That is the stock used on the old Iron Brigade Armory built XM-3 rifles developed for DARPA in the early 2000's, and used my Marines for years in Iraq before they were worn out through constant usage.
Old school Marines wept when the Corps traded in the old "iron and wood" M14 rifles and old school Marine sniper wept when they turned in the A1 stocks.....
When rails are put on rifles people want to put things on those rails: I need a light, I need an IR laser, I need a coffee grinder....and so on. If you are crawling/stalking through dense vegetation those rails get caught on everything, you want something that will glide through the terrain, not tug and pull on things and leave signs a blind person could see, or make enough noise a deaf person would hear.
If you are just punching paper on a range, it is great: it's light enough to handle easily, but heavy enough to help keep recoil down a bit. I have one on my IBA XM-3 and love it. I would recommend one to anyone who is interested in a quality stock that gets the job done.
Just my .02 cents
IBA is still building rifles for serious collectors/customers, if you're interested, let me know and I can contact him.