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.
The reason for the M27’s lackluster bolt life has to do with its gas system.
In detail, the HK416’s operating rod transmits the kinetic energy of the expanding gases to movement in the moving parts group virtually after gas is tapped into the gas block, rather than allowing the gas to expand via a tube as in Stoner direct impingement.
This means that if gas is not aggressively vented early (such as via the uncorking of the bullet from a short 10.5″ barrel), then the system is subjected to considerable excess thrust from the high pressure gases still acting on the piston as the bullet travels down the remainder of the barrel’s length.
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.
A more sound approach would be to leverage the competitive environment to procure something better, lighter, and cheaper.
One area where a new rifle might improve over the M27 is in the bolt and gas system configuration.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.To explore this idea further, I sat down with an anonymous small arms subject matter expert to discuss the M27 IAR, its potential as an infantry weapon, and other possibilities for the next Marine Corps infantry weapon.Together, we came to a surprising conclusion: The M27 IAR is not the right infantry rifle for the Marine Corps.Since then, the HK416 has greeted the wider market largely as a carbine-length-barreled true assault rifle, but it has always retained the original gas system design of the short barreled variant.