[BUCKSHOT]

One of my favorite pistols is a browning h/p which I bought new in 1975. I've shot it at least 2 thousand times without any problems with the exception of the rear adjustable sight lost a screw and spring (elevation). Come to think of it of all the brownings I own and have owned that was the only problem. I used to do a heck of a lot of shooting when stationed in Port Canaveral. I used to carry an old .45acp that had been tuned and that baby could shoot. It was so good that I could load the mag. with the empties and hand cycle it and it would feed and eject about 90% of the time. I shot it so much that it started shooting low and over the years had to keep filing the front sight down. Finally I took it to a .45 smith and he installed a new bbl, bushing, link and sights. Guess what - it still shot low. I surmised that the bbl. lugs had worn down causing the bbl. to point low. Don't know what else could have caused it. Finally had enough and sold it and had another one built.

 

[Flyer]

The barrel lug recesses in the slide may have worn down... but if a new barrel was installed, it should have been properly fitted to fit higher into the recess for proper lockup. Point of aim should have been fine.
There's also the possibility that the takedown pin/slide lock had worn the frame holes... which could also cause a different POI.
In any event... if your 'smith installed new sights, he should have corrected the problem with THAT method, since your pistol seems to have been a winner in every other department!
Flyer