Welcome to the forum Long Time Lurker .I have joined up myself not that long ago , This is a great place and I'm sure you will enjoy your time here. By the way that's a nice rifle you have there .:)
My choice is the 6.5x55 my first use of this caliber was when I bought a Swedish mod 96 Mauser in the eighty's for 55 dollars along with the rifle came a couple of boxes of target ammo . I set up a target at about fifty yards fired one shot and then a three shot group .Three shots in one...