wheelgun,you did not state the purpose of the gun,so I think any rechamber will not give you that much more than you are getting from the 7-30. You are only using a 12" barrel. Any thing based on a .444 marlin will get you more velocity,range and RECOIL. It will be louder too.
Guessing that you get 2300 or so from a 14" barrel you will lose around 100 fps in a 12".Going to a larger case will get you back the lost fps at a higher charge of powder . A jdj or super bower MIGHT be what you want.
The other option would be getting an encore in 7-08,this is pretty much what the super 7's based on .444 are.and is a hand full in a short gun! I have a Wichita bolt gun in 7IHMSA that I've used to kill whitetail and coyote's at beyond 250 yards. I am sure the 7-30 will be good for 200 + yard shots,so why beat your self up? NOT flaming ,just curious! jh
