Best left to a gunsmith
Remove the butt plate and you'll see a hole. Down the hole is a nut on a threaded rod, holding the butt onto the gun. Remove the nut = remove the stock.
The only way to know for sure is to try. It should, but, may require fitting.
To remove the trigger guard from an older browning bar you unscrew the butt plate from the stock. Then you need a long flat head screw driver The stock is removed from inside the stock . Once stock ios removed the trigger guard can be removed by sliding backwards. Hope this helps
Best left to a gunsmith
The butt plate screws (2) at the end of the stock must first be removed. You will need a long shank flat tip screwdriver to remove the screw at the bottom of the center hole in the stock butt. Reverse to reassemble.
There are two small holes in the butt pad of the stock. Lubricate a Phillips head screwdriver into the holes and remove the butt pad. Using a long flathead screwdriver remove the screw in the center of the stock. To add new stock simply reverse.
Recommend you leave this to a gunsmith.
Best left to a gunsmith
Try e-gunparts.com or MidWest Gun Works.
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ebay, gunbroker, Brownells, Midwest gun works - all on line
I have a used "riot" 520-30 butt stock.