Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is an old low-budget hour-long western of the kind that probably played all day long in theaters full of young boys, at least until they were diverted home by television.
The rattlesnake part of the plot is drawn out throughout the last half of the movie. We see a man, one of a gang of cattle rustlers, with a wooden box containing a rattlesnake that he just caught and plans to keep as a pet - "he's a nice one, big fellow too" with "lots of buzzers. I'll tame him." The boss of the cattle rustlers, Luke Todd, tells him to keep it away from him. He says this a few times, foreshadowing what happens later. (If someone expresses too much fear of a snake in a movie, they generally get in trouble because of a snake later.) But the newly-hired cook tells them he'll make a stew out of it. He describes how to fix rattlesnake stew - first you get a rattlesnake, then you kill it, skin it, boil it, and add vegetables, "...and if you don't die, you got a durned good stew."
We see people looking at the box a couple of times to remind us that it's still there, and at the end of the movie the snake finally appears. Todd tells his henchman Pete that he's going inside the cabin to get the drop on Trigger Carson (Harey Carey) who is working for the law to catch the rustlers, and when he leaves through the back door, Pete should let the rattlesnake loose through the front door to kill Carson. Of course, it doesn't go as planned. Carson knocks Todd down and ties him up then leaves through the back door. That prompts Pete to let the rattlesnake loose in the cabin, so he does, with lots of loud rattling sound effects, and the snake bites Todd. Todd even talked to the rattlesnake, telling it he would not move because if he did the snake would bite him, but he forgot that snakes don't have ears and probably wouldn't understand English if they did. Carson goes into the cabin and shoots the snake, then the town lawmen enter just in time to hear Todd say that he knows he's finished from the snake bite and confess his crimes. He dies only a couple of minutes after getting bitten, in a completely unrealistic manner used in most movies which has helped to demonize all rattlesnakes through misinformation.
The live rattlesnake in the movie is either a Western Diamond-backed Rattlesnake or a Red-Diamond Rattlesnake. It's hard to tell in black and white.