I am going to rebarrel a rifle to a 300rum, Here it is. How long? what twist? I will be shooting a 180 gr bullet. Muzzle break or not? What barrel. what conture. I am going to be shooting 200 to 600 yd. I have not settle on a 300rum. any other suggestion 8mmX30? let hear it. By the way I am a newbie. First post, my name is Jeff Rutledge.