The rangers all carried Model 29 S&W's, and one carried a 12-gauge pump loaded with slugs.

When they got serious about eliminating (not just moving) "trouble bears" they used .300 Winchester Magnums, as I recall. Though the Park Service wasn't very sophisticated back then about projectiles, but then neither were most hunters.

“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck