BAR Detachable Magazine (got some interest so I'll post instead of PM)
*Must be a Long-trac or Shortrac. Same receiver set-up as Winchester SXR
Long action detachable Floor plate for a Winchester SXR # U3177046F4
Short Action detachable Floor plate for a Winchester SXR #U3177043F4
Must come with Spring (#B317620801) and pin (B317671002), which they should.
The floor plates are $15 each US, but to get them you have to go through Western Gun parts in AB and they will charge you $80 for two shipped. You use your existing metal box mag with the floorplate. I epoxied the box mag to the floorplate because sometimes they come apart in your pocket. The other option is to buy a Winchester SXR detachable mag for $100.
Remove the front forestock. Punch out the pin holding the hinged floorplate in place. Remove hinge floor plate. Re-install pin. re-install forestock. Very Easy.
I have done this conversion a few times, only with long actions. But the same Winchester Tech told me the part numbers for the short action floorplate and they should be right.
You can also drill out the stopper (5/16 and de-burr) on the mag so it will hold 5 rounds instead of 4. This is only good for open bolt reloads, as there is no extra room to insert a full mag of 5 into a closed bolt.