Thread: Rebore.

My understanding is that any existing caliber needs to be bored out first. This brings it back to a blank stock and then a button can be drawn through this. So a 243 barrel will need to be bored out to a new hole of say 249 & then rebore to a minimum 257. The grooves are usually 0.004 inch for a total caliber of 0.008 more than the original bore diameter. (For example 308 has a 300 bore & 7mm = 284 with a 276 bore.)

The late Din Collings once told me that a well used barrel would have a better molecular structure for reboring.