Hit percentage analysis

[Bryan Litz Ballistics]

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:
http://precisionrifleblog.com/tag/applied-ballistics/

-Bryan

 

[spclark]

Yep, good read. "Diminishing returns" pretty much rules all human endeavors, right? At some point it's just not worth the time, $$ or effort to keep 'squaring the circle' so to speak.

Not checking my front sight's tightness last weekend at 900 yards cost me maybe half the points I dropped (9 in all) out of 450. Some things matter more than others, that's clear.

 

[eric32]

pretty good read, looking forward to the rest of the series.

 

[DataSmith]

OK, if I have my head in the dark place, forgive me...

I read an article Bryan wrote on WEZ and it took a bit of time for me to wrap my head around the ideas. But then I began to see that he was saying the same thing I've been thinking for quite some time.

This is a fairly common issue, where the increase in effort does not produce a linear increase in goal attainment. In a case like this, the small things that are working against you start to have a more disproportionate effect as you eliminate the larger impediments.

There is a lot of emphasis on equipment and ammo in the precision community. But I have to wonder when is enough, good enough? At what point does the minute attention detail stop having a measurable practical advantage for a given shooter?

My experience in pistol competition shows me that a good shooter with a stock gun and ammo can usually out shoot a not-so-good shooter with the best money can by. IOW, the monkey behind the gun is often the critical factor.

I'm still something of a hack and probably always will be because I simply don't have the time or access to the facilities to practice the way I would like to. My goal is not to out shoot anyone other than myself. As long as I do better than I did the last time, then I'm making progress.

As a result, until I'm in the position of being able to get to a range on a regular basis and practice, I'm hesitant to spend more time and money on refining my rifle and ammo than I already have.

----------------------
For background, I've spent most of my life working in the sciences in one way or another. For most of 20yrs I worked in medical labs and taught various subjects. One of the topics that was always difficult to deal with was quality control. This was largely because even people working in the field have a certain resistance to understanding statistics and variability. In a field where precision is everything, it's hard to accept the fact that there can be so many variables involved that's it's not possible to reach 100% 24/7.

This is where the issue of diminishing returns comes in. Given that there is only so much you can do, it makes sense to concentrate on those things that have the greatest chance of improving the precision. This is where having good equipment and quality supplies is important. But the greatest source of error is not the equipment and supplies - it's the operator. Human error accounts for more bad results than anything else. I could see that fact play out time after time after time as a teacher and lab supervisor.

 

[Jay Christopherson]

That was pretty interesting and very good writeup.

 

[XTR]

I've been telling new shooters for yrs not to get wrapped up in internet reloading. It is not that hard to make bullets that shoot ½MOA or so, and with a little load work you can get to into .3s vertical at 300 yds*. (*when I say that I mean shooting in no wind at 300 yards)

For long range F-class I've argued for yrs that the surface area of 10 ring that you gain (or 9 ring you lose) by dropping your load from a ½ MOA load to a ¼ MOA load is really quite small, and the over all difference you probably wont notice in your scores, because an 8 has nothing to do with our load and everything to do with wind reading.

If the average newbie F-TR shooter would get a FL sizer, a Lee Collet die, and load somewhere between 43.5 and 44 grains of Varget, depending on throat, behind a 185 Jugg and go shoot they would be better off than chasing their tail with neck turning, weighing brass and bullets and futzing with QL. None of that stuff will teach you to see a letoff.

Now, if you are chasing the top of the leader board on the national level, and you need Xs, then sure, it may help, and it will at least make you feel better, but if you are consistently shooting in the low to mid 180s none of that is going to help you.

 

[CB11WYO]

Good perspective and awesome insight with meaningful applications, especially for new shooters.

 

[DataSmith]

One thing I keep thinking about is a class I was in a couple years ago. We were shooting as shooter/spotter teams. The guy I was shooting with had a pretty expensive rifle and ammo, while I had a tactical Rem 700 with nothing-fancy handloads.

Now, this guy was dead-nuts precise, he could put one bullet on top of another at 100yds. But he couldn't estimate distance or read wind to save his life - it's not something he had trained to do. So I was out shooting him at every distance past about 300yd and more often than not had to talk him onto the target.

 

[CB11WYO]

...But he couldn't estimate distance or read wind to save his life - it's not something he had trained to do....

And that'll make all the difference! As you pointed out...

 

[barefooter56]

DataSmith,
Your "dark place" is actually a ray of light!!! This post should be read by hunters and target shooters alike and taken to heart. Unfortunately the EGO often overrules the obvious. The lack of skill of the "loose nut behind the butt-plate"is a major part of the equation. You can do only so much with the ammunition. You have to practice! And not always on calm days to get where you want to be.

 

[jlow]

I certain agree that shooter skill is a huge part of the game, but the thing to keep in mind is if you ONLY look at hit percentage as a function of MOA accuracy of the round, this simulation assumes that the shooter is always aiming and hitting dead center on those targets. Once you go past that and take a look at hits which are no longer center because of things like slightly improper range dope, vertical stringing because of MV variation, the accuracy of the rounds will make significantly more of a difference. This is because it will essentially significantly reduce the size of the 10” plate which at 1 MOA dead center aim encompass most of the spread of an 1 MOA accurately aimed round but when the aim is off, this no longer happens.

I really would like the author to continue the simulation and tell us how much hit percentage is affected if the aim was off by different degree i.e. this is really only half the story.

 

[Bryan Litz Ballistics]

jlow,

You make a good point. The AB Analytics tool currently doesn't support modeling of 'off-center' groups; something we all know is very common.

The analysis tool is giving you best case scenario for hit percentages amidst uncertainties in: range, wind, MV, and inherent precision (MOA group size) for different size targets as a function of distance. Incorporating an 'off center' group parameter would be a good thing, but how would you know how much to model your group to be off center?

This topic is addressed in detail in the book: Accuracy and Precision for Long Range Shooting" (which you can get a $5 coupon code for in this thread: http://forum.accurateshooter.com/index.php?topic=3862174.0 )
This book looks at the uncertainties that will spread a group out (precision) as well as those which would put a group off center (accuracy). Elements which are discussed in detail regarding accuracy are:
How much does scope cant affect accuracy (group centering)
Trajectory modeling errors
Accounting for secondary effects such as Coriolis and spin drift
Calibrating ballistic solutions to mitigate such errors.

I think someday the AB Analytics tool will have the ability to model off-center groups. Currently I'm wrestling with the question: should the group center offset simply be a user input, or should it be tied to some physical effect like scope cant, spin drift, inaccurate BC, etc?

-Bryan

 

[jlow]

Thanks Bryan! The reason I ask is specifically from reading your book in question (which BTW I have and is currently enjoying!) For example, on page 122, you appear to be able to do analysis for both centered Group and spin drift error group, thus the question. Having said so, I don’t know the software involved and potential challenges from what I requested.

Basically my comment was to make sure that the reader of this thread understand that this is the “good news” but all too common, we cannot achieve those conditions and so the “bad news” is also a reality.

 

[jlow]

I was interested in seeing how a slight “off-center” aim might affect hit rate using the same data and I made this crude simulation. What I basically did was to download the graphics from the PRS blog, draw another 10” and 20” target using Photoshop, made them red, and placed them over the same shot patter but offset by ¼ diameter of the plate i.e. the aim was slightly high.

You can see for the two targets, the slight mis-aim where the center of the shot group was 2.5” higher (10” target) or 5” higher (20” target), really only caused a slight loss in hits (represented by those hits above the red circle) for “prefect ranging”. Whereas for the 5, 10 15 yards mis-range, you are losing a lot more fired rounds which completely miss the target and it quickly gets worse the less accurate you range.

Not nice and quantitative like Bryan’s computer simulation but you can see the gross effects.

 

[CharlieNC]

If not careful, the reader may be misled by the conclusions from this test case which deals with a 20" target at 1000yd. Thats a large target, and I expect the conclusions would differ quite a bit for smaller targets such as Fclass Xring.

 

[jlow]

I think the test is aim at PRS shooter so not so unreasonable target size from that standpoint, but yes, it will be quite a completely different thing for F-class....

 

[jj789]

how does all of this apply to bench rest shooting where both group and score count ???

when the small group counts is the extra time and effort worth it ??

 

[barefooter56]

jj789,
Reading conditions, rifle tracking in the bags, set up of bags and rest on bench, rifle handling ( head position, trigger control ETC).
In short PRACTICE with the rifle in all conditions so you know it. A hard shooter with a 1 MOA load will beat a mediocre shooter with a 1/2 MOA load (or less) every time. Same thing applies to ALL shooting disciplines. YOU HAVE TO PUT IN THE ROUNDS IN ALL TYPES OF CONDITIONS. Precision reloading is a smaller part of the equation than shooter skill IMHO. But having said that . I know that there are shooters that shoot to reload and shooters that reload to shoot. To each his own.

 

[Joe Salt]

I agree with shooting ability, at the beginning of the year my buddy Ed and I always say to each other after a long winter off.( We have to learn how to shoot all over again) That means set up an all. If we done it every day we might have a better chance.

Joe Salt

 

[Dos XX]

If the average newbie F-TR shooter would get a FL sizer, a Lee Collet die, and load somewhere between 43.5 and 44 grains of Varget, depending on throat, behind a 185 Jugg and go shoot they would be better off than chasing their tail with neck turning, weighing brass and bullets and futzing with QL. None of that stuff will teach you to see a letoff.

Wade, are you telling me a 10% BC gain won't fix my 7? Now what?