Here is a 20 shot group

[alb]

AAlex,

Interesting comments. When I first got my pistol, I changed my sights a lot. But that was because it wasn't correctly sighted in when I bought it.

Now, as a practical matter, the only time I change my sights is when I change from shooting one-handed to two-handed, or when I change the distance at which I'm shooting (wind isn't a factor where I shoot).

I find that when I'm shooting well (for me), my shots almost always seem to go where I think they went. Lately, I've been having an occasional problem with flinching. When I throw a shot low-right, I pretty much know where to look for the hole. When I throw a shot to the left, it's almost always a surprise.

When I get tired, or my NPA is off, I have to exert more effort to put the shot where I want, and my groups open up. But, when I practice, I shoot 50 or more shots at the same target, and the center of my groups hardly varies at all, from target-to-target, from day-to-day, or from week-to-week.

My point is, I know from experience that whatever temporary flaw in my technique caused me to throw a couple of shots in a row in a certain direction, it is temporary, and will even itself out over the course of a match, or a 50-shot practice string.

If I adjusted my sights every time I threw a few shots to the left, then a few shots later, I'd have to undo the adjustment when I started shooting to the right. If I were to shoot what would have been a 10 at that point, it would end up as a 7 to the right. And if I shot what would have been a 7 to the right, it would turn in to a 3 to the right. My scores would suffer considerably.

There is no point in chasing transitory, random variations in shot placement -- and yes, they are random unless you can tell for certain what caused them. This strategy only reduces the effective accuracy of your pistol. And my experience tells me that longer term shifts in POI just simply don't happen.

Shot placement does indeed follow a 2D normal distribution. And triggering errors don't cause fat tails -- they occur randomly also and they just make the variance larger. They do, however, result in a fat-tailed distribution of the size of your groups. So, for accuracy testing, simply shoot a relatively large number of shots and drop some percentage of the outliers. This dramatically reduces the variation in the size of your groups. In fact, the military drops the worst 50% of the shots, which results in a very stable measurement of group size/accuracy with a relatively small number of shots. As a practical matter, this isn't feasible at short range with something like an air pistol, because it isn't possible to distinguish the worst 50% of the shots.

There are far too many variables that go into balancing on two feet, holding a pistol at arm's length, controling your breath, minimizing your wobble, etc. for anyone to be concious of all of them at the same time. So, while in some philosophical sense, nothing about shooting is truly random, as a practical matter, it makes a lot more sense to approach it with a probabilistic perspective.

Regards,

Al B.

[tleddy]

I have been following this thread for some time; it is a great deal of fun to see the various analytical dissertations and I REALLY enjoy them.

I am a simple country med tech with a minimal grounding in stats, so this gives me an education (when I can follow the math).

Thanks!!!

Tillman

[Chris]

How is the person who posted the 20 shot group shooting now?

[jackh]

All math and science aside, only experience will tell you to move the sights after one shot or many.

[Axel]

All math and science aside, only experience will tell you to move the sights after one shot or many.

Indeed.

[2650 Plus]

Rules for changing sight settings. I am a shooter not an engeneer,. As the joke goes I can't even spell it. First shot on my target is a nine at three oclock. I called a center ten. Depending on how confident I am of the call I may move one click right. Second shot is a ten but off call to the left . I take one click right. Third shot is a scratch ten right and on call . No sight change. Fourth shot is a nine high, call was good but questionable . No change to sights . Fifth shot is high nine, call was good. I now have two consecutive shoots high. I consider a sight change. Rational A nine high counts exactly the same as a nine low . But I decide not to change the sight . Sixth shot is high nine DAMN. No more messing around I cone down One click. Remaining shots on call and centered group. What do you see wrong with the idea that adjustable sights are placed on the pistol for a reason. Good Shooting Bill Horton

[alb]

What do you see wrong with the idea that adjustable sights are placed on the pistol for a reason.

What's wrong with it is that every time you move the sight 1 click, you're adding 1/2 MOA to the diameter of your group. If you are doing this to compensate for variable wind conditions, then you could reasonably argue that it is really the wind that is adding that 1/2 MOA.

On the other hand, if what you are doing is attempting to compensate for “lack of perfection,” then all that you will accomplish is to lower your score.

Let’s take a practical example. One of the pistols used for 2700-Bullseye competition is the M1911 .45. Les Baer sells a high quality wadcutter .45 for this type of competition that is guaranteed to shoot 10-shot 2.5 inch groups at 50 yards, using match-grade factory ammunition and shot from a Ransom rest. Now, using that math that people hate, and the formula developed by H.E. Daniels in 1952, we can calculate that the average size of a 60-shot group is about 1.4 times the size of a 10-shot group (all due to “lack of perfection,” i.e., “dispersion”). So, that 2.5 inch 10-shot group translates into a 3.5 inch, 60-shot group at 50 yards, i.e. a 7 MOA diameter group.

By the way, I picked the .45 for this example because it has a particularly high “lack of perfection.”

Now, let’s apply your strategy for adjusting the sights, still using the perfect shooter – Mr. Ransom rest, on a totally windless day. 1 click left, eventually 2 clicks right, and eventually 1 click left again – back where we started. Again, 1 click up, eventually 2 clicks down, and eventually 1 click up again – again, back where we started.

What have we accomplished? Well, what we’ve done is to turn what would have been a 3.5 inch, 7 MOA group into a 4 inch, 8 MOA group. If we had been keeping score, applying your strategy would have cost us points – not a good thing.

Now, let’s turn to 10 meter air pistol. A high quality air pistol is capable of putting all 60 shots through the same hole at 10 meters. Unfortunately, you’re not, and neither is anyone else. That’s because we humans, like everything else, suffer from a “lack of perfection” – and some of us are less perfect than others. If we apply the same strategy of adjusting the sights to compensate every time we shoot a less-than-perfect shot, all we will accomplish is to lower our score, just like in the example above.

The thing is, that lack of perfection is random – sometimes we shoot a little high, sometimes a little low, sometimes a little to the right, sometimes a little to the left. It’s called “dispersion,” and every shooting system has it. And you can’t compensate for randomness. But you can account for it, and you can measure what is left after you’ve eliminated that randomness.

Then, and only then, should you make adjustments to your sights.

Regards,

Al B.

[2650 Plus]

The 45 is amazingly accurate and my experence with one is that they shoot better in my hand than they test in a machine rest. But that is all immaterial. If the shot is off call and you have confidence in the call and in the accuracy of your pistol then , I submit that every shot is a zeroing shot. Maybe even an accidental center hit if you didn't call it there. However, I dont care if my competition never moves his/her sights. Adjusting sights is always a personal decision and only the shooter can make an assessment of the correct action to take. Good Shooting and don't be welded to your sight setting, Stuff Happens. Bill Horton

[shadow]

When is the Germany trip?