I've got a basic full size 9mm P320.  Every time I look at it I think Sig shipping the full size with the carry grip mode would make far more sense.  Both full and compact slides work with the carry grip module and the M17 already is configured that way.

Is there any rail mounted device that requires the full size grip module's rail length or can the carry grip module do it all too?

I guess I just don't understand why they developed both modules.

The carry can mount everything.

The main reason behind full sized rails on most modern striker pistols, is to keep the pistol in battery when the slide is pressed into a target.

This may sound a bit morbid, but this is what a full length dust cover prevents.  If a threat has hold of you, up close and personal, and you have your slide pressed into the threat, if the slide moves rearward enough, the fire control will fall out of battery, and the pistol will not fire.  The dust cover being the same length as the slide, minimizes that chance of this happening.  

This is actually something I test all my duty pistols to make sure they function in the event I have the slide pressed hard into a target.  

We also train for this, being aware of your slide and possible out of battery situations in the event of fighting with a threat and having to use deadly force at this range, "contact shooting".  

1911's don't exhibit this behavior as easily since they have a hammer.  Striker pistols aren't as forgiving, and if the slide is out of battery even slightly, it can disengage the fire control.  

The M17 will not fire if you push the slide into an object moving the slide out of battery.  The M18 isn't as susceptible since it has a full length dust cover.  

Just some food for thought.  Most folks will never have to worry about this type of situation, but as an LE we take this into account, and Soldiers in the military should as well.  



TXPO

Or if you put an X300u on it, then you don't have to worry about it.