GunnSmokeer
Senior Member
Explain to me how this fits in.
“Therefore, so long as a parts kit or collection of parts ..."
The reason is simple.
If you have both a shoulder stock AND a 16" barrel, it's totally believable that you only intend to use both of those things together to turn your pistol into a rifle, and then return it to a pistol by taking BOTH of those things off at the same time.
If you ONLY have a shoulder stock for your pistol, and you don't even OWN any rifle-length barrel for that gun, the only plausible reason for wanting that combination of parts is to be able to quickly assemble yourself a short-barreled-rifle.