I used an old 10 spd chain on my restored Raleigh Super Course 6 speed. I was in a hurry to get on the Pasadena Retro Velo ride, and couldn't wait for the new chain to arrive in the mail. I couldn't find my new break-off Shimano pins, so I reused the old pin. I've done it a few times before, with no issues. This time I made it about 4 miles into the ride, the pin worked loose and jammed in the rear derailleur, stopping the pedal action immediately. It took awhile to figure out. I started walking back to my car, and saw a big rock on the road, so I used it along with a wrench out of my seat bag as a backstop, and got the pin back in. I rode gingerly back to my car. The new chain arrived next day in the mail.