Monday, April 07, 2008 Rama: Dio's opus By Karlon N. Rama Stage Five
I BROUGHT a friend to Mario Abangan’s U-Mar’s Gunshop a few days ago and, while my friend and the old gun guru talked about getting a gun fixed, Juhnards, Mario's younger son, handed me a manuscript he said I might find interesting.
Given the nondescript title “M-16 Rifle Weapon System” the book-bound document was prepared by a Cebuano mechanical engineer – Mr. Sansin Dio.
Dio’s research on the platform, said Juhnards, has been extensive. And it has spun off into a business – the manufacture of specialized springs for any M16/AR15 variant.
He begins with a brief history of the weapon, starting with Eugene Stoner’s AR 10 design in 7.62 mm, followed by the scaling down of the prototype to fire the smaller .223 cal. round, and thus giving birth to the AR15 sometime in 1958.
He also discussed the production history of the gun, from the workshop of the ArmaLite Division of the Fairchild Engine and Airplane Corp., to the corridors of Colt’s Manufacturing in Connecticut where the AR15 was adopted for military use and designated as the M16.
He cited the difference between the original M16, which first came out in 1965 and is identified by the noticeable absence of a forward assist and a menacing three-pronged flash-hider; the M16A1, which came out in 1967 and now features a forward assist and an “all-new bird cage” flash hider.
He also discussed the M16A2, with its easy adjustable sights, heavier barrel, faster twist but limited bursts-of-three full auto capability, the M16A3, with its removable carrying-handle, and the shorter and more maneuverable the Colt M4 (three round bursts on full auto) and M4A1 (full auto capability) carbines.
He also summarized the gun’s debut in the Vietnam conflict, how the gun earned the undeserved bad reputation of being unreliable because the army neglected to follow specifications while making the cartridges they issued the gun with.
The army didn't use the specified DuPont IMR gun powder. Instead, they used gunpowder for the 7.62 mm cartridge. The latter left more residue when burned, causing the gun to gunk up, with soldiers not knowing why and how to fix it.
Let me lift from some of the text.
“The heart of the AR15 is the direct gas system, developed by Eugene Stoner in the early 1950s. This system uses no conventional gas piston and rod to propel the bolt group back after each shot is fired.”
Instead, after a shot is fired, residual hot powder gases in the barrel get directed to a stainless tube and get pumped back into the receiver to cause the bolt carrier to move back against an initially stationary bolt.
“As soon as the bolt is rotated to unlock from the barrel, the bolt group continues its rearward travel under inertia. The residual pressure in the barrel (extracts) the spent case, (and compresses) the buffer return spring located in the butt stock.
“On forward movement, the bolt group first strips a fresh cartridge from the magazine and, on the final statement of the movement, rotates the bolt to lock into the barrel extension.”
When this is completed, the gun is ready to fire again. But to fire the next round, the gun must first be placed into battery.
“The first round is brought into the chamber by pulling the charging handle (after the magazine is inserted into its proper place) and releasing it. By doing this, the bolt, the part that moves within the ejection port, is pulled back beyond the magazine slot. As the bolt slides back, it catches a round from the magazine and slides it up a ramp and into the barrel.”
And on why the gun remains appreciated 50 years after the prototype came out, Engr. Dio writes: “The M16, often called the Black Rifle, earned its popularity through its successful performance in a multitude of military environments.”
