What is considered a good SD and ES?

[CanPopper]

Today was the second time I've used my chrony so I don't have much experience with what is considered a good standard deviation and extreme spread for a load.

I tested three loads that shoot sub 0.5 MOA in my 300 Win Mag and got the following results:

185 Lapua Scenar - ES = 66, SD = 21
180 Hornady SST - ES = 61, SD = 22
220 SMK - ES = 67, SD = 27

Are these numbers considered decent, good, or mediocre?

 

[Lindy]

Re: What is considered a good SD and ES?

Ideally, one would like to have an SD not much more than the low teens.

You didn't mention how many rounds of each load you measured.

ES may not be a very useful figure of merit. You might find this interesting reading:

Chronograph Statistics

 

[CanPopper]

Re: What is considered a good SD and ES?

I shot 10 rounds of each to get the above results. (still reading your link)

 

[4Rail_Gunner]

Re: What is considered a good SD and ES?

A quote from Glen Zediker in his book "Handloading for Competition"

"The SD Quiz
Four choices: 3, 6, 12, 24, all conveniently doubles. My answers included.
1. Does a 3 shoot better than a 6? Ha. No.
2. Does a 3 shoot better than a 12? Hmm. Maybe. Depends on where that 12 came from, and when it's coming back.
Does a 3 shoot better than a 24? Dunno. Never shot with a 24. "

A thing to ponder is what are you doing with this gun? Hunting only or Match Rifle?
I agree that an SD in the low teens is ideal.

 

[Victor N TN]

Re: What is considered a good SD and ES?

In the 20s is OK for 100 yard hunting. But for serious competition I want an SD of 15 or less. Most of my benchrest loads are in the Standard Deviation of 8 area.

One other thing to think about. What chronograph are you using? I had 2 Shooting Chonys. They just read whatever they wanted. I sold 1 and gave the other to my brother. Right now I have an OLD Pact (my 4th chronograph) that I've been using for a long time. Shot side by side with an Oehler 35 it was less than 2% off at any time or group.

When I sign for my retirement next year I'm planning for possibly a CED millinium. Something I can download directly to my PC. And it has to be accurate.

Try prepping your brass a little more consistant. Also throw your powder charges very slowly and deliberately. I can usually get +/- 0.1 of a grain with my Harrell's Premium powder measure. For 1K targets I sometimes throw light and use a dribbler to zero out.

 

[doc76251]

Re: What is considered a good SD and ES?

When dealing with chronographs it would serve one well to remember what the "acceptable error" is for that particular chronograph. Even a .5% error will result in an error band of 13.5 fps with a bullet traveling at 2700 fps.

I consider any SD less than 10fps suspect. Preferred but suspect.

Cheers,

Doc

 

[MitchAlsup]

Re: What is considered a good SD and ES?

I agree with the above.

Never seen a SD lower than 15 when you count 50 cartriges from that load group.

For long range shooting (1000 yards) a 1 MPH error in the wind call is about equal to a 15 fps SD in the MV. {Or was that a 2 MPH error in the wind call? dangit forgot}.

In any event getting into the low teens for small numbers of rounds means your reloading procedures are dowing quite well. Getting below 10 fps is very very difficult.

 

[Short-bus]

Re: What is considered a good SD and ES?

I was out on Sunday and chrono's my loads, my greatest ES was 43 and that was the first group of the day from a CCB, next was 10.6, 27, 19, and 26. The 10.6fps ES was my pet load that I have suspected for a while now was "THE" load.

I would stick with trying to get the ES down to 25 or less, in the teens for more precise shooting at the longer distances.

Branden

 

[Lindy]

Re: What is considered a good SD and ES?

You may be confusing SD and ES. If you're not, you need to read this reference, because you appear to be paying far more attention to ES than you should. The ES - the correct term is "range" - of a fairly small number of rounds is pretty much meaningless.

Chronograph Statistics

 

[daxromana]

Re: What is considered a good SD and ES?

Lindy,

Thanks for that link. The article cleared up some misconception that I had about EV.

 

[Lindy]

Re: What is considered a good SD and ES?

You're quite welcome. It's a useful article for anyone who owns a chronograph. I had a copy of that article on my web site for a time when the site which originally hosted it went defunct. I entitled the link "Crimes with Chronographs".