The Army did a study titled "
Effects of Rifle Configuration on Quick-Fire Accuracy".
In this test, two weapons of comparable weight and recoil, but differing only in configuration were tested against each other to see which configuration was best for the quick, snap-shot engagement inside 100 meters. The shooting subjects ranged from inexperienced shooters to expert shots. The range had pop-up targets arrayed in a arc of a 30 degrees in front of the shooter and ranging from 20 to 60 meters, the targets were dropped after a set time interval. Instructions were simple, when a target pops up attempt to drop it as fast as possible, and continue to shoot it until in completely disappears from view. The grading criteria were: a) how long did it take to get the first hit on the target (seconds), b) how many total hits were made, and total number of shots fired per engagement.
The weapons were: an M16, an M1 Carbine, and a modified M1 Carbine. The modified carbine had the rear sight removed and a shotgun type rib, with front bead, mounted on the receiver ring and going to where the front sight would be.
Over two weeks of shooting, and all of the subjects got to shoot each configuration several times the results were:
Time to the first shot fired was pretty much the same averaging around 1.1 seconds after target. However, the time to the first hit, and ratio of hits to shots fired where quite different, the modified Carbine had almost twice the hits to fired than the M16 and consistently was faster with the first hit. The regular Carbine was in between the Modified Carbine and the M16.
The conclusion was that a conventional stock, with a simple sighting rib, (a typical shotgun set-up) is the best configuration for rapid engagement of target inside 100 meters.
Range layout:
Modified Carbine