The current ones do not, they have heavy barrels.
I'm trying to remember if the older 6601s had gov't profile barrels but I don't this they did. If I remember correctly the 6601 was the "Sporter Match HBAR" and therefore should of had a heavy barrel from the start.
Edited to add: a quick check of biggerhammer proves that my memory isn't so bad after all! The 6601came with a HBAR.