I ran across a video on youtube a couple of days back that showed someone threading the muzzle of a .22LR barrel on a 7 inch lathe, might have been the same one.  He left the action installed.  Never did show whether the threads were concentric, but he dialed in with a 4 jaw chuck and a rod, including running the test indicator along the length of the rod.  The outboard end had a spider he made.

Even an inch spindle bore is cutting things close for barrels through the head stock.

I don't like the limited number of feed speeds (this lathe has one according to the specs!), lack of a power cross feed, and the need to use change gears for every thread or feed change on these little lathes.  I would also down load the manual to check the thread pitches the machine will cut.

Ditto, being for cambering and even receiver work, you really need a lathe with a spindle bore of 1-1/2" at least; and still need a spider on the out board side as well.

As for travel, somewhere in the 30"+ range, since if your tying to get between centers for profiling, your going to need that much for a 29" barrel.

Here you go,
http://www.grizzly.com/products/12-x-36-Gunsmithing-Lathe-with-Stand/G4003G?utm_campaign=zPage&utm_source=grizzly.com

Here's the video I mentioned above:



Jump to about 9:00 to see an illustration of a feature that would get quickly aggravating about this type lathe, where the longitudinal feed is done by hand instead of using the power feed due the gears set up for the previous threading operation.  We could argue that this is good practice for slow and steady hand feeding, plus spring cuts will clean up the final diameter before threading.