Dave,
I'm not sure what your pictures are suspose to represent poor welding or poor workmanship on fitting of the barrels. Either way they are not even close to one done the right way.
The barrel on the bottom does not have enough dwell time on the lower lug. The way it's cut it would make the gun out of time and respond like a blow back action. It also appears to be bent.
The top barrel is not quite so bad but it appears to not have enough material in the feet area of the lower lug for a good lockup and the link appears to not have enough clearence to clear the radius of the lower lug.
I've seen high quality match grade barrels that looked as bad as the two you have pictured all because the people that were trying to fit them did not know what they were doing.
Regards
Bob Hunter
www.huntercustoms.com