Transonic / subsonic instability

[Brushy]

Does anyone have any idea of how much effect the drop to transonic / subsonic velocities has on group sizes? I recently started pushing my 20" 308 out to 800m and am curious as to how much further I may be able to hit (a steel roe deer in this instance) given the impending drop below the speed of sound at longer distances. Will my round be able to retain any kind of consistency at ranges greater than 800m or are things hopeless below the speed of sound?

 

Opinions please..

[gbal]

Brushy,a good question that more should ask-good news is that the target can be hit,reality orientation is that it gets hit less and less frequently and predictably with distance (as we all know):here are some data-since 'transonic' varies a bit with rifle (specifically velocity and bullet BC mainly) here is a pretty good guide for 30 calibre 168 g bullet MV 2800 fps (168 becomes suspect around 700-800y).Here are the hit % on a 10" steel, fired with good ballistic solutions for most of the important variables (drop,gyroscopic spin etc etc that start to bite at distance)-here accurate distances are as given,two values are given for wind error,1 and 5 mph, as that will happen and is variable,and unknowable shot by shot (hence sighters!!).OK:

 

1mph error 5mph error

400y 100 83

500 100 60

600 99 41

700 90 28

800 72 19

900 54 13

1000 35 8

 

The 1 mph error gives the most direct answer to your basic question..(few club shooters will judge wind

that well)...there is a pretty steep drop off in % hits on a 10" steel beyond 700y...of the order 20% worse each 100yards...from 90% at 700 to just 35% at 1000y.

A more ballistically efficient 300 win mag with 210g @ 2800 would be more like 700y 99%,800 94%,900 83%,1000 68% in line with it's much superior ballistics and longer transonic free flight.

 

Remember this is what happens with a decent sample of shots-at least a hundred.Those who fire two and get hits....well, the above tells you just how flukey that was! A 223 isn't the answer either. :-)

 

The 308 data are increasingly even less confident from about 800 for transonic reasons-so the above % hits from 750y may be optimistic-it's hard to calculate as transonic effect is not precisely knowable in detail-and of course varies a bit with bullet design etc.

This should give you a fair idea of the parameters-remember the first column (better % data) is for accurate ranging,and pretty good wind reading (1% error). A fifty yard range reading error and 5% wind error-stalking reality?? means a drop to 26% hits on 10" target at 500y. At what range is it 100%,surprise ,it's 200y -a traditional stalking maximum. ( hot shots may do better reading wind and range of course,though a 10" target is generous too,for most deer-a 10" square is 4x the area of a 5" one-hits therefor pro rata many fewer...

 

Looks like no real roe at distance-we knew that,but now its mathematically computed and confirmed! (Litz)

 

:-)

gbal

[JSC]

I'd say it very much depends on the bullet design.

 

I had very good results with Berger's Tactical OTM bullet, particularly the .30 175gn TOTM, all through the transonic zone at ranges over 1000yds from a 26" barrel.

 

That bullet was specifically designed to stay stable as it goes subsonic and group sizes were consistently good at all ranges and velocities in my experience.

[tackb]

I can add to JSC's info that the 168 amax doesn't like the transonic zone

[Brushy]

Thanks for the info all - Its very interesting. Does anyone have any experience with how the Berger 155g VLDs (#30408) handle the change?

[Shuggy]

As JSC says, it is heavily dependant on the design of the bullet. The key thing is 'dynamic stability'. In really crude terms, bullets with tangent ogives have greater dynamic stability than those with secant ogives (e.g. VLD designs). Likewise, those with shallower boat tails, or flat bases are more stable than those with really sharp boat tails. A perfect example would be the old 0.303 Mk VII ball, with tangent ogive and a flat base, which would happily remain stable out to 3,000 yards from the Vickers machinegun.

 

If you do a search for some of Laurie Holland's posts on here, you will find a lot of useful information about this subject.

[tisme]

A small extract from Brian Litz on the subject

The biggest variable is altitude, or more specifically air density. Air density has the basic affect of slowing the bullet more or less but it also has an effect on stability. Thin air at high altitude will result in the bullet being more stable than the same bullet (fired from the same rifle) at lower altitude. Point being; a bullet that's transonic stable at 5,000 feet Above Sea Level may tumble at transonic speed at sea level. So if you say 'Bullet X' is transonic stable, you need to give the conditions that it was stable. I recall a thread some time ago where an epic argument formed up with two guys arguing that the 6mm 95 grain VLD was stable in a 1:9" twist. Turns out the guys saying it was stable lived at 4,000 feet ASL and the guy who observed it wasn't was at sea level. Of course if a bullet is transonic stable at sea level it will be so at higher altitudes as well (barring temperature extremes).

[gbal]

....and you can read it in his (Laurie's) Accurate shooter article of Sept 22 2014 "Practical Thoughts about Transonic Stability and Accuracy"......

...quoting Litz too that one major factor is the angle of boat tail-7-9 degrees being optimum,10+ degrees too steep for smooth air flow.Some 168 bullets don't make it (Amax is 12.9;but some do-the Berger 168 VLD and Hybrid are 8.7 and 8.5 respectively.)

Flat base are not now usually used as very long range designs,but may have quite short range advantages-and dominate for example 100/200y accuracy 6PPC target bullets around 68g.

gbal

[brown dog]

 

 

A small extract from Brian Litz on the subject

The biggest variable is altitude, or more specifically air density. Air density has the basic affect of slowing the bullet more or less but it also has an effect on stability. Thin air at high altitude will result in the bullet being more stable than the same bullet (fired from the same rifle) at lower altitude. Point being; a bullet that's transonic stable at 5,000 feet Above Sea Level may tumble at transonic speed at sea level. So if you say 'Bullet X' is transonic stable, you need to give the conditions that it was stable. I recall a thread some time ago where an epic argument formed up with two guys arguing that the 6mm 95 grain VLD was stable in a 1:9" twist. Turns out the guys saying it was stable lived at 4,000 feet ASL and the guy who observed it wasn't was at sea level. Of course if a bullet is transonic stable at sea level it will be so at higher altitudes as well (barring temperature extremes).

 

hmmm....need to be very careful about picking out precisely what Litz actually says there:

 

The primary determinant of Mach is temperature (all the other factors tend to cancel themselves out)....therefore your transonic distance will vary at a fixed altitude as temp varies (and NOT as pressure varies). Eg, say, Bisley (regardless of high or low pressure weather systems) on a cold day, putting together reduced vel and changed Mach, your bullets will go less far before 'transitioning' than on a hot day.

 

And, thus, the primary determinant of the difference between Mach at (his eg) 4000ASL and at SL is actually temp related (lapse rate). It may be the difference between accurately reaching 1000 in the summer, but, failing to do so in the winter.

Within the narrow confines of precisely what he's described, he's right, but in the UK, temperature is your make or break.

 

So note that, although he says 'altitude' a few times, he's not actually talking about pressure (alone) ..and the issue isn't just 'which is most dynamically stable?' but 'what's the speed of sound in today's conditions?' and 'when (distance) will my bullets have decelerated to today's speed of sound?'

[Brushy]

Thanks for your replies all. I will check out Brian Litz article - thanks for the reference. The temperature / altitude influence on the transonic point does make sense so I will have to reserve my longer range shooting for hotter days at high altitude!! Does anyone else have experience with group sizes pre vs post transonic - independent of wind drift etc?

[brown dog]

Thanks for your replies all. I will check out Brian Litz article - thanks for the reference. The temperature / altitude influence on the transonic point does make sense so I will have to reserve my longer range shooting for hotter days at high altitude!!

 

No - temp is the primary determinant NOT NOT NOT altitude

 

 

Does anyone else have experience with group sizes pre vs post transonic - independent of wind drift etc?

 

Yes, with 155 scenars I have personally shot at dusk at 1000; and as the temp dropped from +5, to zero deg C, we went from 'able to group' to bullets going everywhere (like mad woman's sh1t).

 

As others have said, there's no hard rule as to what will and won't transition smoothly. This area is entirely empirical.

[gbal]

As JSC says, it is heavily dependant on the design of the bullet. The key thing is 'dynamic stability'. In really crude terms, bullets with tangent ogives have greater dynamic stability than those with secant ogives (e.g. VLD designs). Likewise, those with shallower boat tails, or flat bases are more stable than those with really sharp boat tails. A perfect example would be the old 0.303 Mk VII ball, with tangent ogive and a flat base, which would happily remain stable out to 3,000 yards from the Vickers machinegun.

If you do a search for some of Laurie Holland's posts on here, you will find a lot of useful information about this subject.

 

Shuggy,do you have an informed reference for the merits of flat base and tangent ogive especially wrt 'transonic' accuracy?

 

Flat base,as I said,can have considerable advantages short range precision (and manufacture-eg 125g 30 cal soft points-short range)-and where transonic complication is simply not a consideration.

 

It seems not to sit very comfortably with Berger's current designs-which are boat tail (with near optimum angle) and secant ogive(s)-in the VLDs,and secant ogives in the hybrids (with tangent closer to brearing surfaces).

 

These designs claim-with B Litz authority-to have less drag,so more velocity (as well as less drift).And cf JCM's comment on the 175g Tactical OTM Berger,with explicit transonic design features.

 

I don't know about the MkVII 303 ball-and what criterion of accuracy was used at 3000m-maybe some dispersal would be tolerable for suppression fire against infantry at such distances?

g

[tisme]

 

No - temp is the primary determinant NOT NOT NOT altitude

 

 

 

As others have said, there's no hard rule as to what will and won't transition smoothly. This area is entirely empirical.

I don't agree that temp is a bigger factor on air density. Air density and air pressure can be changed by temperature and humidity but the most significant change is with altitude.

[brown dog]

I don't agree that temp is a bigger factor on air density. Air density and air pressure can be changed by temperature and humidity but the most significant change is with altitude.

You've misread what I said.

 

It was this:

 

Temp is the biggest determinant of Mach.

 

(Note also my point on altitude, lapse rate and Mach)

 

There's no debate here. What Litz says is right, but you have precisely understand exactly what he actually said in order to understand what he isn't saying.

And, because what I've said is also precisely correct, you need to grasp the interplay between the factors described in both sets of information.

He isn't saying that altitude is the primary determinant of Mach - but I can see how his words could be misread that way. And hence my input

 

Temp is the primary determinant of Mach, and therefore (remembering the interplay with myriad other effects such as bullet vel), temp is the primary determinant of when your bullet will 'go transonic'.

[brown dog]

Probably worth re-reading my earlier post. It's very clear

 

hmmm....need to be very careful about picking out precisely what Litz actually says there:

The primary determinant of Mach is temperature (all the other factors tend to cancel themselves out)....therefore your transonic distance will vary at a fixed altitude as temp varies (and NOT as pressure varies). Eg, say, Bisley (fixed altitude , fixed MV and regardless of high or low pressure weather systems) on a cold day, your bullets will go less far before 'transitioning' than on a hot day.

And, thus, the primary determinant of the difference between Mach at (his eg) 4000ASL and at SL is actually temp related (lapse rate). It may be the difference between accurately reaching 1000 in the summer, but, with the same load and mv, failing to do so in the winter.
Within the narrow confines of precisely what he's described, he's right, but in the UK, temperature is your make or break.

So note that, although he says 'altitude' a few times, he's not actually talking about pressure (alone) ..and the issue isn't just 'which is most dynamically stable?' but 'what's the speed of sound in today's conditions?' and 'when (distance) will my bullets have decelerated to today's speed of sound?'

[gbal]

Yes,read carefully-and remember the central variables are interrelated ( eg as altiude increases,both barometric pressure and temperature decrease...but not at the same rates. Some of the changes might seem counter intuitive-eg humid,sticky air is less dense (see eg Sierra Reloading Manual 3rd ed-essentialy it's because the molecular weight of dry air is greater than that of water)...humidity though is the least of the factors,at around 1% effect.

 

BCs are set/measured (the Standard Metro) as if at sea level,with 29.53 barometric pressure,59 F,and 78% humidity.

 

Change any of these parameters,and you are no longer comparing apples to apples (or the same apples,anyhow!)

 

If you have a clear head,try Dan Lilja's "Altitude,Temperature and Humidity" article.

 

(Here 'clear' means not fatigued,alcohol free,really want to know ,sitting comfortably, and reading carefully). :-)

 

gbal

[tisme]

It's not clear to me. Temp has an effect on bullet speed from the barrel and air density. Once the bullet is in the air the density of that air determines the bullets speed declaration. Mr litz says air density not only slows the bullet but also has a effect on stability . So how does temp have an effect on stability other than effecting air density

 

What am I missing here without reading George's recommended book as I clearly don't have a clear head.

[Laurie]

Thanks for the info all - Its very interesting. Does anyone have any experience with how the Berger 155g VLDs (#30408) handle the change?

 

Many years back when Berger Bullets was actually Berger (ie Walt Berger's outfit before his retirement) and VLDs were pretty strange new beasts and only the US military had access to things like Doppler radar, none of us knew much about what worked well at long ranges, or even at what distances bullets went subsonic. Transonic zones were La-La Land to even dedictated L-R shooters, but the military especially the Americans knew from long experience with machineguns what worked and didn't at 1,000 metres and beyond. (I bet they've forgotten 90% of it too as they've all discounted the value of the standard small-bore cartridge and its weapons systems so much these days!)

 

The US Army back in the days of the .30-06 and the 173gn FMJBT as used in L-R arsenal loaded match ammo did a great deal of work on this. They found that when the bullet dropped to within 100 fps above the speed of sound, ie dropped below 1,225 fps give or take a few fps, both group size and wind effects increased substantially, that was at least by 50% on both measures. By chance I saw a post by Bryan Litz on another forum recently which quoted speed of sound + 100 fps as the key boundary rather than the full nominal transonic band (below 1.2 MACH or 1,350 fps in standard conditions of 59-deg F and 29.92 inches of mercury ambient air temperature and pressure.)

 

Rather closer to home, John Carmichael (still around as the main man in HPS-Target Rifle Limited) then an avid TR and MR competitor did a series of terminal velocity tests on 150/155 gn .308" match bullets back in the 90s including the then new and aparently very promising Berger VLDs. BCs as published by bullet manufacturers were basically rubbish, so John got permission to erect a very large twin metallic coated screen type of chronograph behind the butts on a Bisley target and proceeded to shoot various .30 match bullets at it from various distances, also chronographing the MVs, so one could calculate true BCs. This work exploded all sorts of myths, beliefs, opinions etc. The MR people had believed that with the powders of the day, the old 180gn long-boattail MatchKing was supersonic to way beyond 1,000 yards - it wasn't!

 

On the bullets that the TR shooters used to 1,000 yards in what was still before 155gn became the norm, the early VLDs were found to have a definite ballistic edge in terms of retained speeds until (if my memory isn't misleading me) 800 yards at the usual TR 2,950 fps MV levels but at that distance, the speed gap was reducing and had nearly closed; at 900 yards the higher BC conventional bullets were going marginally faster; at 1,000 the VLDs were now significantly slower.

 

It seems the VLDs of that era performed worse than non VLDs once they went into transonic speeds. I wouldn't like to say if that's still the case today, but suspect that it may well be hence the success of the Berger 155.5gn BT Fullbore (and its little cousin, the 0,224" 80.5gn BT Fullbore), and the 185gn Target BT Juggernaut.

 

What the MR competitors knew because they shot 308 Win to 1,200 yards when today's MVs were simply unachievable and bullets were generally lower BC was that certain Sierra MKs seemed more stable and performed better in the wind than anything else, The old and still around 190 and 200gn models were popular in this role and it's only relatively recently the MR guys and girls have made the move to Sierra and Berger 210s. It may be a function of shorter OALs that makes them more dynamically stable. The military especially in Finland and the USA did a great deal of experimental work on this during the 1920s and early 30s largely because of the long-range sustained fire role of 30 - 8mm cal MGs that developed on the WW1 Western Front. It's no coincidence that the 173gn US M1 bullet design and the famous Lapua D4x series FMJBTs are all quite short bullets by today's VLD standards. Litz says that for true extreme ranges, such a bullet design is more dynamically stable than long VLDs - this has nothing to do with rifling twist rates / bullet spin rates as that is gyroscopic stability which isn't the same thing. So beyond 2,000 yards say the state of the art VLD or Hybrid could well tumble to earth whilst the old 200gn Sierra keeps going, or even the 174gn 303 Mk VII of 1910 which in its MG loadings was found suitable for MG battalion massed fire to around 3,500 yards in WW1. This is all extreme range stuff though and doesn't affect hitting a steel cutout at 1,000. (There's a lot of stuff around including on the Internet about the ultra long-range shoots that used to take place until the early 60s in Scotland using the 303, and yes they were surprisingly accurate if the wind wasn't too strong.)

 

The final point I'd make is to look at what the FTR shooters use today. The 155.5gn Berger BT Fullbore is an optimised tangent design and alongside the 185 Juggernaut is the outstanding .30 L-R match bullet design of this generation. At 30-inch barrel, let's not worry about the pressures MVs, it really performs to 1,100. Beyond there, the 155.5 users found they were at a definite disadvantage to the 185 and the better 210s in the GB FCA 1,200 yard stage at Bisley in the annual Long-Range F-Class meeting.

 

So far as heavier VLDs v tangent / hybrid ogive designs go, you can hardly give some of the VLDs away except to the Match Rifle people who use the VLD form 210 Sierra MK and some of the Bergers happily enough (but the 5-ring = 2-MOA for them and they sometimes trade group sizes for retained speed). I can hardly think of a top FTR competitors who uses the 210gn Berger VLD in his or her 'bad weather load' as they all favour the same weight LRBT model and some prefer the 200 or 215 gn Hybrid.

[brown dog]

It's not clear to me. Temp has an effect on bullet speed from the barrel and air density. Once the bullet is in the air the density of that air determines the bullets speed declaration. Mr litz says air density not only slows the bullet but also has a effect on stability . So how does temp have an effect on stability other than effecting air density

 

What am I missing here without reading George's recommended book as I clearly don't have a clear head.

 

In a question about bullet super/trans/subsonic performance there are two factors -

- One what is the bullet's dynamic stability? and

- Two when might it matter in what I'm doing?

Dynamic stability can be best-guessed but only really derived empirically - and boils down to a yes/no answer to 'will it?'/ 'won't it?' - to which your Litz quote was saying 'it depends'.

Transition to super/trans/subsonic ie 'Will it effect me?' 'When?' 'At what range?' will depend for all practical purposes -for a given round- on air temperature and its relationship with Mach

[tisme]

In a question about bullet super/trans/subsonic performance there are two factors -

- One what is the bullet's dynamic stability? and

- Two when might it matter in what I'm doing?

Dynamic stability can be best-guessed but only really derived empirically - and boils down to a yes/no answer to 'will it?'/ 'won't it?' - to which your Litz quote was saying 'it depends'.

Transition to super/trans/subsonic ie 'Will it effect me?' 'When?' 'At what range?' will depend for all practical purposes -for a given round- on air temperature and its relationship with Mach

Thanks for the reply but I'm asking, why and how does temp and it's relationship with Mach have an effect on super to sub stability

[Shuggy]

Shuggy,do you have an informed reference for the merits of flat base and tangent ogive especially wrt 'transonic' accuracy?

Have a look at 'Understanding Firearm Ballistics' by Robert A Rinker, the subject is covered in there.

 

The way I understand it, the centre of pressure of a supersonic bullet is forward of the centre of gravity. However when a bullet goes through the transonic region, the centre of pressure moves forward, towards the tip of the ogive. If the ogive is longer and more pointy, then the bullet will have a greater moment of inertia about its longitudinal axis. More simply, the longer tip can act as a lever and therefore amplifies any dynamic instability caused by going through the transonic zone. The stability formulas show that shorter and fatter projectiles tend to be more stable.

 

Likewise flat based bullets tend to have greater dynamic stability because they will be shorter for a given weight than boat tail bullets, which will also reduce the moment of inertia.

 

We have mentioned the 0.303 Mk VII already, but the ultimate example would be Billy Dixon's 50-90 Sharps, launching a dumpy lead flat based bullet at about 1,200 fps. These will happily trundle through the transonic zone with minimal loss of dynamic stability and are capable of surprising accuracy at long range.

 

Fantastic info from Laurie and others on this thread (as always!).

[brown dog]

Thanks for the reply but I'm asking, why and how does temp and it's relationship with Mach have an effect on super to sub stability

 

I'm afraid I'm giving up. Please re-read my last post.

[brown dog]

 

I'm afraid I'm giving up. Please re-read my last post.

Just back from a spin with the dog. I've realised there's a conceptual gap behind your question.

 

First up: You have twigged what the word 'sonic' in super-trans-subsonic is referring to?

Second up: You have twigged how the concept of Mach relates the word 'sonic'? and that Mach varies dependent on the characteristics of the medium in question?

 

Litz is saying that a bloke living on top of Ben Nevis may have a different view of which bullet 'transitions well' compared to a bloke who lives by the sea.

 

I'm saying, we all live at around the same alt in UK, so Litz's observation is 'nice to know' but of no practical value to a UK shooter. If a UK shooter, who knows what he's doing, says a bullet doesn't transition well, the same will be true for all of us.

 

What is of value is understanding / appreciating that Mach in the air we breath varies day by day - the primary determinant in calculating 'today's Mach' is air temperature.

 

And because of what the 'sonic' in 'transonic' is referring to (ie your bullet's velocity relationship to today's Mach at this air temp!) changing Mach changes the distance (range) at which your bullet goes transonic: Not only is your bullet travelling more slowly, but the speed of sound is reduced...

which all adds up to your bullets decelerated velocity and today's Mach value meeting (which is when this transonic stuff 'happens') at a different point on the range.

 

Right. I really do give up now

 

If confusion remains, see this: https://en.wikipedia.org/wiki/Speed_of_sound#Mach_number

[tackb]

 

Just back from a spin with the dog. I've realised there's a conceptual gap behind your question.

 

First up: You have twigged what the word 'sonic' in super-trans-subsonic is referring to?

Second up: You have twigged how the concept of Mach relates the word 'sonic'? and that Mach varies dependent on the characteristics of the medium in question?

 

Litz is saying that a bloke living on top of Ben Nevis may have a different view of which bullet 'transitions well' compared to a bloke who lives by the sea.

 

I'm saying, we all live at around the same alt in UK, so Litz's observation is 'nice to know' but of no practical value to a UK shooter. If a UK shooter, who knows what he's doing, says a bullet doesn't transition well, the same will be true for all of us.

 

What is of value is understanding / appreciating that Mach in the air we breath varies day by day - the primary determinant in calculating 'today's Mach' is air temperature.

 

And because of what the 'sonic' in 'transonic' is referring to (ie your bullet's velocity relationship to today's Mach at this air temp!) changing Mach changes the distance (range) at which your bullet goes transonic: Not only is your bullet travelling more slowly, but the speed of sound is reduced....and your bullets velocity and today's Mach value meet (which is when this transonic stuff 'happens') at a different point on the range.

 

Right. I really do give up now

 

If confusion remains, see this: https://en.wikipedia.org/wiki/Speed_of_sound#Mach_number

 

 

wasn't sonic a hedgehog?

[gbal]

OK, a good discussion-maybe we are getting near a workable answer,thanks to Matt's canine spin and conceptual drift gap narrowing.

Hedge(hog) ing absolute theoreticals a bit,for the dog's sake, bullet stability becomes suspect as the bullet's speed through the air (an imperfect gas medium) decreases towards the speed of sound (sonic Mach).In these transonic zones,dynamic stability is reduced (it wobbles) and dispersion increases ( accuracy/precision decreases.)

The speed of sound is not a constant,and varies with the medium through which the sound passes (eg it's faster in water-don't try it). The bullet's velocity is also affected by various factors that change the medium/air characteristics-as Matt says,both speed of sound and bullet velocity are changed by conditions.

Whatever the theoratical calculations,and these are doable-some ballistic apps will do them for you-when experts comment,it ay or not really have much impact in a particular location-thus,humidity is never more than a 1% factor on bullet dispersal-so can be ignored "pragmatically'-ie in hitting a reasonable sized target in UK,ditto altitude variations are too small to be a big issue,except perhaps for ultimate accuracy targeteers,but UK just does not have ranges multi thousand feet apart in altiitude or pressure.

Temperature does have a clearly discernible effect-on both bullet velocity (hot days more velocity,and speed of sound)... and we have enough temperature variation in UK seasons to benefit performance when corrected for-in particular temperature affects where transonic occur-and it varies a bit ,of course.

BUt at some variable with temperature point (aka distance from muzzle) the bullet will have lost enough velocity to become transonic on that day (temperature/speed of sound.)

 

Good doggie! On warm days,then ,the transonic zone may be a bit further from the muzzle,because bullet velocities are up a bit (sonics too,but not equally).

Much empirical evidence comes from Long Range shooters,and Laurie has detailed some of that.The original post asked about more mundane 168s from 20inch barrels (at presumed 'standard' velocities),and the effect oftransonics on accuracy.

Hence my first table-it's not a 'wind table' but a guide as to the relatively carastrophic fall in accuracy(%hits on a 10 inch steel) at various distances (adding velocities might have helped,but these are variable with load/rifle etc (and temperature)...and can be compared elsewhere easlity enough.

The first set are for near ideal conditions,allowing only 1% wind error-the drop off in accuracy around 700yards-or whatever reduced accuracy you tolerate- is a good guide to othe effects...and is consistent with much empirical data-what shooters have noticed (not 1000+ LR shooters,as rheir gear has been designed to extend transonic range (the data for the superior ballistics 300 win mag are suggestive...)

 

Individual experience will vary,but not randomly-F open in Raton in New Mexico in August will not be the same as half way uo some slope in Assynt culling hinds in a scottish winter (actually,the range there won't even raise the question,of course). It's empirical,and can be found out.Whether it actually matters muc,as Matt says,is another question...yes in Raton precision,probably not for the hinds.-,unless it's 'gey cauld" -pseudo gaelic for sub zero.

 

Shuggy,thanks.RE Rinker_ there is little doubt that flat base bullets have advantages for short range-perhaps because it's just easier to manufacture really uniform balanced lightish bullets with that design,avoiding complex tail tapers AND transonic drag considerations simply don't apply at 100/200/300 etc yards.

There is some debate about centre of gravity moving back with 'hollow point's' and so on,though also some disagreement about static and dynamic stability....put at 'walking the cat ' level- a flat base bullet is pretty stable on its base,static,but distinctly dynamically unstable fired flat base first (don't try it-though it has been done)...largely irrelevant anyhow.

As Litz details,we know that boat tail is critical-ie the angle of boat tail.

 

Almost-or all- contemporary Long Range design bullets are boat tail-because it's a quite different ball game at 1000y sort of distance,where drag/transonic etc bite,and ballistic efficiency is important. More complex designs with higher BCs and reduced dispesions pay real dividends.

 

BIlly Dixon is anecdotal-and a single shot (unlike Quigley...in Holywood). Machine gun fire at 3000yards was not 'accurate' in our accepted sense of an aimed shot hitting a specific intended relatively small target,but rather 'rain on a field',which is accurate if the measure is did some grass get wet. Spotting for the Bison guns gives some respect-for the 'whump' into backstop,and the steel bison is hit,but not often enough from 1000y to threaten the species...modern boat tail hot numbers are grouping sub 1/2 moa.

The Juggernauts at 220 (?+g) have some of the perseverance through conditions of the old heavies,but also all the design advantages that Berger Ballisticians can add....must tell us something about the best bet for replicating Billy Dixon's shot,especially if we want more than one shot to hit.

 

I can't recall the recorded temperature that day at Apache Wells either,so sonics are indeterminate :-)

 

OK,walkies ( theoretical-can't see the garden hedgehog-probably dozed off after paragraph one-or modelling hibernation effects,in the coolness of autumn).

 

gbal