Which should i use SD or ES

[FamilyMan]

I am running a little test tomorrow at the range
I have 50 once fired brass that I prepped exactly the same except I neck tired half of them just taking down the high spots to where about 80-90% has been cleaned up. So my plan is to fire 4-5shot groups of each type to see if neck turning really makes a difference so my thought was using my Magneto Speed chrono is test the consistency and accuracy of each group but should I using SD or ES to compare them? Or should use something else? Obviously I will be comparing grouping down range but anything else?
Thanks in advance this is my first go at something like this.
If it is if any importance I am firing 6.5CM with 41.5gr H4350 and 140Amax's and 26" Bartlein 1:8

 

[clmayfield]

Re: Which should i use SD or ES

The best metric would be SD for all 20 shots of each set.

If you can keep track, you might also try to randomize which group gets shot when.

In other words, shoot 1 group turned, 2 groups unturned, 1 group turned, 1 group unturned, 2 groups turned, 1 group unturned. Or even better yet, shoot the groups round robin.

 

[TheRedHorseman]

Re: Which should i use SD or ES

SD with a q test to identify outliers that can be omitted.

Or if you don't feel like playing statistics games, just stick with SD. Super easy if you plug it into a spreadsheet.

 

[1SMALLJOHNSON]

Re: Which should i use SD or ES

Great to see FamilyMan having some fun with all this. Good for you. My only added comment might be for you to take a look at Taguchi Matricies. Sounds overly complicated, but actually quite simple. It's just that there's a bunch of geeks who use it, and find humor in making it sound overly complicated. Makes them more self-important if they make it sound like us "normal" people don't understand them. They're just so much smarter than us, afterall...

So, what you do is figure out how many variables you've got. Next, decide the "on and off" measurements for those variables.

Now, a matrix is basically a series of rows and columns. Think about one side of a rubix cube. You got 3 rows and 3 columns. With other matricies, you can have 2x2, 3x3, 4x4, all the way. Matters not. The way you add a third variable is to turn that variable on and off, while (sort of) keeping all other variables constant. The cool thing about Taguchi is that you're actually testing that third variable, while ALSO varying the other two.

Why's it beneficial??? Let's say you have 3 variables you want to test. With your matrix, that would work out to 3 columns and 3 rows. 3x3 = 9. So, you'd have to run 9 tests to see every affect from those variables. But with Taguchi, and a little bit of smarts, you can test all those variables (with a good degree of confidence) in only 5 tests. Saves you time.

I won't go into all the nuances of Taguchi, but simply say that you can find easy examples all across the internet. Just search the term "Taguchi matrix". Don't pay attention to the egg-heads who want to loose you in the details. Just shows that they're incapable of communication. Look for a 3x3 example, and work it out on paper with the example provided. Light will dawn quickly, and you'll enjoy the process!

Good shooting!

 

[Greg Langelius *]

Re: Which should i use SD or ES

I have very basic core doubts about any Chrono-derived data that deals in differences of less than 3 digits.

I would suggest that when you do your firing, you make marksmanship your most important effort.

While I respect your desire for numeric data, I still believe that the most important measure of a load's performance is its measurable accuracy (i.e. how far, on average, does the POI fall from the group's center.). That's the really important number in all of this.

Greg

 

[clmayfield]

Re: Which should i use SD or ES

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Langelius *</div><div class="ubbcode-body">
While I respect your desire for numeric data, I still believe that the most important measure of a load's performance is its measurable accuracy (i.e. how far, on average, does the POI fall from the group's center.). That's the really important number in all of this.

Greg</div></div>

True. But you can use a ballistic calculator with chrony data to determine what slow and fast shots would look like vertically at 1,000 yards away.

But the point is well taken that one might try to measure all of this at long range. The problem with folks like me is that I have to drive 2 1/2 hours to my 1,000 yard range whereas my short range is 30 minutes away, so it is easier to try to judge these things at the short range with groups and chrono data.

Maybe that is an issue for the OP and maybe not.

 

[armorpl8chikn]

Re: Which should i use SD or ES

I am with Greg on this one. Beyond that...

I take my best group at 300yds with the lowest SD. That is my best load for long range.

 

[Boogaloo]

Re: Which should i use SD or ES

I read that relying on SD for 5 or 10 shot strings is fairly useless. You need much more data (shots in a string) for SD to become a valuable data point. ES (for me) is far easier to interpret since everything else falls between the fastest and slowest shot (obviously), so the lower the ES (observed), the more consistent the load is. Presumably, if you have a low ES, then your bullets should all fly pretty much the same arc as long as the conditions (wind etc) are not swinging wildly on the day.

I am fairly new here, and this is just my opinion, so please don't take my reply as a challenge to anyone else' method here. This is just what seems to work for me. Admittedly, I am nowhere near a capable 1000 yard shot guy yet.

 

[FamilyMan]

Re: Which should i use SD or ES

Well I am going to have to agree with Greg on the skepticism of the reliability of a chrono's data on the sheer fact that it was working great with all my other loaded rounds today until I got ready to run these tests and the damn thing stopped working. Out of 40 shots fired it only red 3 of them accurately and even gave me 76 ft/sec on 2 others, now that's what you call sub sonic. Go figure it all works till you really need it to. In its defense it might of just been the cold cause the LCD screen was pretty slow most the day and it seems as the temperatures dropped a little towards the end of the day is when it stopped working and visibility was pretty bad all day being it was snowing for 90% of the time I was only able to catch glimpses of the 800-1000 yd targets for just small portions of the time. So I just rang steel most the day and never really shot for groups but I will load up a similar test group and head out again when some better weather comes around.
Thanks for the replies and Ill post the results when I get a chance to do it. Not that I think I'll find anything most y'all don't already know

 

[Greg Langelius *]

Re: Which should i use SD or ES

My skepticism is based on the manufacturers' own caveats. If you read the instructions completely, most of them will say somewhere in there that the displayed data has an error margin of +/-1% of the displayed value. For a 3000fps value, that means true velocity could be anywhere between 2970fps and 3030fps. Within such limits, ES/SD values smaller than 60fps are meaningless; and I suspect that the true uncertainty is probably even greater. When I have to deal with error factors using small data samples, I estimate reality by applying a 2X fudge factor.

Greg