I posted this on the genreal board but thought that ya'll might not get over there that often. In the Current issue of the Marine Coprs Times (dated 28 October) there is an article about the testing of a Designated Marksman rifle.
The Photo shows a Flat topped A2 (A3 I guess) with a Knights FFRAS supported by a Harris bipod. The barrel seems to be a 20 inch HBAR with a standard flash suppressor. The gas block looks like a tall and long Armalite block that has a bayonet lug. I have never seen anything like it before. On the Gas block there appears to be a knights flip up front sight. The optics are an ACOG (TA31) mounted in an ARMS 19 ACOG mount.
The article details the idea of placing one of these rifles/rifleman in every squad. Something along the idea if the Israeli Designated Marksman program. Currently only the 4th MEB uses such shooters as SOP. Very Interesting to be sure. I wonder if this is the Marine Corps SPR A? Sorry I don't have a scanner to scan and post the photo.

IPSC_GUY sends

Look at this article on the new/current M14 DMR:
http://www.usmc.mil/marinelink/mcn2000.nsf/ac95bc775efc34c685256ab50049d458/ab0dd7f5b0776c8585256b4200426474?OpenDocument

Here's a pic with a DM class with the rifle you talk of:
http://www.usmc.mil/marinelink/image1.nsf/ae82f18a8e1b160b852568ba007e7e5e/685a23c8e143d2f785256b600065bc3b/$FILE/Marksmanship%201.jpg

The gas block looks like a front sight base milled down to what you see.  The front flip-up sight is attached to a floating-tube type handguard with 4-way rail system on it.