Barrel compatibility?

[C-Fish]

I have a stag 2HL (lefty) 16" Carbine upper.

I'm wanting to build a SPR upper (18" 1/7 Mid) and wondering if I can just swap out the barrel?
This would save $$ over buying a complete new upper.



Someone mentioned making sure the new barrel has an "Ambi Extension"...



Thoughts?

[Todd.K]

You do need a Stag Ambi barrel extension.

[C-Fish]

Thanks Todd...