[Rusty A]

In measuring a shot group, do you draw a circle around the whole group, then measure the diameter or the radius of the circle? Which measurement do you use?

[mx308250]

Measure the two farthest shots then subtract thediameter of the bullet. For example my last 3 shot group was .628 from my .308 which is 30 caliber. So the spread for 3 shots was actually .328

[Rusty A]

So, if I had three shots in the same hole, I would have a shot group smaller than the bullet?

[billy]

USE CALIPERS
measure the diameter of the bullet HOLE from smudge to smudge.
then measure the group at it's widest point from smudge to smudge.
subtract the bullet hole size.

the smudge is the grey stuff on the edges of the bullet hole.

[billy]

thats how the benchrest guys do it.

[cremley]

Well, that changes a lot of my group sizes!

[mosin warrior]

Yeah that is how the benchrest guys do it, but I typically think of group size as the diameter of the circle that the group would fit into.

[billy]

it all depends on if you want an accurate measurement or not.
we get it down to the 0.000

for online matches we have to do it this way because so many guys get so close to each others scores.

[billy]

Quote:       Originally Posted by mosin warrior

Yeah that is how the benchrest guys do it, but I typically think of group size as the diameter of the circle that the group would fit into.

some fabulous groups got disqualified here last week because they didnt measure according to the rules.

one guy would have won for sure!
if you want to be taken seriously .
measure like the big boys.

[Darkfront]

Groups are measured center to center of the two furthest shots. That's what the whole smudge to smudge minus bullet diameter does.

[big shrek]

I don't have a pic to show the process, but one would probably assist many new shooters into understanding how it works...HEY BILLY!!!

I trust Billy to have cam & calipers handy at all times

*ducks & runs for cover*

God knows I can't even FIND my camera half the dang time...LOL

[billy]

Quote:       Originally Posted by big shrek

I don't have a pic to show the process, but one would probably assist many new shooters into understanding how it works...HEY BILLY!!! I trust Billy to have cam & calipers handy at all times *ducks & runs for cover* God knows I can't even FIND my camera half the dang time...LOL

[billy]

1.596
-0.291
______
1.305

[billy]

i have a big desk with all that kinda crap in one of the drawers so it is handy at all times!

[Rusty A]

So, theroetically, I could have a group smaller than the bullet?

[billy]

Quote:       Originally Posted by Rusty A

So, theroetically, I could have a group smaller than the bullet?

yes!
and i have done it more than once.

[billy]

here is an example.
single bullet hole 0.422

[Rusty A]

Thanks, billy, I've heard talk about groups that have been shot and the numbers didn't work by the way I was used to measuring.