I'm still a bit confused on the type of weapon. An AR-10 uses the same Stoner gas system as an AR-15. The HK 91 uses roller delayed blowback with no gas system.
If the pressure curve of the .308 Winchester is too long, failures to eject and subsequent failures to feed in many semi-auto guns may result. The problem is that a long pressure curve (slowish powder) means that the case walls are still gripping the inside of the chamber when the action is trying to open.
In a FAL this can ultimately lead to the extractor ripping the heads off cases, usually after the owner has adjusted the gas system to send more gas to the piston to cure with anemic ejection. The fix is to reduce the gas to the action, allowing the pressure in the case to drop before attempting extraction. This is totally counter-intuitive to most as ejection will still be anemic, but at least the case head and rim will be intact.
With a roller delayed action, the chances are that too long a pressure curve may result in poor/no extraction/ejection.
The rifle throwing the working empties 15 yards is typical for the HK-91/CETME action. There should be stripes down the length of the cases created by the flutes machined in the chamber to help extraction.
