I am putting together a long distance(300 to 600 yard) ground hog rig. I have a Savage 12FVSS in 300 WSM that I just restocked. I want to use this platform for my new rifle. Here is the problem. The 300 WSM is shooting .25 inch three shot groups with a 155 grain bullet. The second part of the problem is that my AR has ruined me-the AR has allowed me to see impacts and I really like that. The third part of the problem is that whatever I do to the 300WSM barrel I will not be able to see impacts(and the 300 WSM is a little large for ground hog's). I have posted a MB post on a couple of sites-and the consensus is that I will not be able to see impact's. I was going to re-barrel the 12FVSS to a hot 22 or 6mm cartridge. The problem is that would require a different bolt face. Now I know that the bolt face can be changed, but then I would loose the ability to put the 300 WSM barrel back on as a switch rig. Now my question. What cartridge can I rebarrel to that will allow me to leave the rifle as a switch barrel rig, and use the same boltface?? I want a hot fast cartridge for a varmint rig?? I will be putting a brake on the barrel, and I want to be able to see impact's?? This may not be possible, but if it is possible I am sure one of you guy's would know about it. Thanks, Tom.