balliatic coefficient versus accuracy

[Swarovski1]

At what range do the experts think the bc will take over from pure accuracy,bc is more about windage as I see it, obviously a high bc bullet thats capable of say 0.2 groups will be hard to beat if steered correctly, I recently equalled my 1000yds pb with my 6,5 06 which was done with my 6.5 06 and I was on I think to beat that score with my 308 but I had one detail where some slight breeze must of got up and put me 3 out of the 4 just on the backer in nion the same place next to the fig11, basicly it was perfect conditions, never seen it like that before, not a breath of wind showing on the flags at time of the cof.both of my rifles shoot extremely well, one no better than the other at 100yds,being windless is it a level playing field whatever the calibre,thoughts please

[DaveT]

Not sure I understand the question.

 

I think of BC as 'slipperiness' through the air......velocity retention at range and less wind susceptibility....IE a more efficient bullet as opposed to accuracy per se which is more a function of load and barrel harmonics along with other factors.

 

You could use a high BC bullet but still build an inaccurate round as I see it.

[Swarovski1]

The cartridge has to be very accurate to start with.not exactly sure on my question myself.part of it is if it's perfect windless conditions will it make a level playing field

[gbal]

Rather agree with Dave-the question might need changing-BC/accuracy/precision are sperable but overlap too much and involve 'pure' engineering/dynamics AND human factors interacting-and that is complex indeed-as well as individually (ie person to person) variable...And the mix probably changes quite a bit with distance....

 

It's easier for varminting-eg out to around 350 yards velocity edges BC,but threafter BC kicks in seriously-becauase of wind/error reading for example. (of course,high BC includes better velocity retention).

I don't think there is much real evidence for BC effects on short range accuracy-consider eg that 100 and 200 yard bench rest bullets (and they are the most accurately shot) are typically flat base,which isn't the best for BC,where boat tail designs are better (as well as pointy end ogives ) for longer range bullets.

 

So there is some blurring if the question tries to compare BC (bullet design) with "accuracy"-hitting the intended target. Despite some comments,let me reintroduce Litz distinctions-the concepts are valuable,call the rose by any other name if you will:

Precision is what the rifle and ammo are capable of,in ideal conditions-it is essentially a consistency of grouping determined by the engineering and consistency of rifle and ammo. Accuracy is hitting the target,and is what is added to intrinsic precision by shooter skill,and aids like scope,trigger,rest and shooting skill,including wind reading . On VERY rare occasions,wind reading may be a small component-as in this OP- but normally it's one of the largest error factors,the more so in an intrinsically precise rifle combo.

 

SO.... do cartridges differ in potential-yes,some are intrinsically more likely to be accurate and precise.

(one reason the PPC dominates utterly BR shooting to 200y).

 

Can we ask if BC is more/less important than accuracy.....well no,since both have some shared factors-eg velocity retention,time of flight-which relates to wind error dispersal,etc.

 

BC will matter more as distances increase,but there is no trade off formula against 'accuracy'-(with it's human components) nor against 'precision'(what the rifle//ammo can do under ideal conditions-perfect atmospherics,and no human component errors).

 

It's perfectly possible for two different rifles in different chamberings to be almost indistinguishably the same,and two apparently 'identical' rifles to be detectably different,with a fine enough measure of 'holes on target'".

 

Sorry Neil,if I've misunderstood quite what you were asking-a more precise rifle (and /or more accurate shooter) can outshoot a potentially 'better' BC bullet-and indeed cartridge-when it's shooter is less good.

 

A high BC heavy juggernaut may be less precise,but reduces wind reading error more-for someone who can handle it (the human component) than a more precise bullet (any BC comparatively) which is easier to shoot,but more wind drift....with such mixes,the human component is what swings it-but not every shooter can cope equally with every demand. Rifle rule weight limits just emphasise some of complications-the 'best' (gear) might not be allowed in that competition...!

 

Best results come from optimum precision rifles and ammo with accurate shooters using best aids.

I doubt that it can be quantified into each component. The mix may change with distance/target size too!

gbal

[Swarovski1]

Example then, a 284 shehane using 180gr hybrids verses a 308 winchester using a 155.5gr vld, in perfect conditions say they were rail guns to take out human error, just a case of setting up the aim and squeezing a trigger, which would win

[gbal]

Well now Neil,

 

We do have some decent evidence that Shehanes usually outshoot 308s in 1000y Bench Rest,but that's in 'real world' conditions.

I note you don't specify velocities(and transonic complications maybe) but let's assume 'optimum' for both (that of course begs the BC issue!)

 

However,the superiority of Shehane over 308w is clear enough to at least strongly suggest that in 'ideal' conditions the performances are unlikely to be reversed. The gap might be expected to reduce,perhaps a lot....but I can't see the 308w being consistently the winner.

 

( pedantic point-what is 'winning'-group size,hit% on (very small) target...or...?)

 

You'd need about 20 of each of course to even begin to get a decent sample....we may never get such,

so it remains a rainy day discussion .....

 

g

[Swarovski1]

Yeah maybe george, the shehane is a super accurate perforner apparently but often put to one side when the wind is stronger for a 270/7mm wsm because extra power bucks the wind, me thinks in absalute perfect windless condition theyre would or could be a big upset, like I said bc is mainly about windrift, the range when one beats the other has yet to be determined, I was thinking past 600yds

[gbal]

Yes,Neil,but you pitched the (284) Shehane against a 308w.....

 

The Shehane is not the last word on 1000 yard shooting-and is definitely edged by the magnums,including some 30 calibre magnums on ballistics,as well as the currently fashionable and very able WSMs and RAUMs especially in the 7mms (still 'shootable') which seemjust as 'accurate' too.

It's not a fair test,but as I said,there are many more Shehane sub 1/2 moa groups at 1000y Bench Rest than there are 308w ones,though they occasionally occur. The Shehanes of course are 'bettter' rifles,with -maybe-better wind readers......

 

At 600 yards,the 308w has more chance,well within it's comfort zone; though maybe not as much chance as a 6BR (Dasher) in 'perfect conditions'.The Diggle 600y shoot results might help-though they won't all be in 'perfect conditions',with 'equivalent rifles'...

 

 

 

 

I can't off hand-or bench rested-think of any reason the 308w would come out on top in a 'fair' test-it might be close,but how close is 'close enough' ?

 

I don't know of any decent controlled test,but above is how I'd bet if forced to risk 1$,or even 1£

 

:-)

 

g

[Swarovski1]

All spoke about all comes down to the bc as perfect conditions nearly never happens, we may never know the real result, laurie may have a different view on this being a experienced f class shooter.

[gbal]

OKwe can have some confidence that beyond very shot range,within any one cartridge,a better BC will give some advantage in non ideal conditions and as range increases. In idea, its a matter of gravity effects,and a dialled shooting solution.

 

But we cannot say that a higher BC is always better when comparing across/between two or more different cartridges.It should help,but there are other factors,which may go in the same direction,or not-either increasing or detracting the higher BC advantage. Some are bullet design and manufacture /chamber issues.Those are best considered 'precision' factors (engineering)

 

But other factors are the more unpredictable human factors. All can effect 'accuracy',and are interactional sometimes-essentially not completely seperable/measureable. (think 'recoil reactions-both 'ergonomic' (recovery time) and 'psychological' (flinch)-both vary between shooters.

 

Does it matter-well,we can at best only get general clues,and probabiliies,by looking at actual shooting

(remembering fashions change and influence what is 'on the line' at any time,but fashions tend increasingly to have some empirical base- ie they seem to work better....for now! so they are not fashions pure and complex.

 

gbal

 

ps "Fashion is such a ridiculous idea that we have to change it every year"- Oscar Wilde

 

Shooting has much stronger emirical reasons for change,but not aways perfect ones.

[The Gun Pimp]

The 6mm flat-base custom-made bullet in the 66-68gn range will out-shoot pretty well everything out to 300 yards (when loaded into a small case like the 6PPC) - it certainly holds all the accuracy records out to this distance. The BC however is abysmal.

 

But then again, I doubt that anyone has tried to do the same with a 284 Shehane.

 

In a way, it's a pity we don't try it. The 6PPC benchrest records are of course established in competition - rather than simply turning up to shoot a few groups but, if we did just have a 300yds 'record day' it might produce some interesting results.

 

We did a similar thing at Diggle about 20 years ago - just to get 1000 yard benchrest off the ground in the UK. If I remember, the best 5-shot group was 8.125 inches using a 6.5x55 cartridge.

[gbal]

Vince,I made exactly your point about flat base bullets in 6PPC in the earlier posts on this (I might have added it's another of these pesky interactions-BC moves from unimportant to paramount as distance gets large).

I would imagine most cartridges-including Shehanes have been tried at 100/200 yard Bench rest (and about everything else) especially in the US. What is clear is that only very very rarely does anything other than a PPC (or derivative) succeed,even in a few matches.It's more typical for the top 20 (at least) to be all 6PPCs.

So-on that good evidence-and the occasional report of another contender (which typically fails to catch on) we can be reasonably sure the 6PPC is the best (though there are very occasional exceptional rifles chambered otherwise which do very well indeed in factory class,in UK-Diggle!)

 

But OK, the current hot cartridges for 600 and 1000 Bench Rest are probably not shot extensively at 100/200,or if they are they don't win (deducting calibre size from edge to edge group would favour them,note-even if they did not quite shoot so well).

 

Of course an 'open day' bring it on is a good idea,but is unlikely to prove much-just as the first one you describe didn't-it showed that on that day,that rifle/cartridge and shooter shot best. I daresay 6.5x55 enjoyed some successes,esp in Ack Imp chambering...before being a bit outclassed by others,Shehanes,WSMs and so on...and this will likely continue (sometimes it's also a change in shooting technique too-as 'fast shooting' the 6BR-that leads a new challenge.

 

But these have to be consistent to catch on...shooting has a probabilistic base-a tight one to be sure in the best competitions-but one offs won't displace established successes too readily.

Absolutely fun and interesting to try,of course...and someone has to introduce the 'next best thing',but it has to be earned over competitions/shooters/and time.

Wild cats do sometimes become domesticats,or even remain wild,but prolific.

But it's always on the basis of consistent succcess-though no one cartridge is so likely to dominate at distance (as the short range PPC champs)-there are too many substantial variables to balance (or juggle!).

Cost of course probably deters more experimentation in UK,but less so in US,where rewards are higher,costs lower.

 

I understand the appeal of 'the exception' especially if it's your own,but we really should all know that ultimately a one off,which remains a one off,rather does not disprove the general tule,but confirms it "one of them worked,but only one" isn't going to persuade many-probability is very low!!

 

"Many were cauld,but few were frozen" is as true of shooting as it is of temperatures in a Presbyterian Church (called/cauld/cold) or selection ( chosen/frozen)... and we all risk hearing damage...

 

g