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Help - developing a bad shooting habit?

You know - you guys really got me thinking here, which is great! If I look back at some of these 100 yard "0.5MOA targets" where I was shooting multiple groups of 5 shots. any individual group has an ES of .4-.6 basically so they average out to 0.5... if you were to take all the individual groups and over-lay them, so in this example 40 shots, so that the point of aim was identical on them all, there is no way they'd have an ES of 0.5 MOA. in fact, it just eyeballing it, it looks like it would be approximately (wait for it) 1MOA. Just like these larger groups of 15 I've been shooting at 200 and 300 yards!

Now its really easy to rationalize this away: Oh, because I was shooting 5 and then breaking cheek weld, etc my point of aim got tweaked slightly, yadda yadda but the reality is that I need to put 15 shots on target for the game I'm playing, not 3 groups of 5 or even 8 groups of 5

According to Litz, using 5x5 groups with ES should get you the same result at a single group of 15 using mean radius but I'm starting to wonder if thats actually true...
 

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500 rounds on a 6 Creed barrel means your throat have moved a bunch. Check your loads and seating depth. Probably carbon too.

Shoot them again at 100y. I would also try shooting less time at different targets, black dots, green dots, something with a prominent aiming point. Try a few different types. Maybe try again but from prone. Listen to the Boss, he had good input. Also put down the books about shooting and go practice at the range :)

Heh - Im putting ~200 rounds down range a week, so its not as if sitting around just speculating. I can't practice much more than that without getting a smacking from the wife or have time to both reload 'em and shoot 'em.

However reading books while sitting on the can... she'll never know about that time wasted ;)
 
The wind will make a shot go out 2 moa if you get the right switch no matter what your program tells you. If youre not using flags youre doing better than expected. Between mirage and switching summer winds you can get blown off that target at 200
 
500 rounds on a 6 Creed barrel means your throat has moved a bunch. Check your loads and seating depth. Probably carbon too.

Shoot them again at 100y. I would also try shooting less time at different targets, black dots, green dots, something with a prominent aiming point. Try a few different types. Maybe try again but from prone. Listen to the Boss, he had good input. Also put down the books about shooting and go practice at the range :)



Good points.
 
You know - you guys really got me thinking here, which is great! If I look back at some of these 100 yard "0.5MOA targets" where I was shooting multiple groups of 5 shots. any individual group has an ES of .4-.6 basically so they average out to 0.5... if you were to take all the individual groups and over-lay them, so in this example 40 shots, so that the point of aim was identical on them all, there is no way they'd have an ES of 0.5 MOA. in fact, it just eyeballing it, it looks like it would be approximately (wait for it) 1MOA. Just like these larger groups of 15 I've been shooting at 200 and 300 yards!

Now its really easy to rationalize this away: Oh, because I was shooting 5 and then breaking cheek weld, etc my point of aim got tweaked slightly, yadda yadda but the reality is that I need to put 15 shots on target for the game I'm playing, not 3 groups of 5 or even 8 groups of 5

According to Litz, using 5x5 groups with ES should get you the same result at a single group of 15 using mean radius but I'm starting to wonder if thats actually true...

I'm going to respond to myself here because I just realized I was having a large mental error in considering these groups and they're actually not nearly as different as I have been thinking. Long story short - the average ES of 5x5shot group is -not- equiv a 15 shot group and the effect of moving from 100->200->300 yards is larger than I had been thinking too. So while I've been thinking my shooting has gone from 0.5 MOA average (for 5 shot groups) to hell in handbasket and now I'm suddenly shooting 1.0-1.2MOA, the numbers simply aren't equivalent because I haven't been applying appropriate scaling.

Using some formula's from Litz's book and data I was able to excel up a little chart:

Screenshot from 2018-07-05 21-30-36.png


Plugging this in for a 100 yard 5 shot group average of .5 MOA (what i've shot a lot of previously), I should -expect- to see .86-1.05 MOA on the target at 200-300 yards (what i have been doing lately).

So now taking a look at those 200 and 300 yard targets I wasn't happy about... Low and behold I'm seeing 1-1.2 MOA depending what particular group you look at. Do the reverse calculation and that means the 5-shot 100 yard groups would look like 0.60 MOA. The difference between a .5 and .6 MOA for any given 15 shot group can clearly be the difference of just one shot and probably isn't statistically significant.
 
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1. About wind -- As I wrote before, 90 degree X-wind at 200 yards has roughly FOUR Times the effect as 200. Rule of the Square. So if you have 1" of push at 100 you will have roughly 4" at 200. Obviously if the wind is variable or shifty you will see a very large increase in horizontal dispersion.

If you don't believe, here are JBM Ballistics numbers for a 6.5 caliber, Berger 130gr VLD, 2900 FPS MV, 10 mph 90-deg crosswind

Drift at 100 yards: 0.5"
Drift at 200 yards: 2.2"

Ratio in inches = 4.4

Five vs. Fifteen
My goodness 5 rounds at 100 vs. 15 rounds at 200? Absolutely no way you could expect to replicate the MOA of 5 with 15. Not even in a tunnel

Jim See, a top PRS guy, likes to have a rifle that will "hold half-MOA for five (5) shots, 3/4-MOA for 15 shots, and 1 MOA for twenty shots".
 
1. About wind -- As I wrote before, 90 degree X-wind at 200 yards has roughly FOUR Times the effect as 200. Rule of the Square. So if you have 1" of push at 100 you will have roughly 4" at 200. Obviously if the wind is variable or shifty you will see a very large increase in horizontal dispersion.

If you don't believe, here are JBM Ballistics numbers for a 6.5 caliber, Berger 130gr VLD, 2900 FPS MV, 10 mph 90-deg crosswind

Drift at 100 yards: 0.5"
Drift at 200 yards: 2.2"

Ratio in inches = 4.4

Five vs. Fifteen
My goodness 5 rounds at 100 vs. 15 rounds at 200? Absolutely no way you could expect to replicate the MOA of 5 with 15. Not even in a tunnel

Jim See, a top PRS guy, likes to have a rifle that will "hold half-MOA for five (5) shots, 3/4-MOA for 15 shots, and 1 MOA for twenty shots".

My wind thinking is slightly difference since its all about the relative amount in my groups I could "blame" the wind for with crappy calls, but your math matches mine in absolute terms. If its 10mph constant, then its trivial to adjust for, but on a mostly windless day (when I try and shoot groups), if I can't call the wind call right within 5mph by simply waiting out any breeze, then I should go home. So a 90 degree cross wind for my 147 ELD @ 2708 is .22MOA horizontal at 100 yards within a 5mph window. at 200 yards is .45 MOA, and .69 MOA at 300 yards. thats also worst case, if its down/up range its more forgiving. I don't think I can blame my crap groups on the wind unfortunately... though I probably need to stop thinking about 300 yard groups for testing unless its truely a windless day!

Agree on the Jim See quote: thats why I was saying above that even with what I thought was my "problem" its all clearly good enough for what I'm doing. 1 MOA for 15 shots its a precision scalpel compared to my 4 MOA of wobble in a shittily built position. .5 MOA for a 5 shot group at 100 is 1.65MOA for a 1000 yard 20 shot group. Its all windage at that point for a 1-2 MOA piece of steel that far out
 
Just thought I'd post back here in case anyone stumbles on this thread later. I decided to go out and test @ 100 and @ 300 same day. .443 MOA 5-shot group at 100 to check zero - no problem. 2, 15 shot .96 MOA goups at 300. I didn't think to take a pic of it but then went back to 100 and shot another couple .5-ish MOA groups.

According to my fixed spreadsheet above - .5 5-shot at 100 is going to translate to .95 15-shot at 300. looks like I'm pretty much within expectations. Still going to go practice more dry firing however as suggested above and I did keep track of reticle jump. I consistently end up with x-hairs ~4 MOA left of target so the gun isn't tracking straight back. I'll have to figure out what I can do to help it track better.

TgtGfx.jpg
 
I'm going to respond to myself here because I just realized I was having a large mental error in considering these groups and they're actually not nearly as different as I have been thinking. Long story short - the average ES of 5x5shot group is -not- equiv a 15 shot group and the effect of moving from 100->200->300 yards is larger than I had been thinking too. So while I've been thinking my shooting has gone from 0.5 MOA average (for 5 shot groups) to hell in handbasket and now I'm suddenly shooting 1.0-1.2MOA, the numbers simply aren't equivalent because I haven't been applying appropriate scaling.

Using some formula's from Litz's book and data I was able to excel up a little chart:

View attachment 1055975


Plugging this in for a 100 yard 5 shot group average of .5 MOA (what i've shot a lot of previously), I should -expect- to see .86-1.05 MOA on the target at 200-300 yards (what i have been doing lately).

So now taking a look at those 200 and 300 yard targets I wasn't happy about... Low and behold I'm seeing 1-1.2 MOA depending what particular group you look at. Do the reverse calculation and that means the 5-shot 100 yard groups would look like 0.60 MOA. The difference between a .5 and .6 MOA for any given 15 shot group can clearly be the difference of just one shot and probably isn't statistically significant.

What you are seeing is a basic statistical property of the normal distribution that applies to EVERYTHING, and shooting data is just one example. The ES (group size) will continue to grow as the number of samples increases, BUT the standard deviation begins to level off substantially at around 20-30 sample size. That is one aspect why it is better to use SD instead of ES for virtually everything we measure, and in addition it is a direct application to determine the % chances that various outcomes ( group size, score, etc) will happen. Velocity is another good example to use SD. This is not to say that everything follows a normal distribution, including target data for extremely small group sizes.
 
What you are seeing is a basic statistical property of the normal distribution that applies to EVERYTHING, and shooting data is just one example. The ES (group size) will continue to grow as the number of samples increases, BUT the standard deviation begins to level off substantially at around 20-30 sample size. That is one aspect why it is better to use SD instead of ES for virtually everything we measure, and in addition it is a direct application to determine the % chances that various outcomes ( group size, score, etc) will happen. Velocity is another good example to use SD. This is not to say that everything follows a normal distribution, including target data for extremely small group sizes.

Right - and this is the problem with damn statistics. Your (or in this case my) quick calculations can be substantially different then when you actually do the math =p
 

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