I hear this so much, what the heck do they mean when they say it? I understand minute of action & all this, degrees within a radius, the distance thing, a ton of math.... but what do people mean when they claim that there rifle shoots MOA? Shoots well enough to measure with the science of MOA? I understand what a guy is talking about when he says he shoots a .850 3 round group at 100 yds..... but when someone says they shoot MOA.... I dunno, help me out here.
wearing my ignorance on my sleeve here.

Minute of Angle - slightly over 1" @ 100yds.

And thats very slightly over 1 inch. Most just use the term 1in = 1moa at 100 yards.

1 minute of angle is 1.047" @ 100yds.

The way MOA comes into play is that when I say I shot a 1/2" group, well that could be @ 100, 200, 300 yds. Entirely different levels of accuracy. If I say I shot a 1/2 MOA group, well, the distance becomes somewhat less important as generally speaking, 1/2 minute @ 100yds (1/2") is angularly the same as 1/2 minute @ 300yds (1-1/2"). This also comes in handy when you start shooting longer ranges, or multiple yardages in one match... instead of trying to remember that the clicks on my scope or sight move the center of my group 1/4" at 100yds, and then mentally translating that into however many inches at the distance I'm shooting at, and then figuring how many inches I need to move, and thus how many clicks, a 1/4 minute click moves the group 1/4 minute at any range you shoot at... whether it be at 100yds, or 600yds. If you are shooting a sport that has the targets laid out in roughly minute intervals (example: NRA Highpower targets have 1 minute X ring, 2 minute 10-ring) you can look at where your bullet impacts and if it's on the edge of the 10-ring, one minute of correction should put you in the center of the X ring. A lot faster and easier once you get used to it than figuring in inches.

HTH,

Monte

very good, thank you. That clears it up for me.