# Hit percentage analysis

#### BryanLitz

Awesome article on the PRS blog! Explains how Weapon Employment Zone (WEZ) analysis can be used to determine your hit percentage for a range of variables.

How much do you think your hit percentage on a 10" plate improves at 700 yards if you improve your rifle's 100 yard groups from 0.5 MOA to 0.1 MOA? Read and you may be surprised:
Applied Ballistics | PrecisionRifleBlog.com

-Bryan

#### cohunter14

##### Well-Known Member
Thanks for sharing that Bryan, great info.

#### pfxn

##### New Member
Hey Bryan,

Good article. As someone with an engineering background it's always really interesting to see competent and concrete analysis such as this to help the practical shooter gauge what's really important for putting rounds on target and what's just beating your head against the wall. Really good stuff.

I have a question though about how you're using uncertainty in the monte carlo. It looks like for most of your variables you're asking the user to specify the uncertainty as 1 standard deviation. After all most all of our chronographs will tell us up front the standard deviation of muzzle velocity for a string of shots. I assume this means internally you use a gaussian random number generator to pick a random error for each shot.
How do you handle the random dispersion associated with rifle precision? I see the header for that box is "extreme spread". Are you still using a gaussian distribution but interpreting the extreme spread as 2 or 3 sigma? If so, which? If I remember from stats class about 68% of my shots should group into 1 sigma of deviation, 95% into 2 sigma, and 99.7% or so in 3 sigma.

I think the average shooter is likely to shoot 3 - 5 shot groups to gauge their rifle precision, and it's common to dismiss flyers ( "I guess I just flinched on that one"). If I was to go to the range tomorrow and shoot 100 rounds on paper and carefully record them all, how should I best determine extreme spread for use with your software?

#### BryanLitz

very good question!

The answer is that we divide the user input for 'rifle groups' by 4, and use that as the standard deviation of that parameter. By dividing by 4, we're capturing +/- 2 SD's, which is 95%, or 19/20. Seeing as how most shot groups are under 20 shots, 95% is essentially 100% for 3 or 5 shot groups.

This was done to ease misuse of the interface. Shooters don't know the SD of their groups, but they do know CTC. It's been argued that we should handle the other input parameters the same way, which might be better than how we have it now.

The tool's gotta work for everyone; Joe average gets the same interface as an engineer which is a challenging part of creating a tool with mass appeal. I think the very nature of this tool sort of limits its user base as you gotta be somewhat of an egg-head to think it's interesting to begin with.

-Bryan

#### cohunter14

##### Well-Known Member
Bryan, one question for you even though I know you weren't the one who wrote that blog post...if they were to take the 10" target and run numbers out to 1,000 yards instead of 700, would the group size matter more at that point? I have to assume that at some point, .5 MOA versus 1.0 MOA makes a difference, especially at longer distances with smaller targets. I'm guessing the writer chose those distances and target sizes to illustrate his point the best?

#### CB11WYO

##### Well-Known Member
Absolutely wonderful article/software! Confirmed an inkling I've had kickin' around between my ears for a while now.

#### CB11WYO

##### Well-Known Member
Bryan, one question for you even though I know you weren't the one who wrote that blog post...if they were to take the 10" target and run numbers out to 1,000 yards instead of 700, would the group size matter more at that point? I have to assume that at some point, .5 MOA versus 1.0 MOA makes a difference, especially at longer distances with smaller targets. I'm guessing the writer chose those distances and target sizes to illustrate his point the best?

Cohunter,
To my way of thinking... your rifle's grouping capability DOES become more of a factor when the size of the target/kill zone becomes SMALLER than the rifle's grouping ability at "X" distance. For instance a 1 MOA rifle trying to hit a 1/2 MOA gong at long range would have lower percentages than a scenario where the rifle's capability is tighter than the intended target's size, again at "X" distance.

my .02 anywho...

Wow, that was clear as mud

So basically if I were new to LR and building a new rifle...
I would look at the size of the intended target/kill zone at the max distance I would like to shoot/kill it at and then build my rifle to be able to shoot groups equal to or smaller MOA-wise than that, then spend the rest of my energy mastering wind reading, shooting techniques, etc... Whether I'm shooting steel, milk jugs, X-rings, deer vitals, or the broad-sides of barns lol

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#### cowboy

##### Well-Known Member
Absolutely wonderful article/software! Confirmed an inkling I've had kickin' around between my ears for a while now.

Agreed - it took me a long time to quit chasing the one hole groups and get my rear end out and just shoot more in the wind.

Bottom line for me is: more trigger time and trying to become a better "wind whisperer" has had way more benefits than trying to improve on a 1/2 or 3/4 MOA load combination.

##### Well-Known Member
Bryan,

Thanks for posting the article. Uncertainty analysis should be at the top of the list for tools of use especially when time, resources, and first round hit probability are all too often associated with hunting decisions.

One note of observation, the article didn’t indicate the atmospheric parameters for the analysis. Running analysis with most likely to common hunting conditions and using same uncertainty as the article the percentage difference between 1 MOA and .5 MOA at 700 yards were more in tune of 10% difference. Analysis between .5 MOA and .1 MOA were in line with the article. The article as is could tend one to believe there is little difference between a 1 MOA and a .5 MOA producing gun/ammo/shooter combination when in most likely situations I don’t believe this to be the case.

Thanks much for a great WEZ product. An investment with the program has been worth every penny.

##### Well-Known Member
Absolutely wonderful article/software!
Agreed.

If faced to make a choice between aTerrapin and uncertainty analysis I’d dump the Terrapin in a heartbeat. IT’S THAT IMPORTANT! Why? Two fold. First, as mentioned in the article, WEZ allows one to examine percentage difference with a change in input. When does one stop chasing precision in favor of accuracy? Where are time and resources best utilized for maximum return? WEZ provides comparison in terms of hit percentage return. Second and most important falls in line with the nature of this forum. WEZ allows one to annotate most likely hunting condition cold bore first round hit percentages onto range cards. A hunter can use this information to hunt percentages in lieu of fixating on a set range. For example, if a hunter has determined they will not risk taking a shot with less than 90% assurance of striking vitals, WEZ is capable of this analysis. An egg-headed person who is into “this stuff” will have already figured out how to do this by the time they complete reading the post. For the rest, it would be great if an article could be linked on how to do this...hint…hint. Fixating on shooting percentages rather than range is a tremendous advantage with this type of program and worth every penny. BTW, I’m glad I don’t have to make the decision to dump my range finder. Let’s hope that day never comes!

#### cohunter14

##### Well-Known Member
Cohunter,
To my way of thinking... your rifle's grouping capability DOES become more of a factor when the size of the target/kill zone becomes SMALLER than the rifle's grouping ability at "X" distance. For instance a 1 MOA rifle trying to hit a 1/2 MOA gong at long range would have lower percentages than a scenario where the rifle's capability is tighter than the intended target's size, again at "X" distance.

my .02 anywho...

Wow, that was clear as mud

So basically if I were new to LR and building a new rifle...
I would look at the size of the intended target/kill zone at the max distance I would like to shoot/kill it at and then build my rifle to be able to shoot groups equal to or smaller MOA-wise than that, then spend the rest of my energy mastering wind reading, shooting techniques, etc... Whether I'm shooting steel, milk jugs, X-rings, deer vitals, or the broad-sides of barns lol

Great post, and that makes perfect sense. I like your idea as far as building a rifle to the specifications needed. You could also try to tailor loads to fit this criteria.

#### 16Bore

##### Well-Known Member
Now apply a time and cost model to chase a rifle from 1 MOA to .1 MOA and one might really see what diminishing returns are all about.

#### pyroducksx3

##### Well-Known Member
But when will this WEZ program be available on a mobile device to the civilian market? Or has that been made available now?

#### CB11WYO

##### Well-Known Member

Agreed.

If faced to make a choice between aTerrapin and uncertainty analysis I’d dump the Terrapin in a heartbeat. IT’S THAT IMPORTANT! Why? Two fold. First, as mentioned in the article, WEZ allows one to examine percentage difference with a change in input. When does one stop chasing precision in favor of accuracy? Where are time and resources best utilized for maximum return? WEZ provides comparison in terms of hit percentage return. Second and most important falls in line with the nature of this forum. WEZ allows one to annotate most likely hunting condition cold bore first round hit percentages onto range cards. A hunter can use this information to hunt percentages in lieu of fixating on a set range. For example, if a hunter has determined they will not risk taking a shot with less than 90% assurance of striking vitals, WEZ is capable of this analysis. An egg-headed person who is into “this stuff” will have already figured out how to do this by the time they complete reading the post. For the rest, it would be great if an article could be linked on how to do this...hint…hint. Fixating on shooting percentages rather than range is a tremendous advantage with this type of program and worth every penny. BTW, I’m glad I don’t have to make the decision to dump my range finder. Let’s hope that day never comes!

Uh oh... I think I'm an egg-head

I agree BTW