My understanding is the the rear lug on M14/M1A receivers mounted in a bedded stock slightly increases the longevity of the bedding material as the recoil forces are absorbed over a larger area, but it doesn't improve intrinsic accuracy per se).
(I read on the first thread on this sub-Forum re DMR's that the USMC DMR's actually had a rear lug added, which I found interesting and hard to believe given these are USGI receivers, but that's what Marty of Badger Ordnance indicated, which makes cloning a DMR a bit more tricky. If I had to do it over again, I would have bought two of the 18' barreled versions, and used them for what M14-based actions are really. Dont get me wrong, they were excellent rifles, but didnt fill the niche I bought them for, which was as a precision semi-auto platform. I got the impression this 2112 was not a huge fan of chassis systems.just an fyi. I had a couple of LRB M25s built up by Smith Enterprise. BTW, the 2112 who gave me the run-down on all these PWS-built rifles (& pistols) stated that during accuracy testing the DMR rifle was more accurate than the M39, likely do better bedding of the stock. As noted by Game Warden, the scope used appears to be the 10x fixed version, at least that appears on the DMRs built by PWS for the fleet, with a few specimens like this one are kept in reserve for future training and support purposes (as shown in the attached pics). Stevo86, here's a couple of pictures of a PWS-built DMR M14 and M39 taken during my recent visit to the PWS building at Quantico (June 2016).