Let's talk SBR legality here for a minute

Faktory 47

chance

Tracker
Jul 15, 2015
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There's no such thing as a "permanent change" to an AR lower when it comes to barrel length or caliber.
Exactly. Thats why I wouldnt notify them for an AR.
Do you literally just mail them a letter? Not like an official form...
Yea just mail the NFA branch a letter with the pertinent info (trust name, Serial, etc) and let them know that caliber or OAL changed.