There is a very good chance that the difference is in the scales. Ask any woman just how trustworthy a bathroom scale is and they will tell you right quick that they lie, they lie, they lie.\
I don't have access to Gage pins but do have an inside mic. My barrels are really close to .438/.446. One thing I did do was to turn a brass plug to .431 and wrap it with SC 55 paper and push that through the bores. my finished barrel was nice, smooth and very consistent. My unfitted barrel does have a snug spot in it. Not to the point of feeling tight, but you can feel the resistance change slightly. so I am thinking maybe a change of .0001 or so. I don't know the age of the unfinished barrel I picked it up second hand. I figure the snug spot will not take much to lap out The finish on the unfitted barrel is batter than what the other was. It took a lot of work to get all the marks out of the other barrel but I did that and it came out good for the most part. It just took me a while is all.
Sam