The OEM barrel that came in my Vet Long was excessively choked, even for a Veteran. It didn't have this burring right at the ends of the rifling though.
That barrel was fixed by aggressive polishing and fire-lapping. Since I didn't want to firelap the entire length, I did it this way.....Bare barrel (no shroud, no mod, nothing. Turn down the hammer tension to the point that pellets will just barely exit. I used some of the Seneca (Eun Jin) pellets with three essentially lube rings in the head of the pellet, thought being that those rings would help the abrasive stay between the head and rifling the longest. With gun decocked and no pellet in the breech I'd use a qtip to poke a bunch of 280grit Clover into the last inch of the barrel, at the muzzle. Then I'd shoot 5 or so shots, then repeat. Eventually it opened up the choke to the point that pellets measured groove to groove went from 0.211-0.212 (measurements before process) to 0.215-0.216 (measurements after process). And pellets pushed through with a rod still felt resistance, but not that absolute wall of constriction that was felt before the process.
As for results, it went from not keeping .22MRDs on an 8x11 sheet of paper @ 100yards, to keeping 95% of them under 1.75 @ that same distance. So I didn't make it an MOA shooter (I blame the pellets) but it did make it a usable barrel for hunting/plinking/pesting.