I'm putting a new stock on my 20 ga 686 Blackwing. The new stock (older) fits perfect but the bolt from my Blackwing is too short. Apparently the stock that I'm trying to fit takes a longer bolt. Old bolt is 6 1/8", the bolt I need looks to be about 7 1/8". I've looked all over at the internet but all they list are new parts and short bolts. How do I find one of these older longer bolts. Any suggestions. Thanks. Jim