This article is an excerpt from the Gun Digest Book of Classic Combat Rifles.
Among the changes from the AR-10 to the AR-15 were revised sights to accommodate the flatter-shooting 22-caliber cartridge; elevation to be adjusted via a threaded front post sight rather than within the rear sight, where a less expensive L-shaped peep sight was substituted. The resulting rifle was 37½ inches long and weighed an incredible 6 pounds empty; 6.12 pounds with a loaded 25-round magazine.
The AR-15 made use of high-impact fibrite stocks, pistol grips and handguards. A selector lever on the left side of the rifle could be manipulated with the shooter’s right thumb without removing the hand from the pistol grip. The magazine release, on the right side of the receiver, could be operated with the trigger finger; when pressed, the magazine would drop free.
A fresh magazine, requiring no camming — or ‘rocking’ — could be inserted straight into the magazine well. This attribute contributed significantly to speedy reloading in combat situations compared to its closest rival, the AK47/AKM. These are two of the main reasons why the AR-15/M16-series rifles are considered the finest human-engineered assault rifles in the world.
A bolt catch mechanism is located on the left side of the rifle. When the last round was fired, the magazine follower would elevate the bolt catch and lock the bolt to the rear. After inserting a full magazine, the rifleman would push in on the upper portion of the bolt catch to release the bolt and load the rifle. The receivers, produced from 7075 T6 aircraft aluminum, which helps keep the rifle lightweight and dissipates heat better than conventional metals, are hard-anodized with a non-reflective matte gray weather-resistant finish.
Stoner went to Aberdeen Proving Ground for ammunition assistance. He enlisted the expertise of Robert Hutton, known as the father of the 5.56×45mm round. The pressures involved were more than the 222 Remington case could handle, so the 222 Special was developed.
Sierra Bullet Co. made the 55-grain full metal jacket boat-tail bullet and the first “222 Special” ammunition was loaded by Remington Arms. This cartridge, with a muzzle velocity of 3250 fps and a maximum effective range of 460 meters, became the 5.56×45mm Ball M193/223 Remington.
Tests by the Infantry Board and School at Fort Benning went very well for the AR-15. Stoner personally delivered the weapons and conducted training and familiarization classes for all involved in the testing. In March of 1958, the Board found some “bugs” in the AR-15 system. Some of the resultant changes incorporated in the first rifles were reduction of the trigger pull to seven pounds; replacement of the one-piece handguard with a two-piece triangular handguard; magazine capacity reduced from 25 to 20 rounds and the switching of the selector lever settings.
The Board found the AR-15 to be nearly three times more reliable than the M14 in the development stages. Despite the positive conclusion of the test, Dr. Carten’s report stated the AR-15 had not demonstrated sufficient technical merit and should not be developed by the Army. Accordingly, the Ordnance Corps lost interest in the AR-15.
When Bill Davis, at the time Chief of the Small Arms Branch at Aberdeen Proving Ground, first encountered the AR-15, he was quite impressed and found it had no shortcomings that would not be worked out in the normal course of development. Davis thought Carten’s decision to drop the AR-15 rifle was a bad one and that the weapon held great promise.