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Thoughts on 1000yd bench rest


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You don’t need a gun that can shoot .1″ groups at 100 yards to be competitive at 1000 yards. Long VLD bullets often do not shine until 300yds since they may not fully stabilize inside 100 yards. The 300 yard-line is where you can assess whether a gun has what it takes to do well at 1000. If you can group at or under 1″ at 300 yards, you’ll be in the running at 1000 yards.

 

 

I have quoted this directly from an article featured in http://www.accurateshooter.com/competition/1000-yard-benchrest-guide/

 

I wondered what the thoughts of the more experienced 1000yd shooters were, in particular the point about the bullets not stabilising properly at 100yds.

 

I have shot quite a few 140gr Bergers Hybrid groups into the .1s at 100yds, surely they are stable at that point?

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Personally, I think that theory is inaccurate! I cannot prove it, but I do not believe that VLD bullets 'go to sleep' / stabilise at say 200/300 yards from the muzzle but not accurate at 100 yards. I do most of my testing initially at 100 yards and if it doesn't group at that distance I will try a different load, cartridge base to ogive measurement.

 

I have used VLDs in various calibres before (6.5/7mm) and found them to be pretty accurate at 100 yards during initial testing.

But I now only use Berger Hybrids in 6mm and 7mm which are excellent from 100 yards and out and are supposed to be more tolerant on bullet jump than 'finicky' VLDs.

 

Maybe another couple of benchrest shooters of long standing - Vince Bottomley a.k.a The Gun Pimp or perhaps Laurie Holland could chip in with their thoughts.

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Okay , someone please enlighten me , if a bullet is unstable within a certain distance how does it get back on track and find its way at a further distance , I understand it may be more stable at slower speeds ( so further away ) but by then the unstable bullet would be heading towards an unpredictable point surely ?

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I've never seen a competitive 1000 yd gun than wouldn't shoot tiny groups at 100 yds.

 

So, I don't agree with the theory that bullets don't stabilise at 100yds - and yes, I've heard it said before - but never by a 1000yd BR shooter.

 

But I do agree totally with the bit about "under an inch at 300 yds, you'll be in the running at 1000 yds." This is exactly what I look for when developing a 1000yd load/gun.

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I should add however - I've been caught out by using a 'stunning' 100 yd load at 1000 yds.

 

You can shoot one-hole groups at 100 yds that don't work at 1000 yds - if velocity spreads are too great, it may well group nicely at 100 yds but it will show up spectacularly at 1000 yds!

 

That's why 300 yds is a good test distance.

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Have to agree with Vince here if i have a load that doesn't shoot at 100 i have found it doesn't get any better further out. After extensive load dev for my dasher i have dound that a decent 100 yard groups will be eratic at 200 but decent at 300 again this i can not expalin. When i say a decnt 100 yard group I mean less that .3 moa for a five shot group.

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I should add however - I've been caught out by using a 'stunning' 100 yd load at 1000 yds.

 

You can shoot one-hole groups at 100 yds that don't work at 1000 yds - if velocity spreads are too great, it may well group nicely at 100 yds but it will show up spectacularly at 1000 yds!

 

That's why 300 yds is a good test distance.

 

 

Does Diggle offer the option of 300yd testing off the bench Vince?

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How often is the 300yard range open Vince? I would like to do some longer range load development.

Laurie mentioned a while ago you guys meet up on Thursdays, are you mainly shooting over 100 or 300?
ps I tried to send this to you via PM but it says you can't receive any more message, maybe your inbox is full?
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I have quoted this directly from an article featured in http://www.accurateshooter.com/competition/1000-yard-Benidorm TG chrest-guide/

 

I wondered what the thoughts of the more experienced 1000yd shooters were, in particular the point about the bullets not stabilising properly at 100yds.

 

I have shot quite a few 140gr Bergers Hybrid groups into the .1s at 100yds, surely they are stable at that point?

 

Alan, This article from Accurate Shooter hasmany sesible comments on 1000y shooting,butneeds to be seen in context-it's a little dated...eg though 6mm,6.5mm still figure,30 cal less so,as in the article, it's the better 7mms that are setting the pace now.It woulsld have benefitted too,from some ediing in places-Precision and Accuracy (Litz) are not consistently identified.

 

OK,but your central point comes from the quoted comment "You don't need a gun that can shoot .1 groups at 100y..." This is indeed true (not many rifles do this consisrtently-but he is saying it for 'effect' -and it does not say a .15 rifle won't do.....this is VERY clear in part 11 (same reference) where he obligingly and much less controversially says "But even the best wind wizard won't prevail without an exceptionally accurate gun-one able to put 5 shots into .25 or less at 100y"

 

Now that is much closer to the experiences that Vince comments on-and others- that is,an inch at 300y is a very good criterion for a very good 1000y rifle.

He confounds his misleading ".1" by restricting to VLD bullets-all the rage at the time of writing,but have now given way to the hybrids,for example. It is often recerded that the VLD design is/was rather sensitive (to seating depth,maybe other design issues)-BUT attributing that to "VLD bullets often do not shine til 300y since they do not fully stabilise at 100y" seems to consdierably overstate the meagre data on this-very meagre.Les puts his findings very clearly,and are in line with most. Fiddly VLDs,maybe,but not better at 300 than 100. There have been a few speculations about short flight (sub 300y?) aerodynamics-including a spiraling nose due to overly fast rifling ('nutation' or even torque free/induced precession....don't ask!!),but not empirically established for bullets,which overwhelmingly just shoot larger groups with distance.

There is any amount of data that (almost?) all bullets are fine-and groups get bigger with distance (though not strictly linearly-as other factors come in-one reason MV SD isn't a big issue for 100 BR,but very definitely is for 1000y. (300y for score is big in USA,and 300m CISM likewise in Europe-though not with VLDs. I haven't seen any smaller 300y groups from my 'score 30BR' or 308CISM than they do at 100y,though I have not shot hundreds of such groups in balanced conditions,and none with VLDs.

(Mark-were yours with VLDs reliably better enough at 300y,,under near identical conditions?)

 

OK,seen thus, the article,is much less contentious,and has lots and lots of information about1000y shooting,even allowing for the earlier date.

 

Some of the 'mental game' points likewise are not consistent-he is not usually talking about the inner "zen" game (as in tennis or golf-but he doesn't use the term either-it's just 'mental'- but not distinguishing eg 'confidence' from the cognitive firing solutions mentally calculated by the shooter/ballistic engine to allow for the shooters'judgement of wind. That latter is one aspect of 'Accuracy'-how the shooter hits the target,centrally.

 

Basic point,he is really saying you need a rig with sub 1 inch precision at 300y,and Shooter Accuracy skills to bring the shots onto target.Amen to that-though depending on the target size,and distance,reducing the rig's (sub moa ) grouping may have variable returns.....a hit on the edge of a gong is a hit nonetheless-if shooting for group size,smaller is advantageous,as it is for scores.

 

600y (competitive) shooting is available,and pro rata should serve rather well,as in the Diggle winter series.

 

 

As Vince says,300y isn't too popular here. I'd think .25 at 100 (with a 1000y ballistically capable load,of course-the 30BR or 6PPC can't hack 1000y) woud be encouraging,and (sub) 2" at 600y even more so...see the Diggle results...many shoot 1000y BR in the wintr series

 

Enough,it's a rugby day.... :-)

 

g oval bal

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How often is the 300yard range open Vince? I would like to do some longer range load development.

Laurie mentioned a while ago you guys meet up on Thursdays, are you mainly shooting over 100 or 300?
ps I tried to send this to you via PM but it says you can't receive any more message, maybe your inbox is full?

 

Al - pm me on vinceb@targetshooteronline.com

 

A few of us meet on a Thursday but we usually shoot 100 yds - however, if you want to come down, I can always make an excuse to shoot 300 yds!

 

At the moment, the weather is iffy - the GB F Class League boys have had a rough time today - I say 'boys' because the girls have done rather well!

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  • 3 weeks later...

Okay , someone please enlighten me , if a bullet is unstable within a certain distance how does it get back on track and find its way at a further distance , I understand it may be more stable at slower speeds ( so further away ) but by then the unstable bullet would be heading towards an unpredictable point surely ?

As far as I understand it the theory is based on the fact that bullets are travelling fastest when the leave the muzzle and are subjected to higher levels of aerodynamic torque at these higher velocities. At this point if the bullet is not adequately stabilised it can harm accuracy and BC. The velocity begins to reduce along with the bullet RPM. The velocity reduces at a higher rate than the bullet RPM . With the reduced velocities comes reduced aerodynamic torque. This means that the stability factor improves; this is what people refer to the 'bullet going to sleep'.

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Hmmmm....it's speculative (the spin overstabilisation). Even the complex analyses don't deal with it directly,if at all-though of course overspinning has disintegrated bullets downrange for many decades(less as bullet jackets got better)...more a nightmare than a comfy doze off,though!

I does raise some issues that bear on ballistic predictors too-in a nutshell,they are somewhat compromised and tend to be 3 dof based .Bullets can move in 6 ways-linearly up/down,side/side and forward (but not back!);and can rotate about these thre axes (yaw,spin ,etc). So a bullet in flight can be desribed by just these 6 'dof' ( roughly,6 ways it is 'free' to vary).

^dof models are very good-spin drift,yaw,epicyclic swerve are accounted for-but it's very complex-there are aerodynamic coefficients that make BC seem simple,and these complex coefficuents are not easily measured,and can be non-linear just to complicate more.There were-until recently-few bullets so desribed (all military-so they can have 6dof for artillery).

Tough on us targeteers and sportshooters?....well, there are two saving cconsiderations.

It turns out we can do quite well without the rotational effects (3 of the 6 dof) and maybe better yet,recently Lapua has released a 6DOF program that uses far more data (either calculated or Doppler observed)-for a selection of their own bullets.

But remember the better 3 DOF methods do pretty well for rifles-like the Point Mass ones.

The fly in the ointment is drag-which is all we need for Point Mass,but though drag varies rather smoothly both above and below the speed of sound,around Mach 1 it does not (though bullets differ in detail),in general near Mach1 the drag coefficient increases very rapidly,peaks then decreases much more gradually....(loosely refered to as 'transonic-but it's a catastrophic change just at Mach 1,before it tails off much more slowly..

This means there is no simple easily solved equation(s) to model the bullet's drag curve....so plan B was used...cheat (ie simplify,and accept a small error-put very basically,solvers sample the bullet in flight every .001sec,eg or every metre of it's flight (smaller bites are better,but more calculation...

With fast hand sized computors,the sampling could become increasingly sophisticated (shorter time and distance slices)-but all done very very fast and fairly easily programmed (for the ballistic engine designer).

The Point Mass system users won't all agree exactly (different time/distance slices etc) but they will be close,and 'good enough' .

Near enough, the underlying maths of the Point Mass solvers is using Drag Coefficient (Cd) or at least the 'standard drag coefficients' (like G7) which are very specific to 'standard' projectiles and will do until "we" get Cd V Mach numbers for your actual bullet-which is what Lapua are beginning to provide...as above...with Hornady maybe (at least theyhave a Doppler?)

Meanwhile we have pretty good predictions, using bullet/scaled BC G7 fits.... (as Litz).

As is becoming clear on forum,when firing data don't fit predictions from the solver ,it's not the ballistic solver-it's the input...GIGO ( garbage in ,garbage out remains true,but it doesn't need garbage-if several inputs are just a tad off,BC 4%,MV 2% ,scope clicks .5% ,range 1%,scope height 3%,etc error is cumulative and will give a long range error.

So 'true it up'? ie just tweak a few variables til it fits your (100 or 200y ) data......hmmm....you will run a real risk of worse error at other increasing ranges,and if you 'tweak' more than one input,you will lose touch with the actual physical reality of your measures,and just get in a ...mess.Better by far to actually measure more acurately to begin with.

 

(so no 3 shot groups of several inches at 300y-where will the fourth,fifth go?-better shoot them and see...and have a way more accurate drop input.

 

Did you go to sleep.....well,it's pretty complex....but the take away is :sensibly loaded bullets don't,it's not a worry;but get your basic ballistic input data really accurate.

 

Decent measurements get the job done.Don't skimp on the most important data you will collect,and use .

(you wouldn't check a coin's lack of bias with just three tosses ...if your annual ammo costs were about to be bet on....would you? :-)

 

gbal

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I wish I could find the video of bullet flight characteristics that John C of ex HPS fame told me about and provided the link to. This was at least 5 years ago but John and this model explained bullet stability like this:

 

When the bullet leaves the muzzle it is influenced by the barrel harmonics which makes the bullet fly in a snaking motion, both up and down and sideways at the same time. The model showed this as a 3D clover leaf movement that diminished over distance, getting smaller and smaller until the bullet path was completely stable. This distance, on the model, was 183 yards and it held true for most bullets. The distance of absolute stability varied depending on initial MV but it was always at about the 183 yard mark. If you look at night shots of tracer bullets you'll see this effect somewhat exaggerated.

 

The experimental method to establish this was understandably complex and involved careful; alignment of targets at precise intervals and measuring the deviation of impact points.

 

If you research the flight of arrows when leaving a bow it gives some idea of this snaking motion. I know the cause is not the same (archery was my sport for years) but it demonstrates the motion quite well.

 

Of course, the argument will always be that regardless of stability, even an unstable bullet that hits the same point every time is precise and accurate and will be at 100, 300 and xy yards distance.

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Meanwhile, BR for score (rather than group on a largish sheet of target).

 

US 3oo y Bench Rest for score is quite popular,but not in UK .THis just has the familiar rings scoring outwards.It gets pretty tight,of course....so much so that the dominant 1/200 group cartridge -6PPC- isn't the cartridge of choice,and the BR is-but not the relatively familiar 6BR (good for real accuracy to 1000y in benign conditions)-nope,its eclipsed by the 30BR....very nearly as accurate at 300y,but that bigger hole (.30 rather than .264) just clips an inner ring often enough more to make a competitive differnce.

Hit/group/score are of course simply alternate 'measures' of precision-(actually and/or accuracy,which is precision as extracted by the shooters skills). The measures can be combined-though it's pretty arbitrary what weighting should be given to either...

If the 'target' is very small indeed(relative to range,of course) precision grouping (ie minimal dispersion of shots) will come in much more critically ( a good 100y BR group would have hit the fly every shot,and a fly is smaller than a 'figX'-but hitting either are just different skills -emphasising different criteria for precision (engineering/ammo) and accuracy (shooter decisions/skill).

 

Mutual understanding and appreciation helps-just as the differences in disciplines all contribute to enhanced performance for shooters generally.

 

gbal

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I have quoted this directly from an article featured in http://www.accurateshooter.com/competition/1000-yard-benchrest-guide/

 

I wondered what the thoughts of the more experienced 1000yd shooters were, in particular the point about the bullets not stabilising properly at 100yds.

 

I have shot quite a few 140gr Bergers Hybrid groups into the .1s at 100yds, surely they are stable at that point?

i prefer mine to group at a 100 and see what happens at a1000 personally if i have a barrell that i cant get shoot at 100 ill change it and when i say cant get i mean sub 1/3 moa agg for 5 shots

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mmm....the John C/HPS/snaling model is interesting...presub=mably the testing involved thin paper sheets the bullets passed through at increasing distances,and dispersions were then measured.(?). Such data would indeed be worthy ofsome study.

 

The whole idea of bullet dispersion being less at some greater distance seems counter to the casuaal-and more careful -experience of most shooters-bullets impact targets with more dispersion as distance increases. But "flat earth "held sway for a long time.

Where might we look for data....bullets in large samples being fired at near identical velocities by similar launch rifles and skilled shooters,and impacting on various distance targets,which are then measured for dispersion very accurately....?

 

Well,first thought is to consider Bench Rest shooting competitions.Lets take the common distances,100y and 200y (183 would be nice,but this is a field observation-you take what is there...and it's 100/200y ). But there is a vast amount of shots so fired-25 shots to measure at each of 100y and 200y for maybe 100 shooters at just one big comp in USA....with both Light and Heavy Gun categories,and there are dozens like that every year....for over 30 years....what a sample! You could be selective indeed wrt atmospherics etc and still have big samples.

 

OK we also have a good control-each shooter fires at both 100 and 200y,25 shots to be measured at each-of course they are not identical,but that hardly matters (and they are quite similar-or at least the topx will be (.2 won't separate the top bunch of shooters)

So,with very closely controlled rifle-often the same one for both distances,and even betwen light and heavy class-again it matters not-as the crucial control for each comparison-group dispersal at 100y and at 200y is very good-same shooter,ammo rifle,etc often on same day-or similar etc etc....any small variations-the same guy doesn't always win eg- are controlled/balanced out over the huge samples....so what would we expect.....

Do the groups at 100y come in larger than the groups at 200y......(averaged out of course,but also compared any way you wish (how many are smaller at 200 than at 100 etc)....??)

well.......errr .... no.

 

Would the 183y groups have been smaller.....we surely can't have any confidence in that...but if the bullets were truely stabilised(as per model) at 183y ,they would not have dispersed at all in the next 17 yards....but they did...unless some other rather substantial new factor comes in (which is why my earlier head spinner post on the extra (missing) 3 dof for rotational dynamics might come in,but it's not obvious how.....have the state of the science ^DOF models missed this 'going to sleep' ....NO, dispersion still seems fairly angular (plus other increasingly influential factors,like coreolis etc etc....but it's well beyond 200yards before they really make much difference.

 

Angular dispersion (moa type-starting at the muzzle -but picking up more smaller dispersants as distance increases...) seems a fairly robust approximation...at least for the ballistics typical of 100/200 Bench Rest shooting,based on this vast data base.

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One of the guys shooting 1000 yds on Sunday also shot the same rifle in the 100 yd comp the day before. He shot a best 5-shot group of 0.251in at 100 yds and 6.9in. at 1000 yds.

 

I've never had a good 1000 yd gun that won't do it at 100 yds. If it took 180 yds for bullets to 'go to sleep', 100 yd benchrest would be a farce.

 

Most of us started shooting 100 yd benchrest with whatever we had and you'll see plenty of evidence on Diggle's Wall of Fame of sub quarter MOA from many cartridges - including 308 - at 100yds

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