I have some casings I picked up at the range and I cannot figure out what round it is. Looking or some help from someone with more knowledge than me! The casing is short in length than 30-06 and larger than .308 and has markings on the bottom 12 and 55 with two stars dividing them? Case neck mics out at .323 or 8.25mm and length is 2.23'' or 56.7mm