Background of Ejection Angle Testing -AR10 style rifles (308 auto-loaders) have typically failed to eject spent casings reliably to the desired 4:00 direction. The reason behind this across-the-industry is incorrect gas-tuning generally resulting in an over-gassing condition, where there is excess gas used to perform action cycling. In turn, this condition results in exceedingly fast cycling which lends to "short ejecting", an ejection angle between 12:30 & 3:00 (15-150 degrees). Short ejecting gives rise to various failure modes such as bolt-skip, rim-skip, partial battery, and case re-entry. Short ejecting also is the cause of casings that drop straight down next to the firearm rather than slinging out several feet from from the operator. Inconsistent angle of ejection is an indicator or erratic and uncontrolled cyclic speed rates that result primarily from two sources: 1) component tolerances in the gas/action system that can cause friction variances and 2) the gas system's inability to regulate between various bullet weights and ammunition loads. Through several years of testing, F&D has found that, aside from barrel condition and ammunition quality, recoil consistency is the greatest variable effecting gas-rifle accuracy, especially stringing scenarios. Over-gassing increases the likelihood of gas/action component friction deviations, resulting in erratic cyclic times and ejection angles . The FD308 gas/action system jumps ahead of the competition: less recoil is felt by the operator, less muzzle rise, higher ejection reliability, consistent cyclic timing, consistent gas/action component wear, 15-30% less gas usage, higher muzzle velocities, and overall accuracy improvements.
Settings -Gas valve set to "normal" high-efficiency orifice; -Precision adjustment at .190
Results -Average ejection angle: 4:00 (120 degrees) -Muzzle rise: Less than 1/4"
Setup -Camera set at 4:00; -Video is edited only to reduce time; -Non-spliced, uncut, 6-round sequential event; -1 second between shots