Only once have the standard Weaver rings fail to keep a scope in place, and that was many years ago when some scope company sent me a VERY heavy 30mm scope to test for a magazine review. The only 30mm rings on hand that would mount it high enough for the bolt handle to clear the big ocular lens were a set of standard Weavers. The scope didn't actually slip during recoil: Instead the "hook" side of the ring caps would jolt loose after 2-3 shots. Eventually I had to buy a different set of rings for the test.
Other than that, I've been using 1" scopes up to perhaps 16 ounces with standard Weaver rings on rifles for several decades, and have yet to have a scope slip inside 'em. The rifles have included quite a few hard-kickers, from various .300 magnums to a relatively light .416 Remington.
