With no gas you won't be able to unlock the gun easily. You might have to put the butt on the ground and use your heel - not a good way to treat your gun. You need a bit of gas for primary unlocking.
I imagine any damage to the bolt occurs at peak pressure. This is when the bullet is 2.5" down the barrel and at the 0.3msec mark. The gun is still in battery, so turning the gas off won't make any difference to the peak pressure.
I imagine any damage to the bolt occurs at peak pressure. This is when the bullet is 2.5" down the barrel and at the 0.3msec mark. The gun is still in battery, so turning the gas off won't make any difference to the peak pressure.