You could try a pipe wrench on it, I'm guessing it would work but would likely trash the nut...but, you could always buy a new nut for ten bucks.
I'd be happy to loan you mine as you requested, but I think that by the time you just pay postage both ways you may as well buy it. I too looked at renting one here:
But heck, when you can buy it for $25 ( a few bucks less if you have dealer pricing)- and it comes with two wrenches; one for the smooth barrel nut as well- it just made more sense to buy it IMO. I'm sure I'll use it again someday.
The Wheeler wrench also has the hole for a torque wrench for installing the new barrel.