Ok , I have been talking to a elderly gunsmith who worked at BSA in the old days (got BSA express sight & BSA sporter wreck off him too) & he said some of the low grades were made on Mil actions (he worked on them he said) they would build a sporter on a customers rifle too , he & I found in some of his old paper work a "Bush Patten" BSA Sporter with a 20in barrel like mine too !

I have some more info on shot out barrels also !