Recall that I told you “that Rock River Arms, Knights Armament, LaRue Tactical and Daniel Defense isn’t the Colt produced under milspec for the Army and Marine Corps (these are all superior to the Colt M-16 and M-4)?”  And recall that John Jay and I have both discussed Milspec and what it does (and doesn’t) mean?  And at Western Rifle Shooter’s Association I have had this discussion in even more detail.

While some features of some AR-15s (that don’t match Milspec) are positive, like the Wylde chamber which is highly acclaimed), some not so much. For example, RRA uses red Loctite on the Castle Nut, a feature many guys who do their own build don’t like much.

Listen, as an engineer (PE), I can tell you how I would approach it. I would take several rifles from different lots and measure the crap out of each and every tolerance (including head space, chamber, leade, etc.) before passing the design and saying it met my specifications. If I say that some specific part used SS304, I would send that part out of rifles with different lots to be melted down, and a spectrographic analysis done to determine if the Mn, Cr, Co and other elements were within tolerance. One slipup means the whole lot gets rejected.

And that’s the way the mechanics and engineers at the Picatinny Arsenal will approach it too. Milspec means something very specific, good in some instances, perhaps not keeping with current design improvements in others, but simply meeting the original order specs sent by the engineers.

Well, the Marine Corps is upgrading their rifles.

MARINE CORPS BASE QUANTICO, Va. – If the Marine Corps’ top marksmanship experts get their way, Marines are going to get a rifle retooled with an array of upgrades that will make them deadlier shooters. They recently directed the study of a number of significant changes to the service’s weapons, ammunition, shooting curriculum and ranges and have approved new competitions.

Most eagerly anticipated are recommendations to study overhauling M16A4 rifles and M4 carbines with a host of new features, including a new trigger and barrel, all of which will be a hot topic at the next Combat Marksmanship Symposium in October.

[ … ]

Current M16A4 rifles and M4 carbines could get a significant overhaul with mostly inexpensive components already available to consumers. The upgrades would drastically improve accuracy and function without incurring the expense of procuring an new rifle.

Those updates could include a free-floating barrel, rifle compensators, new reticles for the Rifle Combat Optic, more ambidextrous controls and a new trigger group. With significant advancements in rifle technology for the civilian shooting market over the past two decades, those are all features commonly seen on competition rifles and those carried by elite operators.

[ … ]

Standard-issue M16A4s and M4s use hand guards and rail systems that are directly connected to the barrel. As a result, any force exerted on an accessory like a rifle sling used to achieve greater stability also exerts force on the barrel. That can ever so slightly bend or pull the barrel off center relative to zeroed optics. The movement can translate into big variances over distance. The longer the shot, the further the external pressure exerted on the barrel will throw it.

A free floating barrel is achieved by using a hand guard and rail system that does not contact the barrel at any point. So any force exerted on a sling or other rifle-mounted accessory attached to the rail system does not translate to the barrel which contacts the rifle at only one point – the upper receiver. That ensures the barrel and optics which are also mounted to the upper receiver point in precisely the same direction.

“Free floating barrels have been seen in the competition world since the ’90s,” said Layou. “In combat you are not able to apply the same sling tension every time. You are shooting in different positions at different targets. So it’s not a training solution, it is a material solution needed to reduce barrel flex.”

This is a very odd way of explaining it.  Rifle optics can be set up with the assistance of a bore sight to zero at about 25 yards (which zeros the 5.56 mm at 100 yards too without BDC), even given the small undulations in the barrel.  That’s not really the issue.  The issue has to do with the fact that if it is not a free floated barrel there is a hinge point, or a fixed point beyond which the barrel cantilevers.

This point interferes with the natural frequency of the barrel and thus alters the harmonics of the system.  The vibrations send the projectile off directions other than the direction of the bore (at static conditions) without the vibrations from the explosion.  With an anchor point for the barrel, this smooth sinusoidal wave of vibrations becomes an interrupted mess of multiple competing and non-metered or oddly-patterned waves.  The point is this: barrel anchor points = bad, free floated barrel = good.

As I said before, purchasing something Milspec isn’t always the best option, and in most instances today with the progression of technology since mid-twentieth century, it leads to inferior design and manufacture.

WeaponsMan also has a good article on Making an M4 Run Like A Gazelle.