ES/SD vs Group Size

[TexAg08]

What does everyone base their load development on? Chase the best ES/SD or the best group size? Do they always turn out to be the same result? Which would be considered the most “accurate” way of determining a guns optimal load?

Example: I have a load that is single digit ES/SD, but the better grouping load has an ES/SD that is higher though within hunting specs (ES less than 25).

 

[wyosam]

Depends on the goal. Little tiny groups at shorter distance? ES doesn’t matter much if its shooting good. As the range gets longer, accuracy becomes more dependent on ES, so you have to chase both.


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[willfrye027]

You could run both situations in the MERC calculator and see what gives you a better hit %

Ex .3moa group with SD 10

vs

.75 moa group with SD 5

My guess is SD will matter more for making a hit on game...depending on how big of groups were talking

 

[TexAg08]

I am curious how shooter involvement can affect group size, where ES/SD are independent of the shooter.

Granted, a rifle and load will likely shoot differently, albeit minor, from shooter to shooter. I see chasing both to somewhere with a best of both scenarios, but from one weekend to the next, a group could change.

Oh the fun of chasing the perfect load. Just trying to remove as many variables as possible to better evaluate the data.

 

[TexAg08]

Example of results from today. Upper section is 1x fired brass and the lower is new brass of different lot, so I am evaluating them separately.

 

[willfrye027]

Example of results from today. Upper section is 1x fired brass and the lower is new brass of different lot, so I am evaluating them separately.

personally, I would be using the aggregate/total of all those shots to calculate SD/group size. Statistically that makes more sense and you get a more true value.

realistically your true group is about 1 MOA which is great for that many shots in a hunting gun.

now Calc SD based on all the shots (separate new vs old brass if you want). That’s a more realistic number

 

[TexAg08]

personally, I would be using the aggregate/total of all those shots to calculate SD/group size. Statistically that makes more sense and you get a more true value.

realistically your true group is about 1 MOA which is great for that many shots in a hunting gun.

now Calc SD based on all the shots (separate new vs old brass if you want). That’s a more realistic number

I couldn’t capture it on the screen shot, but each row related to a different charge weight. Normally I run 5 shot strings, but I have to let the barrel cool longer, and it’s getting close to our annual hunting trip, so trying to minimize brass usage on load development.

 

[willfrye027]

I couldn’t capture it on the screen shot, but each row related to a different charge weight. Normally I run 5 shot strings, but I have to let the barrel cool longer, and it’s getting close to our annual hunting trip, so trying to minimize brass usage on load development.

MERC - Maximum Effective Range Calculator

I recently created a Microsoft Excel based tool that calculates your probability of hitting a target. It allows study of the effects of rifle and environmental variables and uncertainties on hit percentage. Read below, and check out the screenshot to see what it’s all about. I am sharing this...

www.rokslide.com

This is what you need. It will answer the question for you. I see what you’re saying...1 in MOA with low SD vs small group with high SD. Try the calculator it’s pretty sweet.

My gut tells me that you need more data/more shots recorded to draw meaningful conclusions though. Especially if you’re looking for this detailed of an answer. Maybe pick a couple of the best contenders and shoot another 3-5 shots.

 

[tdhanses]

I personally focus on ES/SD, yet to have a load with single digit SD’s and ES under 20 shoot bad.

 

[ARMY_GREEN]

I watched a guy setup his LabRadar then he just shot the back stop, no target. I mentioned this to the guy that runs the place, this guy with the Labradar only comes there to check ES/SD, those numbers determine if the load might be something this guy wants to explore.

My Magnetospeed is used for FPS and ES / SD. I hate the idea that it is altering my barrel harmonics but that is how it goes.. I want that FPS with low ES / SD. The Grail

 

[TexAg08]

I watched a guy setup his LabRadar then he just shot the back stop, no target. I mentioned this to the guy that runs the place, this guy with the Labradar only comes there to check ES/SD, those numbers determine if the load might be something this guy wants to explore.

My Magnetospeed is used for FPS and ES / SD. I hate the idea that it is altering my barrel harmonics but that is how it goes.. I want that FPS with low ES / SD. The Grail

And that is my dilemma. I shot a group about a month ago at 200yds that was 0.65 MOA with acceptable ES/SD for hunting. Figured this trip to the range I would check it without the Magnetospeed to verify any POI shift. Well, that group ended up being the worst of the day. Put Magnetospeed back on to shoot remaining loads to check speeds and they tightened back up. So was it due to shooter variance, Magnetospeed, or just time of day?

This is why I am debating on going with ES/SD and then shoot for groups without the chrono attached.

 

[N2TRKYS]

And that is my dilemma. I shot a group about a month ago at 200yds that was 0.65 MOA with acceptable ES/SD for hunting. Figured this trip to the range I would check it without the Magnetospeed to verify any POI shift. Well, that group ended up being the worst of the day. Put Magnetospeed back on to shoot remaining loads to check speeds and they tightened back up. So was it due to shooter variance, Magnetospeed, or just time of day?

This is why I am debating on going with ES/SD and then shoot for groups without the chrono attached.

Doesn’t something hanging off the end of your barrel jack up your barrel harmonics?

 

[ARMY_GREEN]

And that is my dilemma. I shot a group about a month ago at 200yds that was 0.65 MOA with acceptable ES/SD for hunting. Figured this trip to the range I would check it without the Magnetospeed to verify any POI shift. Well, that group ended up being the worst of the day. Put Magnetospeed back on to shoot remaining loads to check speeds and they tightened back up. So was it due to shooter variance, Magnetospeed, or just time of day?

This is why I am debating on going with ES/SD and then shoot for groups without the chrono attached.

I've considered the Gen III Magnetospeed Mount and the Wiser Precision Chrono Mount. I don't like the idea of the Magnetospeed and accessories nearing the cost of the Labradar. Do I just buckle down and buy the Labradar?
The Labradar has had a mix of opinions on SH and a good solid tripod is recommended over a table mount. The Labradar also works better with the After Market add on trigger like JKL Inertial Trigger or other as I've read.

I will probably buy the Wiser or ask my kids to get me the MK Machining version as a XMAS gift

 

[Dayv_33]

One thing I have always wondered is how ES and SD even change based on a different powder charge or load. I get how group sizes and/or POI can differ based on the harmonics or barrel timing of different loads but doesn’t it seem like ES and SD should be a function of the consistency of your load and always be low if enough attention is paid to the consistency of the powder charge, case prep, components, etc? I know that’s not what happens in real life in load development, just don’t understand why.

 

[TexAg08]

I've considered the Gen III Magnetospeed Mount and the Wiser Precision Chrono Mount. I don't like the idea of the Magnetospeed and accessories nearing the cost of the Labradar. Do I just buckle down and buy the Labradar?
The Labradar has had a mix of opinions on SH and a good solid tripod is recommended over a table mount. The Labradar also works better with the After Market add on trigger like JKL Inertial Trigger or other as I've read.

I will probably buy the Wiser or ask my kids to get me the MK Machining version as a XMAS gift

I like the design of the Wiser, but I would have to further modify my factory stock to make it work. (Mount a pic rail on one side of a super flex stock) or I could just backup and buy a XLR or KRG chassis.

I thought about the LabRadar, but at the time cost played some factor. The other thing was that I always shoot at public ranges and didn’t want to deal with false triggers.

 

[tdhanses]

I watched a guy setup his LabRadar then he just shot the back stop, no target. I mentioned this to the guy that runs the place, this guy with the Labradar only comes there to check ES/SD, those numbers determine if the load might be something this guy wants to explore.

My Magnetospeed is used for FPS and ES / SD. I hate the idea that it is altering my barrel harmonics but that is how it goes.. I want that FPS with low ES / SD. The Grail

I do the same as that guy, I just do it with the magnetospeed. No need to shoot at a target when you don’t care how the groups look, backstop is a backstop.

 

[tdhanses]

And that is my dilemma. I shot a group about a month ago at 200yds that was 0.65 MOA with acceptable ES/SD for hunting. Figured this trip to the range I would check it without the Magnetospeed to verify any POI shift. Well, that group ended up being the worst of the day. Put Magnetospeed back on to shoot remaining loads to check speeds and they tightened back up. So was it due to shooter variance, Magnetospeed, or just time of day?

This is why I am debating on going with ES/SD and then shoot for groups without the chrono attached.

I never shoot for groups with it on, just go for ES/SD and to get a baseline avg ft/s.

 

[tdhanses]

One thing I have always wondered is how ES and SD even change based on a different powder charge or load. I get how group sizes and/or POI can differ based on the harmonics or barrel timing of different loads but doesn’t it seem like ES and SD should be a function of the consistency of your load and always be low if enough attention is paid to the consistency of the powder charge, case prep, components, etc? I know that’s not what happens in real life in load development, just don’t understand why.

Your not taking into account bullet seating depth and pressure, this can make a big diff in a load. ES/SD can easily change based on the seating depth. But once dialed mine are very consistent.

 

[T28w]

Your not taking into account bullet seating depth and pressure, this can make a big diff in a load. ES/SD can easily change based on the seating depth. But once dialed mine are very consistent.

So would you say that a more consistent seating depth and powder weight is why handloads tend to have lower es/sd than factory loads. I was surprised when I saw some charts of factory loads and how much es/ sd was present.

 

[tdhanses]

So would you say that a more consistent seating depth and powder weight is why handloads tend to have lower es/sd than factory loads. I was surprised when I saw some charts of factory loads and how much es/ sd was present.

I would say it comes down to many variables we control that are not a one size fits all approach, factory ammo can be extremely good, just never know if it’ll be good for your rifle. Also factory loads usually are not loaded with their optimal powder charge. One doesn’t have to reload but reloading does allow you to fine tune everything.