Grizz. The 7-30 is not a rare barrel or a rare caliber. I mean, it's a nice sales tactic, but an even better sales tactic is the fact that the 7-30 is one heck of a good deer caliber.
The 7mm bullets have one of the best, if not the best Ballistic Coefficients of any bullet made. These cartridges are incredibly accurate (I have one in a 14" Contender handgun and it will put three or four in the bullseye on a regular basis!) and will take a whitetail down with one shot out to 250 yards with ease!
With a MV @ 2500fps the bullet will only be about 1.5" high at 100 yards when zeroed at 200 yards. And it will carry about 1400 ft\lbs of energy at 250 yards when it impacts the deer! That's with a 120gr Nosler BT bullet....which is a recommended whitetail bullet for the 7-30.
And reforming 30-30 brass to the 7-30 is a breeze. Just run the 30-30 brass thru the 7-30 sizing die to widen the case mouth, then shoot a low level load to expand the shoulder and push it out to the 7-30 length. Easy.
What is rare about a 7/30 contender barrel? I see them for sale everywhere. There are a bunch of reasons the 7/30 is a great match to the contender that is why they are so common. Where did you hear they were rare?