The 720 was the Savage version of the Browning Auto 5, and there are or were extended tubes for that gun. I don't know for sure that they would fit, but that is where I would start looking.
Yes. Order for a Remington 870. It will fit (thread on) but not snug up the forearm. I am going to cut the original cap so its open, (to hold forearm in place), then screw on the extension. My +3 extension brought mine up to 8+1, even thou originally it only held 4+1. Know I need to cut the 29" barrel to 20".
Thanks bb, that is exactly what I was looking for. Ramline makes a synthetic for a browning A5 which is available on ebay for $59 which I'm sure will work with some minor fitting.