.22lr with FMJ right around the ear(depends on broad quarter etc) will drop them on the spot, although they sometimes kick and squeal when you do it. Hollowpoints are not recommended, they tend to shatter on the skull and the brainscrambler of a nicely penetrated, intact FMJ is the best chance you have of taking one with a .22LR. I wouldn't feel good about anything over 50yd with .22 balistics. could be done, not particularly responsible. I have seen 4 piglets and a sow taken in under a minute with this method with a 10/22. Be careful of between the eyes, there is a real chance of deflection, even with higher calibers. Tree dwellers will not have this problem. I have taken 250+ lb hog this way. It is particularly nice for meat hunters. hope that helps.