It seems like our decades old Walther KK200s might have been 'chassis rifles'.

Eh?

To me, a rifle chassis is a stock that allows the receiver to be mounted with no modification to the stock, and no need for bedding, with a free floating fore end.
Able to accept detachable box magazines, with adjustable length of pull and cheek riser.

Very much a drop in "plug in and play" approach, compared to not so long ago when one would need to have the stock bedded to the action, and then inletted to accept whatever DBM system was desired.

Any system that replaces what would otherwise be a classic wood or fiberglass stock with any system that has an aluminum inner skeleton from front to rear in which the receiver is secured in some manner by one or more bolts or screws. Such systems usually make the rifle modular in some fashion by means of interchangeable stocks, cheek risers, addition of Picatinny rails or any bolt-on rail system in the forearm area or under the buttstock area for the attachments of scopes, lights, bipods, monopods and vertical grips.

Although most chassis systems don't require bedding, I have modified some chassis systems with bedding to tighten up areas around the receiver which affect accuracy (the heel area of a M14).

Tony.