.665 seems to be a good starting point for most loads in a RemChoke barrel. Some loads do better through a tighter choke, but .665 is always a good place to start out.
The best range for most RemChokes seems to be about .655 to .670
However, it appears that SumToy makes a dandy .650 choke.
Those LongBeards sure are doing the deal. It almost doesn't matter which choke you use.