I have a Sako 75 in 6.5x47 Lapua. I don't know what it started out in life as. I want an extra magazine and have found (not cheap) them for 243/308 and a separate P/N for the 22-250. My current mag has no markings or P/Ns on it. Which mag should I get? Does the 6.5x47 L case more closely match the 243 case or the 22-250?