I've always wonder why Savage used that head dimension! But back when the .35 was introduced the ".30-06" head-size hadn't quite become standard. (Actually, the "standard" .30-06 head-size is actually 12mm, the diameter of the 8x57's head. But that's another subject.)
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.” John Steinbeck
