Mauser...When you say the screws for the bases just spin...Are you talking about where they screw into the top of the receiver??? I hope not, it might mean they have to be drilled out and re-tapped for a larger screw....

My little brother (he's 48) picked up a 700 in 22-250 on a trade a few years back, his groups the Remington 55 grain Soft Point well...His daughter
(16 now) has killed several deer with this gun in the past few years, using the Federal Premium 60gr Nosler Partition, groups with this bullet run about 2 inches at 100 yards, but most of her shots have been within that range.