KP944DC caliber change ?

I've got an older swinging link KP944DC .40 and I have picked up a P94 9mm swinging link barrel and magazines through a trade where I received a big box of gun parts.
Does anyone know if I can switch the KP944 to 9mm simply by swapping the barrel and mags, or do I need additional parts.
Thanks

You have to change the complete upper. The 40 barrel is a larger diameter and the guide rod assembly is different too.

Buckeye is correct. You need to get a complete upper assy to make the switch. It is very easy to do, and gives you another gun to shoot with just a simple change. I know it works fine because I have the same setup. Just had to get the mags and I was good to go.