Interesting Find, Bullet Base to Ogive...

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jetinteriorguy

New member
Whenever I shoot more than ten rounds and they are say 1/2-3/4 MOA, I’ve noticed the more I shoot at that target the bigger the group becomes. I think it’s because focusing on the hole in the target causes me to allow a little more movement without realizing I’m not completely settled in. I’ve done one thing that at least in my case kind of supports my notion, I’ll shoot multiple groups of ten and then overlay the targets and find the aggregate of these groups tends to stay in a smaller size group.
 
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Unclenick

Staff
Actually, that happens even with a machine rest. The more rounds you shoot, the more chances you are giving outliers to appear. This plot shows expected size of a group with the same radial standard deviation as the shot count increases:

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milboltnut

Moderator
I know Sierra has pretty tight tolerances with bullet runout.
from thier website...

Jacket concentricity of .0000″ to .0003″ on target bullets and .0000″ to .0006″ on hunting bullets.
Click to expand...
 
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kilotanker22

New member
jetinteriorguy said:
Whenever I shoot more than ten rounds and they are say 1/2-3/4 MOA, I’ve noticed the more I shoot at that target the bigger the group becomes. I think it’s because focusing on the hole in the target causes me to allow a little more movement without realizing I’m not completely settled in. I’ve done one thing that at least in my case kind of supports my notion, I’ll shoot multiple groups of ten and then overlay the targets and find the aggregate of these groups tends to stay in a smaller size group.
Click to expand...
I always adjust my sights slightly so I do not impact my aiming point when shooting groups at 100 yards.
 
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Unclenick

Staff
hounddawg said:
Statistically that is true Nick but math seldom tells the whole story. For some shooters getting a 9 after 19 X's and 10's is the outlier, for others like myself getting a 8 after 19 X's, 10's and 9's is the outlier
Click to expand...

Oh, the math won't stop outliers or even account for them in any specific way other than to say how often to expect them and to not give them too much weight. That's not the point. The point is to get the most representative possible idea of the gun and shooter's combined precision in the fewest total shots using up the least barrel life possible. So while you can do it with ten round groups, because group diameter is dependent on just two shots out of the total number in the group, you wind up firing a larger total number of uncounted rounds (the ones that aren't either of the two that define your group size) to get the same certainly in your information about how precise you and your gun are.

So that paper I linked to is just a statistical method of cutting down how many rounds you need downrange to check performance or to learn what a change in your technique (either loading or shooting) has done to your overall precision. Knowing where every single shot lands remains the method that uses the fewest total shots of all. I've been looking at the less expensive sonic shot locators for this reason, though the accuracy limit on them (as compared to the more expensive ones) is a little discouraging. Meanwhile, I just don't shoot so many on each bull that I can't find all the individual holes in On Target TDS.
 
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jetinteriorguy

New member
Well I’ll be darned, good idea. Thanks, I definitely never would have thought of that. Just goes to show, ya learn something new every day as long as you pay attention. Oops, forgot to link to post#45.
 
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Unclenick

Staff
That looks like a good way to make it printable. The standard benchrest bull is another to consider. The ink pad and stamp to put them on paper are still available. That way you can stamp it on tagboard stock if your printer finds tagboard too heavy to handle, and still enjoy the cleaner holes you get in tagboard as compared to typing paper.
 
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