Group size: Moving towards using 10 shot ATC instead of ES

[ColtJ]

Good points.

I tend to use an app on my cell phone but it measures based on the two farthest points. 'Target Calculator' on Android.

As far as the number of rounds, for discussions sake maybe we should set regulations such as minimum shots per group atleast within the forum, etc... IE: 3 round sub MOA and 10 round sub MOA groups are two different things and not comparable even though both are "sub MOA".

For reference heres a group using the software mentioned above:

[mizer67]

Good points.

I tend to use an app on my cell phone but it measures based on the two farthest points. 'Target Calculator' on Android.

As far as the number of rounds, for discussions sake maybe we should set regulations such as minimum shots per group atleast within the forum, etc... IE: 3 round sub MOA and 10 round sub MOA groups are two different things and not comparable even though both are "sub MOA".

For reference heres a group using the software mentioned above:

There appears to be something wrong with that program or the data input into the program. MOA is calculated improperly, or so it appears.

[ColtJ]

There appears to be something wrong with that program or the data input into the program. MOA is calculated improperly, or so it appears.

May I ask why you think it calculates improperly?

Thanks.

[mizer67]

May I ask why you think it calculates improperly?

Thanks.

1 MOA = 1.047 inch @ 100 yards.

Your picture from the application you'd posted shows them as equal to each other, for example, 1.050 inches = 1.050 MOA. That is a minor flaw in the program or data, or so it appeared to me.

[Travis B]

1 MOA = 1.047 inch @ 100 yards.

Your picture from the application you'd posted shows them as equal to each other, for example, 1.050 inches = 1.050 MOA. That is a minor flaw in the program or data, or so it appeared to me.

Yeah, I noticed that flaw as well. But who's splitting hairs?

[ColtJ]

I see. Missed that completely.

Its still a convenient tool and guess i can do the math myself to get the exact result.

[ROGOPGEAR]

There appears to be something wrong with that program or the data input into the program. MOA is calculated improperly, or so it appears.

technically yes. practically, it doesn't matter. most consider 1inch to be MOA at 100yds and just drop the .047 for ease of calculations. At 1000yds that difference doesn't even equate to 1/2 inch yet. but, for a technical program, you could consider that an oversight.

[mizer67]

technically yes. practically, it doesn't matter. most consider 1inch to be MOA at 100yds and just drop the .047 for ease of calculations. At 1000yds that difference doesn't even equate to 1/2 inch yet. but, for a technical program, you could consider that an oversight.

Yes, I know.

I just can't stand a lack of attention to detail in my line of work. It's a compulsion.

[P2000]

For a phone app, that is pretty neat. At least a 10 shot group is used, and you could correct it to actual MOA if you wanted to.

However, I will still beat the "ATC is better" drum.

Remember that with extreme spread, you are only measuring the difference between your two furthest apart shots.

If you shoot several 10 shot groups and calculate both extreme spread and ATC on each group, you will most likely observe that the extreme spread tends to vary more from group to group. ATC tends to be more consistent.

Using ATC, every shot is measured by how off center it is. But with ES, a shot being off center may or may not matter, depending on where the other worst shot has landed....it makes little sense. As a shooter, we are trying to hit a target, not make our misses closer to our other misses.

For an extreme example, imagine one group shaped like a doughnut, where no shot hits the center, but all shots miss around the perimeter. Then imagine another group where you have 8 dead center hits, but two shots that are off. Both of those groups could have the same ES measurement, but using ATC the group with 8 hits would measure significantly better. It should measure better because you hit dead center 8 friggin' times!

[P2000]

Here is a quick and sloppy illustration of my last point. Please note that this is just an extreme example to highlight the differences between ATC and ES.

Using ES, these groups measure about the same. Using ATC, these groups are very different. Clearly, the first group is much better, and ATC shows it.

Group 1. ATC= 0.251 MOA
ES= 1.474 MOA




Group 2. ATC=0.700MOA
ES=1.519