I've shot a CX4 with a three lug H&K style adapter on it. It's very quiet suppressed with 147 grn ammo.

The innovations going on in "plastic guns" such as the UMP are finding their way back into Title I guns. The CX4 is very reliable even though the bolt (which looks a lot like a slide) rides on plastic rails. The trigger is plastic, the hammer and sear are plastic. The gun is so lightweight it's ridiculous. The plastic they use is some sort of self lubricating compound that doesn't heat up and wear like you would expect.

The CX4 is an extremely reconfigurable ergonomic gun that can be customized more than you would expect. There are various rail options for mounting lights and lasers - one rail can even be retracted into the housing when not in use. There are foregrips that can fold up when not in use, bipods, and even shim inserts to modify the length of pull. The 9mm CX4 will take Beretta 92 pistol mags including the Mecgar hi caps. You can put the cocking handle on the right or left side - independent of your choice of right or left ejection. Ditto for the drop-free mag release. Being right eye dominant, I prefer RH ejection, RH mag release and to put the cocking handle on the left side. The bolt release is on the left and is not switchable.

Here is a link to a site that shows you how to disassemble the gun and trigger pack. I found it useful when I switched mag release from LH to RH.
http://www.tacticalexcellence.com/stormdissass.html

Here's the trigger pack from the patent office:
http://www.pat2pdf.org/patents/pat6769208.pdf