11-22-2019, 11:26 AM
Using QuickLoad and an arbitrary charge of IMR 8028 behind a 123 hr Nosler, the pressure at 12" (simulating a RLGB) is ~13KPSI. By adding 2" the pressure at the point that you tap off the gas ts reduced to ~11KPSI. The pressure pulse decays over the next 0.56 ms in the case of the shorter gas tube (0.49ms for the longer) to ~5KPSI. This translates into a higher volume of gas at higher pressure impinging on the bolt resulting in a more violent bolt motion.
A 20" barrel using a standard rifle length system will see the higher pressure for a substantially shorter period (0,35 ms) allowing the pressure pulse to dissipate as the bolt begins it's rearward motion.
The 2" longer gas system would help by reducing the initial pressure and reducing the duration of the pulse. An AGB (think orfice) would aid in reducing the amount of gas through the gas tube, but you will be dealing with a system that is more difficult to tune over a range of bullet weights and velocities.
A 20" barrel using a standard rifle length system will see the higher pressure for a substantially shorter period (0,35 ms) allowing the pressure pulse to dissipate as the bolt begins it's rearward motion.
The 2" longer gas system would help by reducing the initial pressure and reducing the duration of the pulse. An AGB (think orfice) would aid in reducing the amount of gas through the gas tube, but you will be dealing with a system that is more difficult to tune over a range of bullet weights and velocities.