Honestly, I think birds on cattle farms tend to be heavier than woods birds. My hens love to feed under the calf creep feeders. Although I've never seen the gobblers using them in the spring much, they do seem to like to hit them when it's not breeding season. Our birds average around 21-22lbs on fish scales, but my personal heaviest was 26lbs. My cousin has taken one that was 27lbs (fish scales), and our largest bird weighed 29.5lbs on certified scales (this is out of approx. 200 birds taken in past 25 years). Unfortunately, one of his spurs was broken off and the other partially broken down to 1 1/4".
They also LOVE to pick the undigested corn out of cow patties, and leave no dried pattie unturned looking for grubs, worms, and beetles underneath them.
Of course, that doesn't count the 35lb'er I killed back in '95 than ended up being a domestic bird belonging to a neighbor 3/4 mile down the road- oops. I still feel bad about that one.