I've never been too impressed with rat shot.
For one thing, it's pretty weak. It won't break a beer bottle, for instance.
"But will it kill a rat" you might ask.
Well, that's the second problem.
Trying to get a shot on a running rat you just scared out of hiding is not easy. you will get about two seconds at the very most before he's gone, and the little bugger won't run in a straight line at all.
Lead him? yeah, right. just as soon as you tell me what direction he's going to run, I'll get right on it!
I've tried it several times and had ZERO luck.
Sniping the little thieves is easier, and can be fun too.
Get some dry dog food and feed them for a couple of days in a spot you can shoot from hiding.
A pellet gun will work, but it needs to be a pretty good one.
I shot several with a Crossman 177 cal pump up, and had them run away.
That's fine if all you want is dead. They probably only went a short distance before they died.
If they run under your house, however, their stinking carcass might cause problems.
I shot this one with a .25 cal Beeman, and he died right there in his tracks.
I say forget the rat shot, and the ambush hunting styles.
Snipe those suckers with a good pellet gun and have some fun with it!