Not that he needs my help, but you guys who are arguing with Formid need to understand that his explanation isn't even really about shooting, it's about statistics and probability.

Originally Posted by Bluedreaux

Originally Posted by Formidilosus

Using you 2.5 MOA gun example, since any 4 rounds can be anywhere within that 2.5moa circle, when the 4 rounds impact closer to the edge rather than the middle, how do you determine that it wasn't because of a zero shift instead of random distribution?


I don't. And I don't care.

Because the zero shift, or shooter error, or inaccurate ammo, or bullet weight that doesn't fit the twist, or random distribution, or any number of potential causes for the dispersion is always within that 2.5MOA circle and has been for the last 8 years or so that I've owned that rifle.


Actually, if that's your explanation then you might realize that you aren't basing your zero off a 3- or 4-shot group, but rather a group that probably numbers in the hundreds, fired over time at dozens of targets, cold barrel, warm barrel, etc. As much as the thought may appall you, you are basically agreeing with Formid.

If you fire a 10-shot group, the first 3 might be one near POA, one towards 3 o'clock and one towards 6 o'clock. Would you question your well established zero if this happened? The next three might be a little high and to the left. This isn't because the barrel is getting warm, it's simply probability at work, with everything eventually balancing back to the mean. Heck flip a coin 4 times and get 3 heads and 1 tails, what do you make of that?

The point is, 3-4 shots is not enough data points to judge your true zero... there is 360 degrees and infinite distances of dispersion to account for, and by your own admission you are acknowledging that.

As far as cold bore shot #1 vs. 2-10, I don't think Formid is saying they need to go into the same hole. Rather, they need to go int the same GROUP. Fire 5 10-shot groups on the same target and let your barrel cool down between each GROUP. If you end up with two different groups, with the #1's going into one group, and #2-10's going into another distinct group, then yes, you have a broken gun.