Few weeks ago I called and talked with the ladies at NEF in Gardner, MA and was told the TDC barrels are available to add to an SB1 or SB2 receiver. When asking for the part# was told to just "describe" which barrel I wanted. Price is $82 or $87 (would have to find my notes) plus the $15 fitting fee. Of course if someone else has actually bought a TDC barrel through the barrel access. program would be more credible! :wink: