The Carbine as SBR

[Captain O]

Cuidado: You had best measure your barrel before cutting. Many of the carbine barrels are 17.75". Shortening the barrel a tad too much could draw too much attention from the ladies and gentlemen at the Federal Alphabet society, (BATFE, FBI et. al.).

[tenOC]

Don't those interested parties measure by inserting a dowel into the bore to the bolt face? I've had two barrels come to me shortened to 16-1/4" and 16-1/8" outwardly measured, but when inserting a dowel and measuring it to the bolt face they were longer.

[Captain O]

I have seen those dowels, but i wouldn't trust them. Perhaps they're okay.

[tenOC]

..because now we're speaking about legality, exposure and interpretation by humans by these parties and all humans/individuals have failings? At local shows those operatives are typically on site and I've seen attempts to lure people into discussing illegal activity, or even engage in it by trying to buy an item moments after it was purchased by a private party, which is supposedly not allowed.