ES & SD NUMBERS WITH ACCURATE LOADS

hi
do low numbers on extreme spread & standard deviation always corallate to the smallest group?
or do on target results vary?
thx for any help

 

Many will say no, and the only thing that matters is what the target prints. I think they are a good indication that your reloading process is going the right direction, and if your numbers really suck its a good indication that you need to look for problems. Some powders and load combinations make better numbers than others with all other things being the same. So my final answer is that i believe its an indicator only.

 

Absolutely not.

 

Simiply . . . NO.

It can vary depending on how a particular load works with the harmonics of your gun/barrel.

I look to my ES's and SD's to tell me how consistent I'm loading my ammo, not so much as to results on the target. I've had single digit SD's and ES's that didn't give me the small groups I was looking for and larger SD's and ES's that produced bug holes. However. . . if one has large ES's (usually large SD's are in conjunction), one is not going to see small groups. So, there's a certain point (depending on the cartridge and gun) where a meaningful relationship diverges. As long and I'm loading to get small ES's and SD's, I can focus on and refine other elements involved to get me to those elusive bug holes.

 

As said above. Low numbers correlate to good brass prep and loading. If your seating depth is off, the target could look terrible. Low numbers is just the start. Seating depth test would be needed next.

 

If I were shooting one rifle and one load at a known distance, I would not even use a chronograph. Say I had a "dedicated" 1000 rifle for competition, to be used only at 1000. What prints on paper is the final arbiter of what load I would use. However, if your intent is to use that rifle at various distances and need one load to shoot those various distances, low e.s.s and low s.d.s become mandatory. I shoot 3 rifles at 500, 600 and 1000 yards. None are "dedicated" to any one distance. I must keep e.s.s to a minimum..

 

In addition to what others have mentioned, it's also worth reiterating that ES/SD values must be considered with sample size in mind. You could measure velocity for 10 x 5-shot groups in a row with the exact same load, and I'd be willing to bet that some of the ES/SDs for the individual 5-shot groups would be good, some "ok", and some poor even though they were all the exact same load. In other words, the ES/SD values for an individual 5-shot group could differ markedly from the overall ES/SD for all 50 shots.

Shooters often aren't shooting groups of sufficient sample size (n) to obtain solid ES/SD values (i.e. 5-shot groups or less). We do this for good reason; largely to preserve barrel life and not spend a fortune on reloading components. Nonetheless, sample size has to be considered when evaluating velocity data.

 

My 6BRX......All three matches shot in about 3 hrs. Cool morning and warm afternoon. Same gun and loads. Conditions a little switchy and right to left. Velocity and SD went up on each match. Group expanded as SD and Velocity grew. Not much butt.......

 

What did labradar or on the firing line chrony say? My labradar and target data don’t say same as far as ES/SD. Seen it numerous times. Over several different shooters data and experience

 

Why ever would you expect them to?

 

If they ever do, buy all of that Lot of bullets you can.... lol
Unless your in a tunnel with a controlled environment, highly doubt you will ever see it happen.

 

I think it would be great to have Adam chime in on the absolute accuracy of that on target velocity.... on target you are measuring velocity between the two sensors on each corner.
Let's call that 6" so the math is easy.

You data is 2180fps over a 6" window.... SO ...

.5 feet / 2180 feet/s is .000229s just shy of a 1/4 milli second.

Lets say that the ShotMarker is accurate to +- 10fs.. (.5 / 2170) - (.5 / 2190) … that would require that unit to be able to accurate detect 2.1 MICRO-seconds different in two shots.

Hmm... that seems very fast to me.

I encourage you to graph Shotmarker velocity vs LabRadar Velocity. Here is one of mine.. different dot colors are different charge weights.



I trust my LabRadar much more than the ShotMarker….

and just for fun.... I also graphed ShotMarker "Y" value vs LabRadar vs Charge Weight.




Here you can see the rifle nodes at 2790 and 2825 according to this chart..... and this is exactly what I see "on paper" 50.86 is tight with flyers.

Just the geek in me coming out.

 

Because BRXbrad said it appeared the groups were better and could see group expand and grow as SD and velocity grew. That’s why I was stating that. Can’t really use target data on those units as the other members seem to agree on in the above posts

 

SD should be binned and never thought of again. ES is the game player and should be in single digits. I look for a graph like the one above (2818 to 2835 ) across a least three loads that increase by .2gns at a time. Projectile just off the lands. The barrel has just showed you where it is happy at pressure wise. The wider the node the less the daily atmosphere pressure will affect your barrel. when loaded in the middle of the plateau. Now starting with your tuner flush with the muzzle shoot at 100 turning out one eighth of a turn until you have perfect vertical line then keep going out until you have a perfect horizontal line. The setting halfway between the vertical and Horizontal is where you need to be. When you have done this as many times as I have you will recognize where the halfway point is on the way out 2 or more stacked. Centre zero scope at this setting go to 600 and check group it will need adjusting because of further distance maybe an eighth turn either way. I like a slight egg shape group up this shows a more true wind shot. Do this again at 1,000 note the settings. Hint if your rifle starts banging , kicking hard or torqueing
move the rifle forward in your rest or the bi pod back before you adjust the tuner. Weight forward of rest or pod don't weight the stock.

 

Now that others have had a chance to respond, I'll finish the "butt..." The data that was shown was all the data given during the match on my target. We were not shooting in a sterile environment, the was no Lab-radar on the line, etc. It wasn't a science experiment. We were competing at Borden, Ind. so that tells me that other factors influenced the outcome of each match and totals for each competitor. Below are those results. Now that I made more data is available, it doesn't appear that ES/SD are the deciding factors or are they? I don't know what the other competitors numbers were. I only know that I had a good day. In my mind SD equates into vertical spread at long distances. I use ES/SD to judge the consistency of my loads. I use those numbers during load development to find the most consistent powder charge. After that it's seating depth, tuner adjustment, and time at distance to prove loads. My load testing is done when conditions are as sterile as possible usually very early in the A.M. or late in the afternoon. I have done this long enough to know that at the end of the day, you have to weigh all factors into the results. The original question from the man who started the thread was "do low numbers on extreme spread & standard deviation always correlate to the smallest group?" My answer to that is, Low ES/SD is important and only one factor in loading and competing but does not in its self correlate to the smallest group.

These are F-open only results for that day.
Southern Indiana Rifle & Pistol Club
Mid-Range Prone & F-Class Match Results Match Date 10/12/19

2 FO HM Plant Brad 199 15 199 10 199 11 597 36
3 FO HM Draggoo Dwayne 197 7 198 10 197 8 592 25
4 FO HM Phillips Billy 195 7 198 4 199 9 592 20
1 FO HM Carroll James 196 8 184 2 193 3 573 13
2 FO MK Bradley Roger 188 2 191 6 188 4 567 12
3 FO UM Ohlmann Mike 189 5 184 2 187 3 560 10
4 FO MA Bray Tom 180 2 179 4 186 1 545 7

Here are two of my targets from Dead-Zero at 1000yd f-open. I forgot to capture relay 1. It sure looks like SD/ES plays a part. Shot 7 on the second target was much slower than rest. It sure changed the group.

 

To be quite honest when I get a low shot like that one in the last picture that case will never be loaded again. It usually doesn’t make it home. Seriously. It might not be the case, but it might be. That case cost you $1 (probably the same price as firing that case once). But is it really worth the effort and cost to shoot it again and have it happen again. Neck tension / case capacity etc. might be off.

Just toss it

I have a great batch of 6mm cases that I use for mid range matches.. they all have 25+ firings on them. There is 83 cases left from that one box of 100 and I haven’t thrown one away in a long while.

 

Or mark them to use for foulers. Every time I have a shot drop out or go high the target speed is off the others. Helps to diagnose if it was me or the load (case, primer, charge, or bullet). Before shooting on the Shotmarker I wasn't sure which it was.

 

When I change something such as powder, bullet temp, etc, I characterize my barrel.
Bear in mind , my guns have tuners installed.
I do a ladder test of 5 shot groups over a reasonable spread of loads. I shoot them round -robin style and find sd and ES and plot the curve vs load then do a 4 or 5th order curve fit. 5 shot groups done this wayyields excellant fit to 4th or 5th order curves so I am satisfied with my results.
By the way, this test finds the longitudinal resonance of the barrel. Once found, velocity distribution minimizes.
Then, I tune my tuner.

 

I always take those cases home for examination. If you don't, you might never figure out what was wrong /different about that case, which might allow you in the future to cull those cases BEFORE ever firing any low 9s.

 

So what have you all figured out to cause a flier in your examinations of culprit cases?