I thought the same thing when I went to pull my ring off (wanted to check it out for use on another project). I pulled the cotter pin, put the wrench on the nut (not much fits in there!), and put my 300+ lbs. on it. It moved pretty easily! In fact, I turned the nut about 1/4 turn, and was able to spin it off by hand! One quick rap on the side of the ring with the wrench and it broke free and pulled right out.
I know I just got lucky. If I had to do that in a GL yard somewhere I'd still be there trying to get it off! Oh, and my trailer is from the 60's.
Jim