Math Quiz...

[huntinghuasna]

Which load would be more accurate @ 750 yards?
(I don't know the answer, not going to mention rifle or load info.)

Bullet DiA. = 0.264", ~124/125 grain
Est. B.C. = G1 - 0.600 / G7 - 0.298

#1. 3/8 MOA at 100 yards with an extreme spread of 32fps, muzzle velocity of 2,904fps
or
#2. 7/8 MOA at 100 yards with an extreme spread of 8fps, muzzle velocity of 2,841fps

I'm sure this will be easy for some… I'm scratching my head after a day at the range. I'm wondering how much the ES could play on accuracy at this distance (10" steel plate).

 

[RegionRat]

At 750 yards, the linear answer is #1 shoots 0.675 MOA vertical and #2 shoots 0.975 MOA vertical

ETA: the contribution to vertical is the sum of the trajectory plus the original group dispersion.
The trajectory of case 1 due to the ES is only 0.3 MOA
The trajectory of case 2 due to the ES is only 0.1 MOA

However, you can't always assume their performance is linear.

 

[Mason Blackmon]

In theory number two will be more consistent since the FPS is more consistent.
However I've never had 30 fps make a much of a difference with anything I've done. And number 1 is faster by almost 100 fps which i would think is significant. I think it would have to take shots down range to actually come up with a true answer to you problem

 

[FEENIX]

Which load would be more accurate @ 750 yards?
(I don't know the answer, not going to mention rifle or load info.)

Bullet DiA. = 0.264", ~124/125 grain
Est. B.C. = G1 - 0.600 / G7 - 0.298

#1. 3/8 MOA at 100 yards with an extreme spread of 32fps, muzzle velocity of 2,904fps
or
#2. 7/8 MOA at 100 yards with an extreme spread of 8fps, muzzle velocity of 2,841fps

I'm sure this will be easy for some… I'm scratching my head after a day at the range. I'm wondering how much the ES could play on accuracy at this distance (10" steel plate).

When in doubt, shoot it 750Y; you need to figure out your dope anyway.

 

[Black Hat]

When in doubt, shoot it 750Y; you need to figure out your dope anyway.

Agreed, you can crunch as many numbers as you like but the proof is when you burn the powder at that distance.

 

[Bang4theBuck]

At 750 yards, the linear answer is #1 shoots 0.675 MOA vertical and #2 shoots 0.975 MOA vertical

ETA: the contribution to vertical is the sum of the trajectory plus the original group dispersion.
The trajectory of case 1 due to the ES is only 0.3 MOA
The trajectory of case 2 due to the ES is only 0.1 MOA

However, you can't always assume their performance is linear.

This is the definitive answer no doubt!

 

[Allen Lone wolf]

Gonna say #1 and you may be shooting a 7mm prc. Just a guess of course.

 

[Bang4theBuck]

Gonna say #1 and you may be shooting a 7mm prc. Just a guess of course.

My guess is this is a 6.5 CM. Bullets are too slow for a 7prc of that weight, or so it seems

 

[Allen Lone wolf]

My guess is this is a 6.5 CM. Bullets are too slow for a 7prc of that weight, or so it seems

You are probably right. Looked right past the bullet diameter

 

[DuckHunt]

Which load would be more accurate @ 750 yards?
(I don't know the answer, not going to mention rifle or load info.)

Bullet DiA. = 0.264", ~124/125 grain
Est. B.C. = G1 - 0.600 / G7 - 0.298

#1. 3/8 MOA at 100 yards with an extreme spread of 32fps, muzzle velocity of 2,904fps
or
#2. 7/8 MOA at 100 yards with an extreme spread of 8fps, muzzle velocity of 2,841fps

I'm sure this will be easy for some… I'm scratching my head after a day at the range. I'm wondering how much the ES could play on accuracy at this distance (10" steel plate).

WHERE is the Hall Monitor when we need one???

 

[med358-boise]

IMO, load 1 is theoretically more accurate. Again, the operative word is theoretically.

First, you would have to hold all other factors constant and equal with the two loads - for example the standard deviation of the velocity values has the exact same distribution and that both distributions are normal. Since, the preceding scenario is highly unlikely - this exercise is a bit of mental masturbation.

Given the above, the question is - does the difference in ES exceed all the other variables that generated a 3/8 MOA group vs. a 7/8 MOA group?

The difference between a 3/8 MOA group and 7/8 MOA group at 750 yards is 3.93 inches.

Then compare a zero variance in velocity for Load 2 and a max variance for Load 1. A difference of 32 fps at 750 yards for Load 1 is 3.3 inches which is less than 3.93.

Therefore, the answer is no - in theory.

If I was looking for something closer to a more accurate and practical answer. I would first shoot two 5 shot groups with each load on a calm day to see if I can put 8/10 for each load into a 10' circle at 750 yards. If that is a yes, we at least have some data that tends to eliminate shooter error. I would record these groups sizes.

Then I would shoot five 5 shot groups of each load. Now you have seven 5 shot groups for each load and a much better idea of the real answer.

 

[khmplus]

All of these evaluations are assuming the shooter is flawless.

 

[BrentM]

Look up wez by litz.

Generally the lower the sd and es the lower the dispersion if things are equal. Since your close range group 2 is not as accurate but lower es you may not see the dispersion until further out. Horizontal and vertical dispersion are the things we need to control best we can. Vertical dispersion is the ES and SD generally. Horizontal is often environmental, wind. Scatter dispersion is all things combined and Litz puts into a cone of accuracy for discussion.

I've had 150 fps es during load development that shot amazing groups at 500. That's my target range for load development generally. No matter the one time range session findings, I'll always shoot for low es and sd to reduce vertical dispersion and I target .5 moa accuracy at 500 plus. I also generally don't get excited about tight 100 yard groups unless they prove themselves at distance. Most people really believe that close accuracy is linear……

 

[Oak_Leaf]

IMO, an 8 fps spread giving 7/8 moa at 100 raises red flags since the vertical due to velocity spread is only 0.1 moa like someone mentioned. There's some ghosts in the machine at work. If we were in Vegas, I'd bet on #1.