Acceptable ES at 1000 YDS

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BRETT B
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Acceptable ES at 1000 YDS

#1 Postby BRETT B » Wed Dec 21, 2016 10:06 am

I'm looking for information on what ES I should expect at 1000 YDS at the Target Face relative to the ES at the muzzle !!

With the SMT system it shows you velocity through the Target . I then realised there were many factors that will effect velocity and ES at the Target .
If we use a Berger 180 Hybrid as an example , what would be the average % of BC difference of each bullet in 1 box??

Slight differences in OAL and Base to ogive length will have small effects on BC but large effects on velocity at long range so I am trying to figure out a base line to work off.
Just say as an example you have a good load with 10 FPS ES at the muzzle what would you expect at long range?? 20 FPS, 30, 40 ??

IN the small testing I have done with a Magnetospeed on the barrel then compare through the target I am seeing an average of 3x the ES at the Target face.
Any info I can get to form a baseline would be great as I think this could be a very useful tool when tuning at long range..
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

AlanF
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Re: Acceptable ES at 1000 YDS

#2 Postby AlanF » Wed Dec 21, 2016 11:03 am

Brett,

I seem to remember a discussion about the precision of the SMT velocity measurement, and it wasn't claimed by the manufacturer to be up to chrono standard, so at least some of your higher ES at 1000 would be due to that. A recent experience of mine didn't show too much deterioration at 1000. I calculated that a SD of 7 fps would probably hold the 6 ring vertically at 1000. I developed a load that gave 7.25 fps SD with a Magnetospeed, and then shot at 1000 and it held the 6 ring (with a 60 8) ). Not sure how repeatable that would be (10 shots is a small sample size).

Alan

BRETT B
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Re: Acceptable ES at 1000 YDS

#3 Postby BRETT B » Thu Dec 22, 2016 9:04 am

Alan ,

So far I have found the Chrono on the SMT to be more accurate than I had expected . I just don't know what you would expect at long range through the target as I have never seen any data like that before.

I have used my own rifle and many others now and to my surprise I am seeing a trend for ES at the Target Face relative to muzzle ES.

1 example was on my 7mm at 800m I had 11 FPS ES over 10 shots with Magnetospeed and the Target showed 29 FPS ES . That was with untouched bullets straight out the box . From memory the bullets were doing an average of 1910 fps through the target face and 2955 at the muzzle. I know there must be a rate of decay for ES/SD as distance increases but not sure how much yet.

Brett..
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

williada
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Re: Acceptable ES at 1000 YDS

#4 Postby williada » Thu Dec 22, 2016 10:08 am

Brett, you are on the right track but I cannot give you actual figures for 1000 yards for the Berger 180’s which I have on order still, to use with a reamer to test a couple of new barrels.

May I say what you have found does happen at 1000 yards, as I experienced similar things machine rest testing at that distance (many years ago) which led me to consider a nodal pyramid test and perhaps why the relationship between the Magnus Force and gyroscopic twist led to elliptical patterns IMO. Then I noticed this was more pronounced when wind oscillated in a zone just above and below 10 mph. A few tests would not have picked this up in isolation. It is significant and there are lots of variables to discount when trying to determine the causes of the real group size.

I don’t want to get too heavy with technical discussion but the drag forces do alter the anticipated BC as the projectile changes orientation and so keeping velocity up is one way of countering the problem. Sorting bullets and batching is a good idea to give more meaningful results as would be pointing bullets or selecting VLD’s in the appropriate environmental condition. This needs to be verified in the modern context and the electronic targets would be a good source of information for a general appraisal. As JohnK suggests, you can take measurements and use a ballistics program. Do this if you are not game enough to place a chronograph in front of the target face at 1000 yards after sighting in on a benign day as well as placing one in front of the muzzle.

With any approach, you have to be aware that your barrel lift may have a different result compared to other barrels due to its compensation profile which will affect what you think is an acceptable ES when you are starting to measure these very small differences. By all means use a MS on your barrel for testing to see the relative differences in BC. However, you cannot use it in a match and this may change your compensation profile with it off as would a muzzle weight or tuner.

For all practical purposes which take into account very minor variables whether it be BC, ignition or compensation profile it is easier to broaden the tune. I use seating depth to achieve that having run through charge testing, then if I want to go further I add a tuner or muzzle weight.

For those who want to know what I do with seating depth, I will post a graphic on Adam’s thread relating to load tune or barrel tune.

In closing, the effects or light and mirage really move your groups around at 1000 yards. Light tends to draw your aiming to the sun angle. Light up and down due to cloud cover also alters your aim point. Mirage if it boils tends to shove shots low, not high in Australian conditions if the light is constant. It’s a difficult mix at times, you really need a machine rest to discount these effects which can become academic.

Norm
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Re: Acceptable ES at 1000 YDS

#5 Postby Norm » Thu Dec 22, 2016 10:18 am

Brett I would not worry too much about the velocity that the SMT gives at the target unless you are shooting in good conditions.
We have had a close look at the results we are getting and the data seems to be effected a bit by the conditions.
In good conditions the results look quite good and match up with what you are finding, but the same loads shot at a different distance under very strong wind conditions where the target was moving about a bit did show a much greater shot to shot velocity variation.

The velocity data is quite handy but be aware of the systems limitations when conditions are rough.

Now the next generation, 10 sensor SMT system should provide some very useful information. :wink:

AlanF
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Re: Acceptable ES at 1000 YDS

#6 Postby AlanF » Thu Dec 22, 2016 1:27 pm

Brett,

Did you notice much correlation between POI and velocity at the target? Did the bullets disperse vertically as much as the 1000yd velocity suggested they should? I know that this could be affected by some compensation, but at 1000yd very unlikely to be enough to hide the velocity induced trajectories.

Alan

ShaneG
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Re: Acceptable ES at 1000 YDS

#7 Postby ShaneG » Fri Dec 23, 2016 8:24 am

Hi Alan
We had a team practice after the NQRA Queens on manual targets at 900M.
One could predict the elevation of the shot from the Lab Radar velocity reading prior to the target reappearing from the pits.

Low V = low 6 or maybe even a 5?
Same with higher V.
The LabRadar is the most accurate chrono Peter S or Dave Mac have encountered.
We tested 2 side by side here last month indoors and their SD was 1.
Peter believes them accurate enough to test primers.

I would seriously question the accuracy of the SMT at the target?

Merry Xmas

williada
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Re: Acceptable ES at 1000 YDS

#8 Postby williada » Fri Dec 23, 2016 9:43 am

Using something more accurate than an SMT at the target at 1000 yards would be great to explore. It just might confirm Brett's general observation as to whether the BC has changed significantly at this distance. That is an issue which still exists where there is room for further improvement and for managing elliptical groups and IMO is separate to component selection in terms of primers and powder for internal ballistics which impact on the flight path.

The trade off maybe in rifles being required to perform at higher velocities at 1000 yards which is past their sweetest spot. The Lab Radar will will greatly improve component selection to keep SD's down when operating outside the rifle's sweetest spot. Not all nodes are equal and from my experiments there is generally only one good one when we are starting to examine very small differences.

We could refine the trend analysis with large samples as I have done in the past using two chronographs, one at the muzzle and one at the target. Norm has noticed the SMT systems on windy days create target wobbble which may interfere with the sensor system. The group pattern is what interests me because it is alternative way of reviewing the data.

Alan's statistical analysis of Queens events was revealing scores blew out past 700 yards. When we look through the records of top shots on electronic targets now, we now see on the Hexta system at 1000 yards, we see the groups are not small. The Lab Radar will certainly enable people to reduce the margins through better load development and determine sound tunes and you guys are to be commended for adding to the pool of proof.

It would be great if every shooter could get hold of a Lab Radar, but I believe they are restricted. However, the traditional methods for finding nodes or using mild compensation will still work well and you can still batch primers and components as people do. That part has not changed. Shooters should be re-assured, they will still remain in the hunt. The data from modern equipment will be compelling for the doubting Thomas's. That is great work.

BRETT B
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Re: Acceptable ES at 1000 YDS

#9 Postby BRETT B » Fri Dec 23, 2016 11:00 am

Thanks for thr replies . I will be mindfull when tuning barrels of the limitations the SMT may give in terms of velocity .

Alan i will be doing some testing over the xmas break so i will send you some screen shots for your curiosity..
BRETT BUNYAN F CLASS OPEN SHOOTER W.A.

johnk
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Re: Acceptable ES at 1000 YDS

#10 Postby johnk » Fri Dec 23, 2016 11:13 am

williada wrote:Alan's statistical analysis of Queens events was revealing scores blew out past 700 yards. When we look through the records of top shots on electronic targets now, we now see on the Hexta system at 1000 yards, we see the groups are not small. The Lab Radar will certainly enable people to reduce the margins through better load development and determine sound tunes and you guys are to be commended for adding to the pool of proof.

If that analysis were at Belmont, then you have the additional issues of the high mounds at 8, 9 & 1000 & the potential for "ski jump" shot position changes with variable quartering winds coupled with the who knows effect of that noise mitigating berm behind 1000 & to the West down to 900.

I think that the 2016 QRA Queens was indicative of the issues caused exemplified by the extraordinary number of shooters who clipped an adjacent target with their sighter(s) at 1000 yards & the consequential moans of the owner sindicates.

williada
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Re: Acceptable ES at 1000 YDS

#11 Postby williada » Fri Dec 23, 2016 3:50 pm

John, your observation has a great deal of merit, but I think Alan was looking at a bigger picture when seeking answers to his observation. The big picture at the longs if I may indulge, is made of lots of compartments to distill e.g. components in load development, compensation profile, projectile stability, spin drift, Magnus and gyroscopic forces, BC decay, light and mirage as well as zones of terrain which affect wind flow and pressure and transonic zones if the projectile happens to fall below the speed of sound. Now throw in poor armouring, ignition timing, barrel harmonic length, stock imbalance and lack of wind reading experience at the longs, and the picture becomes cloudy.

Through different people sharing experiences and ideas and having them tested on the range we can work out in percentage terms what elements of tune are significant for improvement next time. People’s processes maybe different at times, but we are all seeking improvement which is good to pass on. It’s not a contest, but a path of enlightenment for new shooters based on the experiences of us older farts to marry with their own ideas. I am impressed with the education level of younger inquiring minds who will build on what we know. The wheat soon gets sorted from the chaff if we can shortcut some of this stuff to begin their journey.

This enables shooters to develop a strategy for the venue or conditions to best cope with them because we can.

The Belmont Range is a case in point. I remember a couple of years ago the same issue arose at the longs. A few eyebrows were raised when suggestions were made that an accurate low node chosen by some did not have enough legs to push through conditions and perhaps a different choice of projectile may have been better suited to those conditions such as a tangent or hybrid projectile rather than the twitchy VLD.

It becomes a skill in managing a larger group with higher velocity and low SD’s unless the higher velocity compensates a wee bit at 1000 yards, like Cam did at the ton, in similar conditions a couple of Queens back, at Belmont

Specific testing was done at Belmont to revisit this stuff, and kind of added to the evidence with the nodal pyramid test we published. Top results at the longs this year in the Queens again confirmed that experience, not that anyone cannot get caught in conditions. Its amazing how a better tune for conditions finds more relief whichever way you do it. In nil wind conditions, sometimes the projectile can lack lift if you tuned it in rougher conditions and as a consequence groups suffer and at 1000 yards and beyond, groups may turn elliptical in certain circumstances. There are a few tangents.

Of course varying the muzzle weight and bloop tube length can move nodes to better suit higher velocities which are better at the longs, in those conditions you mention. It’s all a trade-off.


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