Originally Posted by
gato naranja
I would never run a factory extension without the clamp. Besides ensuring the extension doesn't act like a brush/trash collector* or inadvertently act as a lever on those mag tube threads, it is extra insurance that neither the the mag tube nut or the extension loosens. Aftermarket +2 and +3 extensions also benefit similarly from a clamp to a greater or lesser degree, but in either case, takedown will require another step or two because of it. You pays your money and takes your choice.
I like the Wilson (ex-Scattergun Technologies) +1 extensions and ran them on an 870 for some time with no clamp and no problems whatsoever. I still have a couple of them in the Drawer of Yesterday's Shotgun Parts.
*Murphy's Law dictates that a thicket, stand of rushes, etc will manage to put something irritating between the barrel and the extension; the clamp doesn't prevent it totally, but it does limit the amount and reduces the distance you need to back off and/or pull out. Without the clamp, it can be like having a pronged flash hider or a tuning fork on the end of the gun.