With a 6.5 Grendel I doubt it as long as you get an adjustable gas block. Ive never seen a gas port size for a 10.5 6.5 Grendel but the 6.5 Grendel 52,000 PSI maximum pressure might help compared to 5.56. I checked and PSA 10.5 5.56 barrels use carbine length gas and it might be less of an issue than a 10.5 5.56 barrel with pistol port. I saw where Precision firearms sold 10.5 6.5 Grendel barrels but I dont know if Mark used pistol or carbine gas system.
Looking at PSA web site they sell a 7.5 5.56 upper with pistol length gas system. I guess if you ran into dwell time issues with this barrel you might be able to shorten the length. Not ideal either way but sounds like the gas port has already been drilled.
Looking at PSA web site they sell a 7.5 5.56 upper with pistol length gas system. I guess if you ran into dwell time issues with this barrel you might be able to shorten the length. Not ideal either way but sounds like the gas port has already been drilled.