Any ranges around run carbine only competitions?

You would be looking for 3 gun or other events.

3 Gun is basically scattered from places and during the year.

Other option would be West Coast Armory in Bellevue (Factoria) as they run a weekly Friday shoot.
http://www.westcoastarmory.com/events/e ... eague.html

Renton Fish and Game Club is having a Black Rifle Match - there's a post on here about it. It's more of a night shoot with transitions.
http://rfgc.org/events/
Dec 17th at 4pm viewtopic.php?f=60&t=69941

Another one is Federal Way Discount Guns on Tuesday.
http://www.federalwaydiscountguns.com/Shooting_Leagues

Just a few off the top of my head. I'm sure more folks will chime in.

Steel Challenge at Renton Fish & Game Club allows pistol caliber carbines.
IDPA & USPSA also have been looking at a PCC category, some of the local matches might allow it now.

Black Rifle League at Renton Fish & Game is only a night shoot this time of year. First run should be somewhat light out, second is dark. Building clearing type of course. Ten rifle targets, 2 rounds each, mandatory mag change. Two pistol targets, 2 rounds each. Timed but emphasis on shot placement and use of cover.
Holster necessary, sling strongly recommended.

http://www.WaGuns.org/viewtopic.php?t=69941

Paul Bunyan and UNSC also, I've been running my 9mm AR at both lately, makes the day much more fun than just watching the kid shoot.

P.B. is $5 per gun and is every 3rd Sunday of the month, 125 rounds minimum
UNSC is $15 flat, up to 4 guns, 4th Saturday of the month, 60 rounds minimum (much more low key and smaller than PB)
Check their websites for more info and calendar schedules

Is it pistol caliber only?

Correct. USPSA, IDPA & Steel Challenge is pistol caliber only.
The only rifle caliber around, that I know of, is the Black Rifle matches (referenced above) or the occasional Three Gun match, which I think Custer is the only one on the west side that puts those on.

West Coast Armory in factoria does a Friday night rifle league. there is some pistol in that league, but mostly rifle. The rifle does not have to be pistol caliber.

Thanks