ES and SD vs accuracy/group size??

[BgBmBoo]

OK...so again...I am not a pro. reloader. I have a question about accuracy and ES and SD #'s.

I am working on some .243 w/107 SMK's over H4350 loads. I have found a nice shooting load but the ES and SD #'s are not what I would call very good....avg. is 30-40's on ES and in mid to high teens on SD.

Now when I have really low ES...low teens and single digit SD #'s the groups are not good.

I will assume there is something I am doing that is causing this.
Today I was playing with seating depth and just wondering what the deal may be.

Take care,Stan

 

[Victor N TN]

Re: ES and SD vs accuracy/group size??

Stan,

I think you answered your own question. Sometimes...SOMETIMES the lowest numbers are not the best groups. Go by your vertical group size. As much as I have shot across the sky screens, there aren't numbers chiseled in stone anywhere that I try to get to. Yes, on longer range loads I TRY to get the SD as low as I can. But if it isn't printing it on the paper, it isn't going to be a good load, no matter what the numbers say. Chronographs are wonderful tools for figuring drop charts, repeating loads and other tests data. But the target tells the true tale.

Use your head for what it was meant for. I'm sure you'll come up with the right answers.

 

[esorensen]

Re: ES and SD vs accuracy/group size??

I usually find some real accurate loads that have ES/SD in the teens/ single digits. However, I worked up a load for .223 with TAC and CCI 450s and am looking at a couple of honest .5 MOA groups at 100 that have ES/SD in the 30s and teens. Its good info, but I just shoot what works. Those weren't real long range loads anyways.

I have however, worked up 105 Bergers in the .243 and am using Retumbo. I found the speed 3075 I think. H1000 gave WAY better ES/SD, but only 2875 I think. The Retumbo load will shoot excellent at 1000. If I were only shooting paper for scores, I would use the H1000. I use the Retumbo as a hunting load so I prefer the extra speed.

 

[KYpatriot]

Re: ES and SD vs accuracy/group size??

Stan,

Are you POSITIVE that the only difference between the groups are the higher ES/SD?

The results just dont make sense. The more consistent the ammo, the more consistent the results if ALL other things are equal. I think something else is going on that is overshadowing the ES data making it irrevelent to the group size, in the same way that gusty winds or unstable shooting position can overshadow a known good load.

Maybe you could try again and shoot several groups, round-robin style, timing between shots for barrel cooling, focusing on the exact same hold, etc in other words taking every possible variable out of the equation.

Also, if you are near an OCW node for your rifle, the ES may not be impacting your groups much as the small difference in velocity, whether they are a result of inconsistent reloads or temperature variation from day to day, will be negligible. That is the whole point of the OCW method. If so, the group variation is almost certainly due to something else and not your velocity/ES. This is a good thing, whether it was on purpose or not.

Good luck, let us know how it works out.

 

[BgBmBoo]

Re: ES and SD vs accuracy/group size??

Hey KY.
I am with you. I feel the low ES and SD #'s should be the ticket. I try my very best to remove ALL neg. influences when I am shooting for groups and load work. By that I mean I shoot off a concrete bench. Use a bag plate on the forend of my rifle so it is square in my front rest (JJ machine), use a good solid rear bag filled with heavy sand, have my trigger adjusted to about 6-8 oz. (Jewell) and shoot bench rest style with not any part of my body touching the rifle. It is a pretty solid setup.
Oh...and I use a portable fan and keep it on the barrel and try and give a full 2 min. between shots.

The only variable that is in the mix from my first group shooting and this last set was a different range. The first range was at 818' elevation and the last range was at 4200' elevation.
Not sure if that would effect SD and ES #'s and groups or not? The point of impact was the same.

Anyways...I will try some more groups with the load/seating depth that gave me the lowest #'s and see what is what.

Thanks for the input and Happy 4th!!

Take care,Stan