I've got a 116 in 338WM and I have been splitting a substantial amount of brass (2:5 ratio of split to not split). Out of 70 reloads, 20 have split necks. Some are single splits and others have two or three splits. This brass is once-fired, though it is about 16 years old. My two brothers and my dad have all shot brass from this lot and none of them are experiencing this problem. They are shooting 73 grains of IMR 4350 while I am shooting 72 grains, both behind 225 hornady sp. My COAL is longer (3.374) than theirs, but is still short of the lands. Why is this happening? I've tried googling, but split necks almost always leads to something about cases being shot 10 plus times. Could my chamber be too big? I need to get this solved!

Thanks

jb