Glad to see you got it to fit properly!
One rule of thumb I would recommend, and I've fitted several barrels, and although I'm not claiming to be an expert by any means, but my rule is never ever mess with a receiver trying to get a barrel to fit. I know you didn't do this, but this is for anyone else trying to fit one. Doing so will only open a whole new can of worms. For one, the receiver has already had a barrel fit to it, and that original barrel should you still own it, will then not fit properly, and altering the receiver will mean you may continue to have difficulty trying to fit another additional barrel to that receiver without replacing parts you messed up, and you can cause headaches to the next guy who might own that receiver should you sell it.
Rather than getting to the point of attacking the receiver, one might consider sending it in to have it factory fitted like Tim suggest, as it doesn't cost that much to have it done right.
In most cases that I've found it's number one, the hinge pin radius on the barrel lug, just as you found, and once you get the barrel to seat down all the way and lock up, then you can play with the latch to make sure it locks up evenly, and then it may require you hit the latch shelf and maybe the breech face on the barrel lightly with a stone also, but that is usually only after firing a few rounds and if you start getting some consistent pop opens with a dry, oil free latch shelf.
Again glad to see you got it fitted, and for some reason I can see a lot more used barrels in your future!
