Hey guys. I am looking at building a rifle in either 300 WBY or 7mm STW. I am looking at basing it on a Stevens 200 long action then throwing a Shilen barrel on it. Since these 2 calibers have a very long COAL, I am wonder how long the action opening is and how long the magazine box is. Also, am I able to use a standard shank size for those 2 calibers? Any help would be great. Thanks.