The case dimensions from the base to the shoulder are very similar for the .243 and .308. Not so with the .22-250 in a .300 chamber. I think there might be a little wiggle room to allow the laser beam to be out of center with the bore. You might be able to shim it to keep the base push back to set flat on the bolt face. Just thinking as I type...I have not use one of these units.
