This is a section taken from an excellent thread on the B-ARFCOm retro AR15 forum with a lot of really good info on early AR10s, AR15s and some other stuff done by user, Americansheepdog. Link to thread will be at bottom.
According to the Infantry Board report found here (and below), this rifle was tested by the Infantry Board at Fort Benning, Georgia in the summer (July-ish) of 1958. First, it was subjected to a semiautomatic fire test, where it fired 276 rounds with 16.7% malfunctions per 100 rounds fired. It was then subjected to an automatic fire test, where it fired 210 rounds with 24.3% malfunctions per 100 rounds fired. Underwent an adverse condition test, where it was submerged in muddy water. 144 rounds were fired with 32 stoppages. The weapon was fired while being exposed to artificially generated sand and dust. It fired 10 rounds with 10 malfunctions. It was fired while subjected to artificial rain. 100 rounds were fired with 2 stoppages. Underwent hot weather testing and was exposed to 125 degrees F for 72 hours. 100 rounds were fired with 2 stoppages. After this test, the trigger housing was cracked after a total of 2,898 rounds had been fired.
The Infantry Board noted the following deficiencies and suggested modifications:
Major Deficiencies (those needing correction to be suitable for Army use):
1) Trigger housing is too weak and cracks or breaks after approximately 2,800 rounds. Correct by strengthening trigger housing or by removing the breakage force.
2) Projectiles disintegrate when fired into sand, reducing penetration. Correct by thickening projectile jacket or providing steel cored projectile.
3) Rifle-ammunition combination produces flash, which reveals the position of the firer in combat. Correct by providing an integral flash suppressor.
4) Sights cannot be adjusted for windage or elevation, preventing the weapon from being properly zeroed.
Minor Deficiencies (those the correction or elimination of which will increase the efficiency or desirability of the weapon):
1) The safety is awkward to handle. They claim the safety is poorly located and requires considerable force to operate when dirty.
2) The safety is not inaudible, which reveals the position of the firer in combat.
3) The safety projects too far from the weapon and catches on brush, wire, etc.
4) The weapon cannot be put on safe when the bolt is open, creating a safety hazard.
5) The weapon cannot be loaded or unloaded when on safe, creating a safety hazard.
6) The rocker drops out of the weapon during disassembly, making it easy to lose. Correct by making rocker an integral part of the receiver.
7) Rocker can be improperly positioned, causing the weapon to fire automatically on semi-automatic setting. Correct by making rocker an integral part of the receiver.
8) Gas cylinder is not strong enough, causing it to crack.
9) Trigger produces excessive trigger slap when firing automatic fire, producing firer fatigue.
10) Requires special lubricant (Molykote), creating an additional item in the supply chain.
11) Trigger sticks to the rear when particles of dirt, dust, etc., get into trigger mechanism.
12) Magazine spring is not strong enough, causing failures to feed.
13) Weapon fires semi-automatically on automatic setting when trigger mechanism gets dirty.
14) Weapon exhibits undue sensitivity to sand and dust, failing to function properly.
15) Projectiles deflect considerably when fired through brush, reducing hit probability.
16) Rifle-ammunition combination produces smoke, revealing the position of the firer in combat.
17) Rifle is not sufficiently accurate in automatic fire role when fired from the prone position. Fails to meet requirement imposed by military characteristics.
18) Rifle and magazine follower too susceptible to rust, shortening the life of the weapon and follower.
I have not found any mention of number 5 in the Aberdeen test report. Nonetheless, below are Aberdeen’s recommendations regarding the Winchester Lightweight Military Rifle:
From Aberdeen testing, it was recommended:
1) The mechanism be redesigned to improve the function and endurance.
2) The automatic fire feature be eliminated.
3) The barrel be redesigned to give a higher level of safety when fired under adverse conditions and improved accuracy.
4) The rear sight be replaced with one which permits elevation and windage adjustments.
Report can be found here:
Report of Project Nr 2787, Evaluation of Small Caliber High Velocity Rifles – Winchester