bullet slows down ... apparently in an a random manner.

i had thought that johna with his long pointy cast bullets in 22 cal could test for this .. but it would take about a 4 twist to stabilize those pencil bullets at 1350 fps muzzle ... so those would have to be tested at 600 yards or so ... not the simple easy test we need.

comeon, guys .... simple but effective test for sound-barrier effects on pointy bullets.

ken

oh, how about 224107 pointy bullets reloaded into joeb's variable 22RF gas gun ? ...

ken

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Bud Hyett posted this 11 February 2020

Shooting at the Marston Municipal Ballistics Laboratory Range with Ed Doonan many years ago, we observed a slight disruption in the trajectory on the way to 200 yards. The Sun was directly behind the benches and we could track the bullet on its way to 200 yards. There wa a slight aberrance in the trajectory at about 175 yards. This was done on a light wind day with wind flags and two people trading rifles and different ammunition.

The end result of many rounds of .22LR Match ammunition was this aberrance in the wake of the bullet occurred, but the occurrence was the same each time and there was no effect on accuracy.

Farm boy from Illinois, living in the magical Pacific Northwest

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joeb33050 posted this 11 February 2020

Today I shot 20 5-shot 50 yard groups with the Winchester 69A and Federal HV Match ammunition. 10 groups with the barrel hole blocked with a cap screw, 10 shots with the valve body and bolt-3/32" hole.

Blocked, mv = 1200 fps, group size = 1.493"

Valve Body, mv = 1069 fps, group size = 1.345"

The blocked bullets managed to slip through the trans-sonic region without becoming wildly inaccurate.

A Student's t test accepted the null hypothesis: Accuracy under the two conditions is equal.

We have a substantial amount of data showing that for 22 rimfire bullets, the DREADED TRANS-SONIC REGION does NOT reduce accuracy/increase group size.

Absent data to support the DREADED TRANS-SONIC REGION diminished accuracy theory, for jacketed bullets,the test data strongly suggests that ALL bullets are unaffected.

Since the myth exists, rimfire ammunition manufacturers do not make match-grade high velocity ammunition; hence there is no hv match ammunition to test. Note that the Federal HV Match ammunition becomes MATCH ammunition through box-labeling.

(Ed's "clear demonstration" is not clear about what it is a demonstration of.)

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Smoke Ratchet posted this 07 February 2020

A clear demonstration is to stand in the pits and pull targets for someone shooting 168-grain M852 at the 800 yard stage of the Palma Trophy Course, to observe full-profile keyholes and 6 foot groups, then change to M118 and repeat the test and note the round holes and reasonable group size.

AMEN !

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Larry Gibson posted this 02 February 2020

'It appears, Larry, that all bullets follow your theoretical explanation, except for those that are tested."

No Joe, it is not my theoretical explanation. What i said was; "Bullet shape, sectional density, BC, the angle of the bullet in relation to direction of flight (some bullets don't nose over at long range), where the transition takes place in the trajectory, etc. are just a few of the variables." You will find those basic facts in every treatise on the subject. I was just pointing out that based on one example [in this case your use of the 22LR] a conclusion based on that one example may not be correct because of the variables involved.

As to "except those that are tested" I did not say anything about your test(s). I pointed out some facts that may be influencing the results is all. Actually, I thought the results of your last test ere interesting and, perhaps, did demonstrate the HV 22LRs were less accurate than the subsonic......a fact that has been known for many, many years by small bore shooters. Could be you've hit upon the reason why?

In your 1st post you referred to the transition from sonic to sub-sonic buffeting and loss of accuracy as a "notion" stating there was "little data" on it. The fact that some bullets, and what their shape generally is, sustain much less buffeting when transitioning from sonic to sub-sonic has been tested extensively by many. It has been studied and discussed and much well tested data has confirmed the problem. A study of ballistics will provide that information. Again, not my thoery but fact.

BTW; I am looking forward to your continued experiments along this line as i do find then interesting.

LMG

Concealment is not cover.........

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45 2.1 posted this 01 February 2020

The desk wizards have blathered for decades that rpm doesn't decay much in range. Lately some have suggested the opposite. Nobody knows how to measure rpm of a bullet zooming through the air. .

Interestingly enough they do Joe. The "Black Powder Cartridge news" carried an article by Mike Venterino about the shot that Billy Dixon made at Adobe Walls when shooting at Indians in the Western period. Two people disagreed that the shot could be made with the period Sharps black powder rifles. Mike got invited to a military installation where the question was put to rest. The military has tracking radar. They tracked the bullet, noting when it was stable then not stable, through several cycles in flight. They also noted trajectory, velocity etc. Truly amazing what our Gov. has to do with. The shot at some 1700 yards was possible at less than 5 degrees barrel inclination..... So Yes, it can be done.

What tests do you suggest?
If you're going to do the tests, then use one of those accurate rifles you have to validate your procedure.........................

What tests have you done, recently?

I do accuracy/stability tests at longer ranges with some very interesting results! You really don't learn much of what goes on at 100 yards.

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Squid Boy posted this 01 February 2020

I am not sure how one would calculate the reduction in speed of rotation relative to the velocity. I assume that drag would slow the speed down quicker than the RPM but that may not be the case at all. I mentioned the video because the one bullet was spinning on its nose for quite a while. I would post the link if anyone is interested. Thanks, Squid Boy

"Squid Pro Quo"

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joeb33050 posted this 01 February 2020

Joe, thanks again for re-posting that target with the printed on data. Helps my old eyes. It seems then if you were to throw out that one flier you would really have two very similar groupings but to make it fair you would also have to toss the peripheral six extra shots from the other group. What would that measure, just for fun? Searching the net does bring up some interesting things. I found a video of guys shooting a pistol into a frozen lake and had the bullets bounce back and stay spinning for more than several seconds on the ice. Apparently the urge to stay spinning is rather strong even after all forward motion is arrested. Thanks again, Squid Boy

I certainly think that 50 shots doesn't give us much information. I plan to shoot another 4 25 shot targets, 2 each.

The desk wizards have blathered for decades that rpm doesn't decay much in range. Lately some have suggested the opposite. Nobody knows how to measure rpm of a bullet zooming through the air. .

THE DREADED TRANS-SONIC REGION UNMASKED

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