https://www.thefirearmblog.com/blog/2017/05/07/m27-iar-not-right-rifle-marine-corps/Why the M27 IAR Is NOT the Right Rifle for the Marine Corps
Before we talk about why the M27 would not be the right choice, though, let us acknowledge what it is that the M27 brings to the table as a fighting weapon. To start, versus the M4 Carbine and M16A4 Rifle, the M27 IAR has a superior barrel and handguard system. The M4 Carbine’s barrel is made of the same 4150 steel (a low grade chome-molybdenium steel) that has been the military standard since World War II. In the M4, this steel is button rifled, heat treated to between 277 and 331 Brinell (approximately 28-36 Rockwell C) and then chrome-lined. With the M27, in contrast, the barrel is made of high chromium content Aubert & Duval chrome-molybdenum-vanadium steel, cold hammer forged to give a tapered bore, and heat treated to 41 Rockwell C, then chrome lined. These material characteristics, especially the heat treat, give the barrel exceptional life and accuracy, and it is easily this factor which is most attractive about the M27. In addition, instead of the M16A4’s and M4’s classic delta-ring system, the M27 uses a greatly improved barrel nut and handguard system that interfaces via a groove with a free-floated handguard unit, improving barrel harmonics. For the Marine Corps, the ability to make accurate hits from any position – whether shot slung, from a barricade, off a bipod or pack, etc – without substantial POI shift thanks to a free-floated barrel unit is value-added for each rifleman.
Together, these features mean, simply: The M27 is more accurate, stays accurate longer, and has a longer barrel life than either the M4 Carbine or the M16A4 Rifle. A rifle that maintains its accuracy and precision longer is one that gives more hits, better suppression through closer misses, and overall greater combat effect.
Given then that the M27 offers an improvement over the existing weapons, why shouldn’t the Marine Corps adopt it? The reason at its heart lies in the fact that the M27 is still very much a weapon that was developed in the early 2000s, and selected based on a 2007 RFI. It is not that the M27 is a poor weapon, but rather that, in the ten years since the Infantry Automatic Rifle program was made public, substantial commercial off the shelf (COTS) improvements have been introduced that could provide a weapon of equal or greater capability to the M27, but at lower cost and lower weight. Even better, by upgrading the M4 Carbine various engineering shortcomings inherent to the M27 can be avoided entirely. This sort of improvement could be achieved via a depot level or upper receiver group upgrade program to the existing M4, which opens a number of procurement avenues for the Marine Corps that otherwise would be closed if the M27 were sought instead. Sole-sourcing the M27 as a standard infantry weapon virtually constitutes doing it backwards: Instead of learning from the Corps’ experience with the IAR and implementing the best possible fleet solution to provide the required capability to the Infantry, they would simply be sticking a ring on their first major crush. The M27 does pave the way forward, but it itself is already dated technology. A more sound approach would be to leverage the competitive environment to procure something better, lighter, and cheaper.
