I probably killed more than 100 rats in a corn crib with a Crosman pellet gun running 500FPS.
I have no doubt you can kill a rat in your attic with Winchester’s rat shot cartridges.
And certainly a snake with their snake cartridges.
And I also have no doubt that you could kill rats with a Crossman pellet gun running at 500 fps. But that same Crossman pellet gun could also easily penetrate many sheets of wet newspaper, so I still laugh at the notion that a garden gun so anemic that it wouldn't penetrate wet newsprint would be good for shooting rats in an attic, or anywhere else. Nice try though, at attempting to recover from your silly assertion you made previously. It may have made an impression on those who don't know better.
I know this because after I advanced from homemade or Whamo slingshots, a couple buddies got Crossman pellet rifles. I spent a little more of my paper route earnings, and bought the more expensive Benjamin model 317 pellet rifle that would produce around 750 fps at full power. I still have it, and it has had the seals replaced a couple times. I used it last year to kill a bat in my shop. My Dad never wanted me to have a common BB gun because the steel BB's were much more prone to ricochet back at you or a bystander. In fact, he came home from work one day and saw me aiming my slingshot at some pop cans by lining it up with my eye. He told me you never aim a slingshot like that, because if the band broke, it could injure your eye as it snapped back at you. He then took my slingshot and proceeded to knock down several cans in quick succession without missing once, by aiming or pointing instinctively with the slingshot at chest level. That was one of many great lessons I recalled yesterday as I thought of him on Father's Day. I'm sure he probably hadn't touched a slingshot since he was a kid.
We shot all manner of vermin, birds, and critters, and expended many thousands of toxic lead pellets at various targets. And we even mimicked the gun writers of the day by doing penetration and expansion tests on wet newspaper bundles, wet phone books, wet Sears catalogs, apples, tomatoes, water filled pop cans, etc., since nobody was using ballistics gelatin back then.
I'm pretty sure that if ballistics gelatin was used back then, we'd have gotten in trouble for pilfering our Mom's cupboards for boxes of Jello.
One nice thing about those pump-up pellet guns was that you could vary the power by the number of pumps. So of course we learned that a pellet at very low velocity not only wouldn't penetrate many sheets of wet paper, and had a rainbow trajectory... but also wouldn't kill anything except things like grasshoppers at spitting distance.