LWRC (formerly Leitner-Wise Rifle Co.) has built one for a customer (16") that was very successful. I posted a link to a video a while back showing it being shot for the first time with a suppressor. It was so quiet that the shooter, the LWRC VP-Engineering, thought that it had misfired.
http://media.putfile.com/LWRC2
I am having one built with a short (7.5") barrel that should be completed in the next couple of months. There will be some features that I'm not sure if I should mention at this time, but you can call Darren at 703-455-8650 for more information. I'm a shareholder and get information that is not public and do not want to spill the beans before they are ready.
LWRC has so many projects in the works for the military and preparing for SHOT that mine is on a back burner. They will eventually be marketing it as a 300LW, but I do not know when they will be available for sale. There have been vendor issues but LWRC plans to eventually make nearly everything in-house (except barrels, which will be supplied by Lothar-Walther).
POF-America should work just as well, and I believe they are available off the shelf. Just need a barrel and possibly and adjustable gas block.
E-mail me if I can answer any more questions.
David