Vertical dispersion at 600 yds to 1000 yds

Get or give advice on equipment, reloading and other technical issues.

Moderator: Mod

Message
Author
bsouthernau
Posts: 648
Joined: Sun Mar 11, 2012 4:31 pm

Re: Vertical dispersion at 600 yds to 1000 yds

#31 Postby bsouthernau » Fri Jun 10, 2016 9:12 am

johnk wrote:Belmont Small bore range has a cute issue some winter nights when you get a meniscus or the like between the cool night air & hot ground air that forms exactly on the line of the aiming marks, causing high & low eights was it washes like ocean waves.


I have never taken any temperature measurements on the smallbore range at Belmont BUT I have done a lot of radiosonde flights over the years. What happens is the air in contact with the ground actually COOLS first and this produces a very stable layer of air near the surface where temperature increases with height. I surmise that the phenomenon you refer to is fluctuations in the top of this inversion layer.

Barry

plumbs7
Posts: 1124
Joined: Wed Feb 12, 2014 7:32 am
Location: Dalby/ Tara Rifle Club

Re: Vertical dispersion at 600 yds to 1000 yds

#32 Postby plumbs7 » Fri Jun 10, 2016 9:32 am

jasmay wrote:So, the important question is how to manage it effectively?

Explaining the why and how is great, but what is of more use to shooters is how we manage it.


I know Dave will disagree with me on this Jason . And this is a lot to do with shooting at Dalby and Chinchilla rifle ranges and also others that have thick mirage ! I've personally found that running 60x in washing machine type mirage really throws the shot around like the group above ! Back off to about 20 x accuracy comes back a lot better ! That's anecdotal evidence , the scientific evidence from Dave's video experiments have proven otherwise ! :shock:

I guess the same that I've experienced with head and tail winds ! The theory and experiences are at odds with each other! I think my experience is more wind shier and aerodynamic jump ,
as the theory is correct!
Last edited by plumbs7 on Fri Jun 10, 2016 10:04 am, edited 1 time in total.

AlanF
Posts: 6952
Joined: Wed Jun 15, 2005 8:22 pm
Location: Maffra, Vic

Re: Vertical dispersion at 600 yds to 1000 yds

#33 Postby AlanF » Fri Jun 10, 2016 9:36 am

One way of looking at these sorts of conditions, is how to minimise your losses. If you can recognise early that vertical is primarily due to conditions, then you can have some confidence in "believing" shots and adjusting fully on them rather than writing them off as a mystery, and ignoring them at your peril. I'm usually very suspicious of vertical being attributed to conditions, but it does happen and the more we learn about it, particularly how to recognise quickly when it is actually happening, the better. In addition to recognising conditions, one of the key things that will help in this, is to be very confident about the accuracy of your equipment, and of your own techniques, then you'll have greater confidence to decide when a shot is significantly affected by conditions

plumbs7
Posts: 1124
Joined: Wed Feb 12, 2014 7:32 am
Location: Dalby/ Tara Rifle Club

Re: Vertical dispersion at 600 yds to 1000 yds

#34 Postby plumbs7 » Fri Jun 10, 2016 10:16 am

Ok last one ! I just want to say a disclaimer! With the up coming Nats which will be my first in open ! I realise that by putting up my testing and experiences has made me little bit of a target ( pardon the pun) truth is I'll be pooping myself on the 300 yd line in a couple of weeks ! So don't read much into my abilities as there are sooooooooo many world class shots ! I just need to take that pressure of myself or I'll know I'll crash and burn !

With that out the way ! This one is at Belmont again at 600 yds , 168 load which at 300 for 4 shots went through the same hole ! I blamed my rest and some is shooter error !
Image
What caused that ?? I won't keep u in suspense!
My rectile was out of focus! Redid it and it grouped again ! All be it with 180 load but yep was all over the shop!

The 168 Gr load in the above post with 3 shots side by side ( hardly a scientific sample but shows promise) is the same load !

look great threads that for me started at development squad and training sessions ! I think we have all benefited and had some real input from world class shots ! I will be reading over and over again a few time to get it to sink in! Kind regards Graham Sells Dalby/ Tara rc

ecomeat
Posts: 1121
Joined: Tue Jun 01, 2010 11:07 pm
Location: Pimpama QLD

Re: Vertical dispersion at 600 yds to 1000 yds DAVE's MIRAGE

#35 Postby ecomeat » Fri Jun 10, 2016 11:25 am

Hopefully this Photobucket link to Dave's time-lapse video that illustrates the image moving.
Click on the target image and the video should load up.
Image
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

ecomeat
Posts: 1121
Joined: Tue Jun 01, 2010 11:07 pm
Location: Pimpama QLD

Re: Vertical dispersion at 600 yds to 1000 yds

#36 Postby ecomeat » Fri Jun 10, 2016 11:45 am

plumbs7 wrote:Well that is the next thing is mirage !
Image
Another group pretty much the same load again but right on dusk with boiling mirage and slight left wind!

Graham,
Is this photo (a) one pretty ordinary 10 x shot group .....or (b) three x separate loads fired at the one aim point ?
I have seen it posted on a number of different Groups and threads, but still not sure what it is.
If it is in fact one x 10 shot group, what does it measure ?
Extreme accuracy and precision shooting at long range can be a very addictive pastime.

williada
Posts: 859
Joined: Wed Jul 22, 2009 12:37 am

Re: Vertical dispersion at 600 yds to 1000 yds

#37 Postby williada » Fri Jun 10, 2016 12:20 pm

Jason the coach’s job is so much easier if the gear is right. That is the message from Alan. But the coach’s need to lift their game too and be aware of the complexities that explain what is happening in a high performing team because the bar is being lifted all the time. That is the essence of these posts based on good science.

The coach’s personal attributes must include people management skills at the local level, but at a higher level, shooters should know what is expected of them. The coach must have keen observation skills and above all, mental arithmetic capability in light of the complexities of bullet flight these posts are trying to explain. There is no reference book that does it all. You guys are on the ground floor of what a few know and have kept to themselves.

I am reminded of what Al on Benchrest Central said about a plaque in his workshop. It goes something like this: “A person who learns to do a job well will always have work, but the person that learns why will always be their boss”.

Not everyone can do that unless their confidence and application is built with practice for reflexive decisions e.g. It is true Moe won the handicap pennant and the scratch pennant this year in a competition of 6 teams by a big margin as Alan and Michael know. It was not about the stars in the team but bringing the others up steadily from past performances and building on those levels. We have had a development program of sorts that helped individuals who wanted to be helped.

The conditions were such at 900 and 1000 yards, there were not many possibles, but there were on our team for good reason. The scores were poor at 1000 but streets ahead of the opposition and it was not because we stacked the handicapped team we won scratch too and both competitions for the year. We have also attracted and kept new members because we can develop them. It’s not like getting people on the bike and then getting them to press the pedals. It’s being patient and mentoring and explaining during a pennant shoot by the coach for some what they are doing as a coach, what they are looking at as they shoot and getting away from the trigger puller mentality, that’s a cop out, although there is an expectation being built in that all shots must be released at call within 8 seconds or less.

The coaches had a set of tables developed for mirage conditions and wind conditions which my wife and I have been trialing which also include spin drift effects. We are still trying to master them because of the interaction of mirage and wind and the interpretation of the mirage is in the eye of the beholder at times. Sometimes we just use the wind table then we drop that and use a mirage table if it appears and if its readable. This is, of course understanding your local terrain, as Norm talks about, influencing things. But Footsore can attest how well my wife shoots in TR on his visits from QLD and can keep up with FO shooters based on new skills.

The hard part on the pennant day was working out the mirage effect at distance because it occurs at the target. It is representative of apparent aiming mark shifts, but it also is representative of wind movements. We got the balance pretty right in this particular case. Yes the old 60/40 rule with flags which was broken down to 60:30:10. That meant the first third of the range was worth 60% of your wind allowance and the last two-thirds were worth 40% of your wind allowance. If we break the last 40% into further divisions, we were working on that last flag being worth 10% which became equal to the mirage wind correlation at long range because it is occurring at the target unless you focus up range and because over that distance different wind zones were operating on the day. That meant total mirage wind allowance could not be utilised for the whole range. So we used the flags and mirage combination for windage, but also applied a value for the apparent aiming mark shift which was doing people too and allowed for spin drift. It was just too quick at times and we got caught by elevation either low when it boiled or upper right when mirage density changed quickly when it backed off from a run or it flattened when mirage disappeared when wind was over 12 m.p.h. we went to the wind table. We had strategies in place which maximised our result even with less skilled shooters because the condition impact was greater than their holding ability. Yes it is complex but can be done.

All of the above is very hard to do when you are learning, but at least you should learn what has happened and why before you can accommodate it. We are not going to just hand this out unless you have been through a program of development and you understand the pieces that make up the puzzle. David.

DenisA
Posts: 1469
Joined: Wed Nov 09, 2011 7:00 pm
Location: Sunshine Coast, QLD

Re: Vertical dispersion at 600 yds to 1000 yds

#38 Postby DenisA » Fri Jun 10, 2016 12:47 pm

AlanF wrote: In addition to recognising conditions, one of the key things that will help in this, is to be very confident about the accuracy of your equipment, and of your own techniques, then you'll have greater confidence to decide when a shot is significantly affected by conditions


This is so important.

plumbs7 wrote:My rectile was out of focus! Redid it and it grouped again ! All be it with 180 load but yep was all over the shop!


I'm not picking on you here Graham and I know you know this already but I'd like to make a point since you've said the word.

It frustrates me when the term "setting focus" is used for rifle scopes, unless its setting the eyepiece for reticule focus which only needs to be done once. So many people, new and experienced that come and start shooting LR at North Arm don't realise or understand why it's more important to set the scope to "parallax free" rather than clearest "focus".
Of 4 scopes I have NF12-42 NXS, NF Comp, March 8-80x and a dodgy Nikko Stirling on my .22lr, none of them are often parallax free when set to their clearest point of focus. It's always just a touch off....... but still very clear.

IMO, the term adjusting focus should always be replaced with setting parallax.

As we all know, shooting at LR without being Parallax free, even slightly has the potential to open groups heavily. Especially in F-class where we're free-recoiling, floating our eye in front of the scope and not using firm cheek weld for repeatable eye position.

jasmay
Posts: 1068
Joined: Fri Sep 28, 2012 9:26 pm

Re: Vertical dispersion at 600 yds to 1000 yds

#39 Postby jasmay » Fri Jun 10, 2016 2:08 pm

williada wrote:Jason the coach’s job is so much easier if the gear is right. That is the message from Alan. But the coach’s need to lift their game too and be aware of the complexities that explain what is happening in a high performing team because the bar is being lifted all the time. That is the essence of these posts based on good science.

We are not going to just hand this out unless you have been through a program of development and you understand the pieces that make up the puzzle. David.


As I mentioned in another thread, the lack of a good development process is something Australian F'class shooting appears to suffer from heavily. I would love to see some form of development and coaching process implemented.

plumbs7
Posts: 1124
Joined: Wed Feb 12, 2014 7:32 am
Location: Dalby/ Tara Rifle Club

Re: Vertical dispersion at 600 yds to 1000 yds

#40 Postby plumbs7 » Fri Jun 10, 2016 5:48 pm

Hi Denis , no was rectile out of focus not parallax error.

The group is10 shots at about 500 m and is mirage effected. Like David said , it is a fish!
Sorry , it is measuring the effect of refraction aimed at the same little aiming mark!
When I drove to check the target I was like" what the ! " I've never seen anything like it before !
Of corse slightly wind effected from a left wind! Shot about 5:00 pm !

I just saying sighting and wind conditions can scew results ! All of the loads you have seen are all same . Except for the 168 Gr load !
Last edited by plumbs7 on Fri Jun 10, 2016 6:00 pm, edited 2 times in total.

DaveMc
Posts: 1437
Joined: Mon Aug 22, 2011 6:33 pm

Re: Vertical dispersion at 600 yds to 1000 yds

#41 Postby DaveMc » Fri Jun 10, 2016 5:50 pm

Sounds like "a rectile disfuncion" :lol: sorry couldn't help myself :twisted:

plumbs7
Posts: 1124
Joined: Wed Feb 12, 2014 7:32 am
Location: Dalby/ Tara Rifle Club

Re: Vertical dispersion at 600 yds to 1000 yds

#42 Postby plumbs7 » Fri Jun 10, 2016 5:56 pm

DaveMc wrote:Sounds like "a rectile disfuncion" :lol: sorry couldn't help myself :twisted:

Lol! Some how it was out , bumped cleaning ! Don't know but thing happen!

plumbs7
Posts: 1124
Joined: Wed Feb 12, 2014 7:32 am
Location: Dalby/ Tara Rifle Club

Re: Vertical dispersion at 600 yds to 1000 yds

#43 Postby plumbs7 » Fri Jun 10, 2016 6:04 pm

I think something that is important in nearly all of the groups there is a nice waterline ! If I had flags and spotting disks the groups would most likely have been better except the fish mirage one !

Anyway I think my neck is about to be strangled , so now maybe the time to bow out and wish everyone good luck in the upcoming Nats ! Regards Graham.

williada
Posts: 859
Joined: Wed Jul 22, 2009 12:37 am

Re: Vertical dispersion at 600 yds to 1000 yds

#44 Postby williada » Fri Jun 10, 2016 9:43 pm

I ask Tony to do me a favor again, at his earliest convenience, to post a copy of work I have done on a Nodal Pyramid with his results, as I can not upload to Photoshop due to my internet being shaped. The pictures tell the story. Time and time again I have seen this in formal testing. Tony's results are actual, on an electronic target doing a nodal ladder test without altering the sight. Just as I talked about the interaction of frequencies on group shape in another thread to determine group shape, the interaction is evident here as well as with aerodynamic forces. Mr Magnus and Mr Gyroscopic fight over Miss Yaw more than you think over a long distance. Those that believe in waterline groups are kidding themselves at long range. You have to manage the group and the examples demonstrate what you should be managing and why the wrong velocity node will make that so much harder. There is an address to lookup which also reviews various models. In that paper, Ross Mason says he feels something was missing from his model, I think I have touched on that. The author also mentions mirage. In light of what Dave and I have experienced, that perception is questionable too. Anyway, by putting things out there all our perceptions can be improved. We are only building on the work of others and are human too.

ecomeat
Posts: 1121
Joined: Tue Jun 01, 2010 11:07 pm
Location: Pimpama QLD

Re: Vertical dispersion at 600 yds to 1000 yds

#45 Postby ecomeat » Sat Jun 11, 2016 10:27 am

Williada's Nodal Pyramid as requested. Davids internet has some issues and wont be fixed for a few more days, so hence the request for me to post it. Sorry for the delay.....not long out of bed after shift work :oops:
I think I might have put my original Hex target up on here last year when I used the ETs at Belmont to do a Ladder Test at 800 yards.
The following was the Williada assessment of what could be gleaned from the exercise.
Its a good example of what David refers to as the harmonics in the barrel resulting in a change in the axis of the elipse, when a useful number of shots are sampled like this.

Image
Extreme accuracy and precision shooting at long range can be a very addictive pastime.


Return to “Equipment & Technical”

Who is online

Users browsing this forum: No registered users and 20 guests