Hey everyone, I have an older Mossberg 500, mid 70's. I bought it to make a HD shotgun with it to place my H&R as a backup. I had an 18.5 barrel already so I have been using that on the shotugn but I really like the look of the 20" barrel and extended mag tube. I have as it stands a 5+1 mag tube and want to increase to at least 7 round mag tube. Looking at the way the barels fit with the mag tubes I dont see a 7 round mag tube working with the 18.5 barel. Normally I would sell my shotgun and buy a 20"HD shotgun but since I have this shotgun already is there a way to convert it to 7 round magtube or a place to get parts that would be in stock to convert to a 20" set up?