ES/SD Goals

[jhord]

When it comes to ES and SD, what is a good realistic goal to strive for? With all the tricks I have learned here, I'm getting about 7 ES and 4 SD on my 6BR. Is that good, bad, or middle of the road? I've just started using a chrono in the past month, so I'm curious what I "should" be seeing.

 

[Chuckhunter]

If your getting single digit Es and Sd's, stay put, they are extremely low, however with that being said, if that load doesn't group well or meet your velocity requirements, you might still have to return to the drawing board.

 

[RonAKA]

You must have a good chronograph. I think that your SD and ES is well beyond that of the typical chronograph error alone, without considering the bullet speed variation.

 

[jhord]

I don't think my chrono is anything out of the ordinary, it is the Competition Electronics ProChrono. It seems to work without a hitch, or should I not trust it's data? I do get much different results with my .308 and .223. Those are nowhere near as good as my 6BR, even with the same attention paid to cartridge prep. "On target" my 6BR's vertical dispersion is probably .25 MOA or less, so that seems to agree with the chrono? The ES/SD #'s I gave are for my pet loads, there have been other trial and error loads double that. In any case, sounds like I'm on the right track?

 

[RonAKA]

It sounds really good to me. I'm not familiar with your chronograph, but it must be good. They cannot fail in a manner to give you artificially low SD and ES. It will always be the other way, unless somehow there is an error in the calculation.

As a comparison have a look at German Salazar's small rifle primer test article. Your numbers I would suggest are better than any of the primers he tested in a 6BR.

Small Rifle Primer Study

I use an Alpha Master and I do not get numbers close to that. The chronograph frequently gives me numbers that are simply not possible. I don't even bother to calculate SD or ES, except after the fact and only after conditioning the data (throwing out the Russian Judge scores). I only use the instrument to give me averages and I don't consider them valid unless I'm getting 10 readings or so minimum to average.

 

[Erik Cortina]

When it comes to ES and SD, what is a good realistic goal to strive for? With all the tricks I have learned here, I'm getting about 7 ES and 4 SD on my 6BR. Is that good, bad, or middle of the road? I've just started using a chrono in the past month, so I'm curious what I "should" be seeing.

How many shots?

You say .25 MOA, at what distance?

How fast are your bullets going?

What is the farthest distance that you are planning to shoot?

I agree with ChuckHunter, the numbers look good, but only if they group.

 

[jhord]

I'll keep gathering more data and see how it looks after a while. Usually, given enough time, I find ways to screw things up. ;D My .308 results are much more in line with what is shown in German's large rifle primer test. Maybe my chrono is a dud, I don't know... it does seem to give me more than a few "duplicate" readings.

@ Erik- Lately I have been doing all my shooting at just a touch under 700 yards. That's the distance from my barn door to the berm in my woods. 107SMK's are flying about 2835 with 30.5 Varget, 95VLD's are going about 2950 with 30.8 Varget. (going off memory, notes are in the shop) Lapua brass, BR4 primers. 30 jump on the 107's and 20 jump on the Bergers. When I jam the Bergers the ES/SD go to pot, and so do the groups. I am shooting 5 shot groups, to practice for benchrest.

 

[Erik Cortina]

It all sounds good then! ;D

 

[Chuckhunter]

Jhord, it does sound as though you have a very good load going there. If you are pleased with the way it groups, shoot a string of about 20 shots, taking your time so the barrel doesn't overheat, this will give you more viable data. I suspect your numbers will rise slightly but if your SD stays in the single digits, you probably have a winner. Good Luck and good shooting.

 

[artbosco]

When it comes to ES and SD, what is a good realistic goal to strive for? With all the tricks I have learned here, I'm getting about 7 ES and 4 SD on my 6BR. Is that good, bad, or middle of the road? I've just started using a chrono in the past month, so I'm curious what I "should" be seeing.

Do yourself a big favor. Forget about ESs and SDs. Work up your load with the object of putting bullets through the same hole. Once you've done that you've reached the ultimate goal. Then, if you're curious, see what the speed is with a chronograph and what the ES and SD is.

You don't back into the most accurate load with ES, SD, or a Chrono. You do it straight on with powder, seating depth, and neck tension. A lot of us in short range "B"enchrest couldn't tell you what the ES, SD, or speed of our bullets are achieving, but we can show you targets where bullets are producing groups in the zeros and teens and explain how we got there with powder, seating depth and neck tension.

Watch this for some interesting and parallel ideas: http://www.youtube.com/view_play_list?p=7D85822FD9E41FF2

 

[jhord]

Understood, thanks for the input. I guess that's pretty much what I have done so far, I worked up the 2 loads mentioned above by tinkering and observing the target. I bought the chrono more or less to see what bullet speeds were so I could use ballistics programs more effectively. But the ES/SD data got my curiosity, now I can perhaps revisit some loads to see why they didn't shoot well and see what is going on. For example, Berger 105VLD's would not group well, but I never tried jumping them. After seeing what happened with the 95VLD's when I tested jump vs. jam over the chrono, now I think I need to go back and mess with the 105's again. Etc.

Do yourself a big favor. Forget about ESs and SDs. Work up your load with the object of putting bullets through the same hole. Once you've done that you've reached the ultimate goal. Then, if you're curious, see what the speed is with a chronograph and what the ES and SD is.