World of the Hunter

Mulveen had come to Earth for a big-game thrill; it was up to Gilbert to provide it for him—even if he had to let himself be stalked!
Gun, boy! Mulveen cried.
The big saurian—a thirty-tonner, at least—came splashing and bellowing out of the swamp. Gilbert quickly brought up the archaic Earth rifle, ramming a shell into the breech with the bolt-action loader. With almost the same motion he thrust the big, capable weapon into Mulveen's waiting hands and the hunter brought it to his shoulder without a moment to spare.
Actually, it was an adapted old big-game rifle: the shells it fired were atomic. Standing his ground weaponless, Gilbert saw Mulveen's finger whiten on the trigger, saw the scale-hided saurian grow immensely before them, heard its surprisingly high piping challenge, then saw and heard in one quick flash of suspended time the roar and smoke of the big rifle and the sudden life-ending, sleek-scaled, column-legged death-rearing of the big saurian as it came upright, the piping a high death scream now, the small forelimbs tearing at air, the head with the very tiny hole between the eyes swaying as if drunk from side to side, the long, muscular, five-ton tail still thrashing in the swamp waters.
Then the saurian came down, crashing through the brakes. There was only a trickle of blood, but the bullet, like a Dum-Dum of three hundred years before, had exploded inside the monster's head, the minute atomic charge destroying everything within the thick bone walls of the skull but leaving skull and metal-tough skin intact.
Time flowed again. Mulveen returned the rifle to Gilbert and waded forward through the brackish water, his hipboots glistening.
Beauty, isn't it? Gilbert said with feigned professional enthusiasm Mulveen needed the enthusiasm: the big humanoid from the Sirian system had been a grumpy, fussy, dissatisfied hunter throughout the safari.
Don't try and dun me for a tip, Mulveen snapped. You get paid whatever the Earth company pays you. He was a big, bald man with a florid face, an amazing girth of shoulders, a barrel chest and almost pipe-stem legs which seemed barely able to support his weight.