I agree with OSO......a .22 short would work under the right circumstance......at short range, a 220 grain would most likly be running around 2400 fps..........while external ballistics are not certain, some testing indicates the best penetration and expansion occurs from 1800 fps to 2500 fps......any faster and the bullet tends to come apart......move the hog out a little farther and I'd pick a 180 grain.......
A 150 or 180 grain would certainly do the job, but might tend to over expand.......and as a result under penetrate.....unless, of course, it was a Barnes........right Redhawk1?
Hey......if the 150 shoots good then I'd use what I felt comfortable with.....there is no right or wrong, just personal preferance......which, for me..on russian boar....at close range.......would be the trusty old dusty 45.70......as it makes big holes.......while penetrating well.......that doesn't mean another guy might like a .17HMR, or a slingshot......