If it doesn't lock up and fits tight, it may be pretty easy to fit it yourself.
You shouldn't have to worry about shimming and once fitted it would be like a factory fit.
Try smoking the latch and see how much if any if the latch catches at all?
Sometimes a light stroking with a stone on the latch shelf is all that's needed. and if it's really tight, you may need to sand the pin pivot on the barrel lug.
It's always better and easier to fit a barrel that you have to take some material off of, than to have to put it back with a shim or epoxy.
Check the FAQ's on barrel fitting, and just take it really slow and check the fit often. Slow is the key!