Is the .688 the standard barrel bore (i.e. the one that doesn't have the bore stamped by the thread)? If it is I'll check my kit bag as I think I have one.
Cheers
Rich
Checked with a mate who says the unmarked barrels are .689, is this the one your after? If you can confirm I'll double check, but I'm fairly sure I have one.
Cheers
Rich