How do you measure your groups? Measuring groups properly?

[dustin]

G'day,

I'm obviously missing something here, one of you blokes will know though.

Watching some youtube videos on guys with bench rifles shooting super accurate stuff.

As an example, a guy shooting .308 measured his groups at 0.15"

How do you get a group smaller that your bullet though? .30 cal bullet = 30 cal group?

What am I missing?

Thanks.

[Baldrick314]

This happens when you're measuring centre to centre. The easiest way is measure the outside diameter of your group and subtract the diameter of your projectile. In this way it is possible to get a sub-calibre group.

I've ran into some people who disagree and say you can't have a group smaller than your projectile size but as far as I'm aware centre to centre is the standard for measuring groups

[Blackened]

I've ran into some people who disagree and say you can't have a group smaller than your projectile size but as far as I'm aware centre to centre is the standard for measuring groups

They're not thinking about it in the right fashion.

Dustin,

If you're shooting 30 calibre bullets you're right, the hole in the paper will obviously be 0.30 inches.

For examples sake, if you shoot 3 bullets absolutely perfectly through the same hole, your group isn't 0.30 inches, it's 0.

Think of the centre of the hole as your point of measurement. If the centre of that bullets pass through perfectly overlapping the centre of the hole there is 0 spread, 0 variation, however you want to word it.

Like Baldrick said, centre to centre. In the above example the distance from centre to centre is 0.

If the centre of the bullet passes through 0.15" from the centre of the hole, your group is 0.15. That's how your group is "smaller than the bullet".

Make sense?

[dustin]

Thanks Blackened.

Perfect explanation.