Few weeks ago I bought a brand new 'Just Right Carbine' chambered in 9mm and fed with Glock mags.
When I first got the carbine I took it home to take a close look. I checked it for function using snap caps. It fed ok, ejected ok and the mil-spec AR trigger group seemed to have a powerful strike. Like all brand new guns that I have bought it was a little dirty where I assume it was test fired at the factory. I ran a Bore Snake thru the barrel few times but that was all I did.

A week later I took it to the range, chambered a round, pulled the trigger and got a good powerful hammer strike but no Bang! I did that a few times, no Bang! Checking the primers there wasn't the slightest indication of a firing pin strike! Those particular rounds fired fine in my XDM.
 The gun store where I bought it is a 5 minute drive from the range so I dropped it off there for them to ship it back to the manufacturer, 'JRC' in Canandaigua, New York so I didn't get to check it out.
I never did do the test where you drop a pencil down the barrel eraser end to breech face to verify there is a fire pin strike.

Any ideas as to what may have happened between factory test fire and when I got it?
Any of you run a JRC in 9mm?
I've read a few reviews on the JRC and all have been good reviews.

Thanks
VonBark

I would have called JRC directly and been connected with their tech dept (IIRC) Tom.  Curious did you check visually to see if the FP was functioning?
Our 9mm's work fine. The 45 conversion needed some tweaking.

I can't remember if my JRC .45 came out of the box clean or dirty, but did a quick search and I don't see any mention of JRC performing a test fire from the factory. Not everyone does that.
If not, and yours was dirty then someone fired it before it came in your hands.
Sounds like you pretty much covered the basics in troubleshooting, other than trying other types of ammo. But if the ammo you used fired in a handgun I'd rule out bad/out of spec ammo.
Only other suggestion I'd make would be to remove the bolt and give it a good cleaning, maybe crud on the firing pin. But too late for that now.
JRC has a good rep for customer service and should make it right.

I bought a 9mm JRC a little over a year(or maybe more)ago. I've never fired it but you can be dang sure it will make it out for my next range session!

Mine worked great when I took it to the range.  The only thing it had trouble with were a couple of Korean made 30 rd Glock mags.  They would wobble a bit when seated and this cause it to not feed right a few times.  The factory Glock 30 rd mags worked fine.
 

You're as bad as I am. Can't even remember the last time I shot