Short-Barrel Upper with Barrel Extension - What are the rules?

[Colonel Monk]

Howdy

Is there a problem with having a 12" upper with a barrel extension that makes the barrel's length over 16"?

Thanks,

Todd

[edgerly779]

NOT AS LONG AS IT IS PROPERLY PINNED AND WELDED. THERE ARE POSTS REGARDING THIS.

[Colonel Monk]

Thanks I finally searched with the right terms and found the definition of pin and weld.

CM