Model 700™ Varmint-Tactical Rifle

[Cappy]

It's sometimes just easier to measure outside to outside then subtract the bullet diameter to get your centre to centre measurement

 

[acrashb]

Edit: Or does the tool make an allowance for the bullet diameter?

Most electronic calipers (including the one in the pic, see the "zero" button) can be zero-set anywhere in their range. So you would open the calipers to .224, zero them, then measure edge-to-edge. The number you get is your centre-to-centre.

Looking at the targets, I don't think that manitou210 has done it that way.