Can the accu-stock barrel channel be opened up from sporter to hvy. sporter .685 muzzel? Didn't know if it is hollow and will end up with a mess on my hands.

Don't have the gun to work with yet, but would like to drop in a Shilen 260 AI hvy. sporter barrel. Are the barrel channels a different size for the different sporter calibers? That would make a difference on what to start with.

Thanks in advance.