I have inherited a browning a-bolt in 270 cal. I would like to change to a smaller cal. more sooted to varmit shooting on the farm. ,ground hog,fox,coyote) As these guyes have all been shot at before, will need to be able to take 200 + yard shots. What can this reciever be rechambered and/or rebarreled to,cal.), and use an economical, easy to reload cal.