I've killed a few hogs in my day and the biggest was estimated to be 225. 3 of us estimated the weight and 225 was the lowest, so that's the one I use.
Shot the hog while crawling on my hands and knees thru a thicket. 12 ga 3" 00 buckshot at about 20-25 yds.
I don't believe I've ever seen a 300 lb wild hog. Not saying they aren't out there, I just haven't seen one.