edge bales are almost always heavier for us - more weeds, often shaded by trees so it doesn't dry as well.
So we'll start baling the outer edge, but expect the bales to be heavy - so we don't pay much attention to them.
once we're in a row or two we just stop and pick a random one or two up - see if it feels "right".
About 50 lbs.
I've never weighed one, never seen anybody weigh one. Not even horse people. (though I'll bet they do when we're not looking)