k-
I make no claim whatsoever as to be an expert on the T/C Contender. However, I have been collecting barrels since I purchased my 1st one (A super 14") in 1981. In all those years, (And collecting about 70 odd barrels) I have learned a few things.
1st and Foremost: It didn't take me long to learn that I didn't like 14" barrels! Too muzzle heavy!
2ndly: After shooting a bit in a 10" barrel in .223 Rem, I found out that it has waaay to much blast. (I went back to a 14")
3rdly: Any barrel that has a fair amount of recoil to it, I prefer the 12" with muzzle tamer. Especially the .35 Rem, .44 Mag., .30-30, et.al (Basically, I'd grab any 12" barrel that I can find.)
The Contender frame is limited to cartridges of about 37,000 PSI. Thus ruling out the .22/250 and .220 Swift. Either of which would not make any significant gain over the .223 with barrels of less than 14". And also would have horrendous muzzle blast. If you want those cartridges, go with the Encore, at the expense of a bigger and heavier gun.
If you are considering a .45 ACP rifle, I would suggest that you peruse the loading manuals for the Marlin rifle. You will likely find that the 18" Marlin gains precious little over the 5" barreled 1911. (So little in fact that I concluded: Why bother?)
And another thing, most folks that buy the Contender and several barrels soon find out that it's much easier to have more than one frame...
In fact, I have four. And I'd buy another if I were to start buying carbine barrels... (Which I don't intend to...)
My entire collection of barrels are all factory. Altho, I do have some fairly rare ones...
In Conclusion: Bear in mind that the above is merely my opinion. YMMV! In other words... You may want to pee on the electric fence for yourself!
GH