The magazine looks like a regular 9mm type, however, there should be a spacer welded in place inside the magazine for the .380 round. The lips on the top of the magazine casing are also different than the 9mm magazines. We did test fire an R380 early on using a 9mm magazine for kicks to see if it would work, and it did work, mostly, but there were some occasional jams with it.
So, in closing: You can sort of shoot the R380 using a 9mm mag, but is will not be as reliable as using the correct 380 magazine.
Eric R.