Load testing using only SD/ES numbers?

[Thisguy65]

Hey everyone, I was recently turned on to a new way (new to me atleast) of doing a load development. Wanted to see if anyone else has done it and their thoughts.

***I've attached a screen shot of the excel sheet***

Load up 5 rounds over the course of set Min-Max charge weight. Loading in .2/.3 grains.
Shoot over chronograph (Magnetospeed in my case)
Plot the data on to a excel sheet and see where the data kinda flat spots (there's the node). Also pay alot of attention to the ES/SD's as the low ES/SD is what you are looking for.

After a node is set load in .1 increments .2 up and below the node. Shoot 10 rounds and record the information. This test just confirms the data in the excell sheet.

Then once the charge weight is found, it's time to play with the seating depth.

I jumped around randomly choosing the cartridge and waiting 2 mins between shots. Barrel wasn't even really warm when I check it, so 2min is over kill.

Then I went all nerd and graphed the velocities that I recorded over a magnetospeed as well as the ES/SD. Steve at 6.5guys is the one I got the excel sheet/idea from. I downloaded his and put my information in, so prop goes to him. It honestly makes things alot easier to see for sure. 42.1 and 42.3 has a wide note it appears. However my velocity is not where I want it to be at. Then at 42.7 and 43.1 show low ES/SD as well how ever they are not in a wide node. My concern is temperature effecting the rounds so that they shoot (have high SD/ES) like the charge weights on each side of them. Basically if it got down to 40 degrees, the temperature would effectively lower my charge weight from 42.7 to 42.5. However it's just a theory, only one way to test the idea.

Since the barrel is still new, I'll load up 42.1 42.2 and 42.3 in 10 rounds and shoot those to see how the SD/ES are. Whatever the winners is of that one, load up 5 rounds at different seating depths.

The two charge weights that got chopped off at 42.9 (top) and 41.9 (bottom)

 

[BenPerfected]

Why be concerned about 50-100 FPS in velocity? Isn't accuracy the goal?
Ben

 

[Thisguy65]

Why be concerned about 50-100 FPS in velocity? Isn't accuracy the goal?
Ben

Can't you tighten/tune the group up with seating depth? Shooting these out to 1,000-1,200 in matches.

 

[Brians356]

Can you explain what you mean by "flat spot"? You mean where velocity doesn't change much? Or vertical location of group centers don't shift much? Or vertical spread of a groups are small (flat shaped)? Disambiguate, please.

 

[Thisguy65]

Can you explain what you mean by "flat spot"? You mean where velocity doesn't change much? Or vertical location of group centers don't shift much? Or vertical spread of a groups are small (flat shaped)? Disambiguate, please.

Where velocity does not change much as the grain is increased.

 

[STOMP442]

If the 42.7gr load is repeatable that's the one I would go with and call it good.

 

[Thisguy65]

If the 42.7gr load is repeatable that's the one I would go with and call it good.

Why is that stomp? Because of shear velocity? What I'm trying to understand is why guys pick what they pick, the reasoning behind it.

 

[SG4247]

I really like the data. But I'm kinda an excel junkie!

42.7, 42.8, 42.9 somewhere in there looks like the sweet spot to me. Where the mean and median are similar, even though the load varies slightly, seems like a good place to be.

Basically I am looking at where the slope of the MV curve is near zero.

Very interesting, thanks for sharing

 

[Thisguy65]

I really like the data. But I'm kinda an excel junkie!

42.7, 42.8, 42.9 somewhere in there looks like the sweet spot to me. Where the mean and median are similar, even though the load varies slightly, seems like a good place to be.

Basically I am looking at where the slope of the MV curve is near zero.

Very interesting, thanks for sharing

Why I'm looking at 42.2 is because if you look at 42.1-42.5 you'll see that graph tips down. It's not linear as seen in grains less than 42.2 and more than 42.5. You then see another dip around 43.1-2 mark and after words the linear line picks back up. Basically when the graph dips down and the velocity is really not increasing, that's the node area. At least from what I'm told stand point.

 

[savagedasher]

42.3 look the best to me. I see wind condition but not vertical. I would like to see 3- 2 shot target with the 42.3 and three more at 42.7. That will take the conditions out of the target 42.3 shows less vertical.
Larry

 

[SG4247]

I really like the data. But I'm kinda an excel junkie!

42.7, 42.8, 42.9 somewhere in there looks like the sweet spot to me. Where the mean and median are similar, even though the load varies slightly, seems like a good place to be.

Basically I am looking at where the slope of the MV curve is near zero.

Very interesting, thanks for sharing

Why I'm looking at 42.2 is because if you look at 42.1-42.5 you'll see that graph tips down. It's not linear as seen in grains less than 42.2 and more than 42.5. You then see another dip around 43.1-2 mark and after words the linear line picks back up. Basically when the graph dips down and the velocity is really not increasing, that's the node area. At least from what I'm told stand point.

I would also load 42.2 and 42.3 just for fun and see how they compare to 42.7, 42.8 and 42.9. If you look at your data for 42.7 & 42.9 you see only one high flyer out of 10 shots at 2836. If your brass wasn't sorted well or maybe the charge was a little heavy? The other 9 shots are really great statistically. You can practically draw a horizontal line through the mean for 42.7 and 42.9 as is. Don't let the excel generated trend line throw you off. Go shoot those and let the targets tell you what's best. Like to see those results!

 

[STOMP442]

I didn't even look at velocity I just think that it shot the best and had the best/tightest looking group. I could care less about velocity as long as it shoots great. a slow hit is better than a fast miss any day.

 

[Mozella]

Velocity is nice and a low SD is nice too. However, small groups are what I'm after. Take a look at a recent batch of sub 1/2 MOA 5 shot groups at 100 yards made with my 6mm BR Norma. The graph shows MOA vs SD along with a trend line showing a slight bias toward higher SDs giving better accuracy; just the opposite from what one might expect. I'd be interested in seeing how your SDs compare with your MOA.

The chart is a little hard to see and I'm not sure how to display it larger. But if you click on it, you can see it larger and read the numbers better.

MOA vs SD

 

[amlevin]

I hate to say it but 5 shots aren't enough for any statistical significance.

Yesterday I chronographed a load I deemed "near perfect" for accuracy. Shots one through 5 showed an SD of 14. When I finished firing all 25 rounds the SD was 9.5 with a Mean Absolute Deviation of less than 7.

The group sizes at 200 yards were just over .25 MOA. If I'd discarded that load just because of the higher SD after 5 rounds I'd be missing out on an extremely accurate load.

BTW, this is with a "Tactical Rifle" resting on a bipod and rear monopod, not a BR rifle shot in free recoil.

 

[Thisguy65]

I hate to say it but 5 shots aren't enough for any statistical significance.

Yesterday I chronographed a load I deemed "near perfect" for accuracy. Shots one through 5 showed an SD of 14. When I finished firing all 25 rounds the SD was 9.5 with a Mean Absolute Deviation of less than 7.

The group sizes at 200 yards were just over .25 MOA. If I'd discarded that load just because of the higher SD after 5 rounds I'd be missing out on an extremely accurate load.

BTW, this is with a "Tactical Rifle" resting on a bipod and rear monopod, not a BR rifle shot in free recoil.

I'm shooting the same setup as you minus off a rear bag. These 5 shots are just to see in to the window, so to speak. Next test is to load 10-15 rounds each to see is happening in those set of weight charges, long term.

 

[Marksman63]

Nice graphics. If they match Eric Cortina's thoughts would be great!

 

[savagedasher]

I hate to say it but 5 shots aren't enough for any statistical significance.

Yesterday I chronographed a load I deemed "near perfect" for accuracy. Shots one through 5 showed an SD of 14. When I finished firing all 25 rounds the SD was 9.5 with a Mean Absolute Deviation of less than 7.

The group sizes at 200 yards were just over .25 MOA. If I'd discarded that load just because of the higher SD after 5 rounds I'd be missing out on an extremely accurate load.

BTW, this is with a "Tactical Rifle" resting on a bipod and rear monopod, not a BR rifle shot in free recoil.

I'm shooting the same setup as you minus off a rear bag. These 5 shots are just to see in to the window, so to speak. Next test is to load 10-15 rounds each to see is happening in those set of weight charges, long term.

Just do 5- 2 shot then end result is the same. All it takes to get bad results is a condition change. No matter how you cut it after the second shot you can't make it better with more. If you average the total 10 shot by 5 you get the same results. If a condition make one bullet out The test is invalid With two shot you then can divide by 4 with some confidence in the results . Larry

 

[CharlieNC]

Defining a node based on lowest velocity sensitivity or variability does not necessarily mean that is also a node based on optimizing the harmonics associated with minimal poi shift with charge weight. Sometimes the node may agree, or not. Also there is a level of statistical significance associated with any sample size (not necessarily a high % of significance) and the level of variability also plays a major role.

 

[Thisguy65]

Velocity is nice and a low SD is nice too. However, small groups are what I'm after. Take a look at a recent batch of sub 1/2 MOA 5 shot groups at 100 yards made with my 6mm BR Norma. The graph shows MOA vs SD along with a trend line showing a slight bias toward higher SDs giving better accuracy; just the opposite from what one might expect. I'd be interested in seeing how your SDs compare with your MOA.

The chart is a little hard to see and I'm not sure how to display it larger. But if you click on it, you can see it larger and read the numbers better.

MOA vs SD

having consistent ammo who perform nearly the same each shot seems like that be more important, however seating depth would tighten up the group up more. At least this is my understanding.

 

[R.Morehouse]

How about speed sorting your brass to stay with in an acceptable to you window. It works....