Don't mean to hijack the this thread but thought I'd give an update in case anyone else is in the same boat I was in.
I bought the replacement spring listed in the ebay link and a new factory magazine (BC not BC2) from Midwest Gun Works. The spring worked but the magazine did not. The BC2 and BC magazines appeared to be identical but I could not get rounds to feed from the BC magazine. Not sure what the difference is (other than being for a Winchester vs an FN rifle).
Thanks again for the tip ElkSnort.