Doing more reading up on the big-bore end of the T/C spectrum. 45-70 is clearly popular, but Mike Bellm has a great article explaining that .444 Marlin is the optimal T/C big-bore for a number of reasons, and also that wildcats (7mm and up) for the T/C are largely best when based on the .444 brass, as the JDJ series and a number of the Bellm series. .444 apparently has some back-thrust advantage given its smaller head, allowing higher pressures than would be advisable in 45-70. Interesting stuff:
http://www.bellmtcs.com/FAQ/Why.htm
Bellm makes the great point too that since .444 brass is so big, you can take pretty much any existing T/C barrel and rechamber it for a .444-based wildcat, and end up with a nice clean and expertly-made chamber and throat for your .30, .35, .375 or whatnot bore.
That aside, I still have this yearning for something larger that .44/45 in a T/C, but the only folks I see making .480 Ruger barrels are doing them for the Encore instead. I thought this was a bit over-cautious at first, but looking at the numbers a warmish .480 Ruger load is approaching max advisable pressure for a T/C, so I could see makers not wanting to do that even if you pinky-swear to not load hotter rounds (also too the next guy you sell it to might not being paying attention to the caveat).
I
dimly recalled there's a .47/.48 cartridge designed to be the largest round safely usable in a Colt Peacemaker. Basically it's a .45 Colt with a heeled bullet bringing the diameter up to .47, a sort of re-creation of the first variant of the .476 Eley (later variants were apparently actually .45 despite the name, which I'd guess means they really rattled down the bore of the earlier guns). However it involves custom molds and a willingness to do all your own casting, and the slight extra hassles involved in loading heeled bullets. Plus the designers themselves admitted it has no practical use other than just being a fun exercise.
I was close to giving up on having a .48 barrel for a T/C Contender, but then ran across vague mention of the .475 Cooper. As I understand it, it pre-dates the .480 Ruger, and was a cut-down .475 Libebaugh that was even shorter than the modern .480 Ruger is. These days you could make it by just trimming .480 brass down a bit. No idea if there's load data for it, or if someone (smarter than I) could eyeball the .480 load data and say how much it needs to be dialed down for the smaller cartridge. But I figure that one might be worth a look. If it's just a shorter .480, can a guy with a .475 barrel blank and a reamer just ream slightly shorter with a Ruger or Linebaugh reamer? That way you'd have a barrel that no nitwit could unthinkingly shove .480 Ruger rounds into, and I would assume would run at a slightly lower pressure which might push it down into the safe zone for the Contender. Thoughts?