First of all I don’t own a JM940 model. I do own 2 930 models. Nothing I have seen on the 940 indicates it has a magazine cut off. My 2 930 models do not have one either.
They do have a way to quickly empty the magazine tube without cycling the shot gun over and over. This could work in reverse to what Mossy Man describes. Basically it could work like this. Assume 1 shell is in the chamber, bolt is closed and there are a few in the mag tube and the safety is on and gun is pointed in a safe direction. With one hands fingers lift the shell elevator out of the way. Press the mag release button with the other hand and all the shells will empty out of the mag tube very quickly. Then cycle the action and take the one out of the cylinder. Gun is cleared. This is unwieldy but possible. A mag cut off is much simpler.
My Browning semi auto has a magazine cut off and it does come in handy.
They do have a way to quickly empty the magazine tube without cycling the shot gun over and over. This could work in reverse to what Mossy Man describes. Basically it could work like this. Assume 1 shell is in the chamber, bolt is closed and there are a few in the mag tube and the safety is on and gun is pointed in a safe direction. With one hands fingers lift the shell elevator out of the way. Press the mag release button with the other hand and all the shells will empty out of the mag tube very quickly. Then cycle the action and take the one out of the cylinder. Gun is cleared. This is unwieldy but possible. A mag cut off is much simpler.
My Browning semi auto has a magazine cut off and it does come in handy.