Im wanting to build a clone, or close replica, of my M16A4 SDM-R that I used in the Army. I have most everything figured out except the barrel and rail system.
One thing I dont knw though is what rail system that my rifle had. It was a free float system. I have some not so good pictures but I cant tell what they are. Sorry for the dumbass in the pics.
I think they were DD M4 rails with fluted Douglas barrels with rifle feed-ramps. I also think they had KAC 2 stage triggers. I’m 90% sure the FSB was secured via 4 set-screws also.
How concerned are you with it being an exact replica? I’d honestly look into a pinned FSB, and ditch the KAC trigger for a Geissele. It would have the look and feel of the original rifle with some functional improvements.
Mine was a solid sub MOA rifle when shooting M262. But it wasnt that easy to shoot near its limits with the 4x ACOG. Your typical M16A4 is probably about a 2-4 MOA rifle when using standard ammo.
I never had a problem with my rifle. Being that the only real difference was a stainless barrel, free float rail and trigger I dont think you would see much if any loss in reliability. The match barrel does have a differnt chamber so that could possibly make a difference but I dont know.
Thanks for the info. Guess I didn’t think they would be that much more accurate using issued ammo. I have found similar 2-4 moa results out of my 16" and 20" rifles using your typical ammo.
A build like this has me interested as I currently have a 20" A4 upper on one of my rifles, but find myself never using it because it doesn’t shoot any better than my 16" middies do. I had looked at building a WOA 20" service rifle upper recently, but figure that would also not get used much. I had not given an upper like this much thought until just now.
Oh, and browsing elsewhere on this forum I just found this upper. Not sure how much it interests you, but it looks like a solid choice for a rifle in this category.
Weapon System Description.* The USAMU prototyped the Designated Marksman Rifle using the same technology for building National Match M16 competition rifles.* The USAMU Custom Firearms Shop removes the GI-issue chrome-lined barrel and replaces it with a heavy profile stainless steel match-grade barrel with 1-7 or 1-8 rifling twist.* The barrel has twelve flutes machined into the portion of the barrel covered by hand guards or the for-end rail system to reduce weight.* The front sight base is installed using Allen head screws vice drift pins to prevent barrel deformation and to provide windage correction when the iron sight on a standard M16A4 carrying handle is set to mechanical zero. The Modular Weapons System accessory rail is removed and a free-floating rail system is installed.* Free-floating provides consistent shot-to-shot accuracy, as the barrel is not affected by sling tension, firing position changes, or vibration changes from bipod pressure.* The free-float rails allow the Soldier to attach all standard accessories to the rifle, including optical, thermal, and Starlight sights; telescope; Aim point; the AN/PEQ-2 Target Illuminator/Pointer, and the AN/PAQ-4 Infrared pointer.* The standard M203 will NOT mount to the free-float rail (this requires a USSOCOM rail quick-attach M203).* The USAMU provides a modified Harris bipod with quick-detach hardware to fit on the accessory rail.* The standard blank adaptor fits the GI muzzle compensator.
Understood the rails where Knight as whee the triggers, depending on which document I look at. Seems like the barrels were Douglas.
Ehhh…I’m functionally certain, as in 99.99% sure, that the standard rail for these rifles, and the one pictured in the OP, is a Daniel Defense M4 Rail.
I have built several of these using WOA and Superior Barrels (Douglas blanks profiled by CLE) and have had great results with every one of them. If I had one thing to change, however, it would be to go down to the 1/8 twist since it stabilizes the 77gr just fine.
The only issue I have with the BCM is that it needs to be bead blasted to get a good surface for the paint to stick.
