What is the most commen Cartridge used for Deer in a T/C Pistol?
From what I have read on this sight 7-30 seems to be TopDog .

I would have to say that I've used a T/C Contender SSK .338JDJ#2 more than about anything else in my safe.

375JDJ here :p

although 7-30 is fairly popular among TC fraternity(not otherwise), it doesn't flip my switch as much as a 30-30Ackley improved or 35rem.
i use my 35rem rimmed most. lookin ahead i plan on working up a 150gr nbt load for the 30-30AI to make it a comparable thumper to the 35. so i can have 2 favorites on deck more often.

I would agree with that, and I do have one in a 12"er. It is the flattest shooting (factory) Contender deer killer available, although there are many wildcats that will outrun it. I like the 375 Winny these days, not as flat but it hits with authority and recoil is not punishing like the JDJ.

In the Encore I'd expect the 7-08 and 308 are neck and neck in popularity, but I don't Encore.

For factory offerings from TC, the 7x30 is tops in my book.
I also have a 30-30AI

I have shot a friends 7-30 waters. It was accurate. I only shot it at 50 yards to try it out. Since then I bought a 7TCU. I liked it so much I bought another for my Dad. Together we have taken 8 deer in 3 years. The only difference I can tell is that the 7-30 waters has more recoil. I was shooting paper out to 200 yards this year before deer season. My 120gn nosler BT dropped about 8 inches sighted in dead on for 50 yards. That's pretty flat shooting out of a 14 inch barrel! I took a large doe last year with it at 185 yards. Dropped her in her tracks!

I think anything in the 7MM(.284") is most popular, the 7-30Waters is a fine deer round out of the Contender, I used it alot till I got my 7 TC/U Barrel, I even took a nice blac bear with the Waters round but I have decided on the .257 JDJ as my deer gun now and it has become a favorite from day one at the range, I'am shooting 87gr Hornady softpoints at 2947FPS from a 14" barrel, and 100gr NBT's at 2459 FPS from the same barrel.

We will see what happens to deer this year with it as this will be the first year hunting with it.

I use the 6.5jdj even though I have the 7-30 and 7 tc/u

The 7-30 Waters is a great round in Contenders. The .44 mag becomes a whole different critter in a TC also. Increased velocity and better accuracy than I get with the same round in revolvers.

As a few have posted, IMHO, the 7-30 is about the best deer "factory" cambering available. Custom Shop wise, I would look at a 30-30 AI. It will outperform the 7-30 hands down.

Assuming you are talking about the Contender, if you are asking about all T/C's, I would look at the 7mm08 or 308. Mild recoil and great all around cartridges for deer.

BUT, my next question is what type of shooting will you be doing? Under 100 yards, I would say go with the 375 Win or 44 Mag! Particularly if you are going to be handgun hunting out of your bow stand or shooting around heavy brush.

I have a Factory 30-30 Contender .
I Deer Hunt in a Area where 100 Yards is MAX due to Brush.
However I Do Periodicly Get to hunt a Area That 200+
is Possible.
I also have a Encore Longun That was bought as a Pistol.
I quese the real Story is I Find Myself Thinking about ADDING
More Barrels To my Collection.
I have Heard This is a AFFLICTION that Happens to Us.(T/C Shooters)