I'm looking at putting together an XM177 clone for my next upper.  I don't want to permanently attach anything, and want to keep the 16" all barrel.  I have a slipover flash hider to give it (almost) the right look.
Anyone know where I can find one of these barrels?  TIA.

You probably know this already, but here it goes.
look at the bushmaster online catalog, they have a superlightweight 16" preban pencil A1 barrel, but it is not 1:12.
1:12's will be hard to come by, you'll have to keep your eyes open on the auctions.

Yea, I've seen that.  Thanks anyways.
I want a 1:12 because I want to use this upper to be convertible to use with my Ciener 22lr kit.

M-4 Guy,

Check with Fulton Armory.  If I remember correctly, a couple years ago they were offering their millenial or millenium rifle in either 20" length or 16" length.  The 16" length was similar in appearance to Bushmaster's Dissipator and used the full length handguards.  Anyways, both the 20" and 16" versions of these were made from A1 barrels having not only the pencil profile but also the 1:12 twist.   Perhaps Fulton Armory could still set you up with what you want.