We've discussed this before, and I think the answer is they're all pistol frames and are sold as such, regardless of which configuration it was made into.
Edit: I took this question directly to Smith & Wesson last year, so I went back through my email inbox to find it. This was their reply, shortened: "... left as a rifle in 209x50 rifle configuration, but they both will be considered pistols per the ATF since they can become pistols."
Edited by TN Lone Wolf (09/29/16 09:03 AM)
Edit Reason: Add
Formerly TN Lone Wolf
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