Hopefully ya'll think the only dumb question is the one not asked, so here goes. With the G2 on a 14" barrel will those calibers I've put down reach out to 100-150 yards or more with some degree of accuracy. Also will they be enough to take down something like an elk or moose, basically large North American game. Also how about .375 jdj with a 14" barrel? Thanks for all your help, hopefully this wasn't too dumb of a question. As you can guess KYODE, I'm still trying to make up my mind on which T/C to get.

i'm not experienced with the first three calibers, but just going off ballistics, and my experience with elk, I would not use any of the first three you listed. I myself purchased a 375jdj for elk, with the 260 grain bullet I'm using it should be a 200yd elk gun. honestly I have not yet shot an elk with a pistol but the 30-30 is extremely marginal past a 100 yds for deer with a rifle. I live in the middle of elk country, where we have roosevelt, rocky mtn and cascade roosevelt(mix breed) and I've only met a handfull of people that even use anything smaller than a 7mm rem if they are hunting where the shot has the potential of being more than a hundred yards. i'm sure some of the other guys know of other contender calibers that would work but I would not want to hit an elk with anything less than 1000-1500ftlbs of energy at the animal, not to say elk hav'nt been taken with 243's but thats unethical and illegal in oregon.

You might get by with the 30-30 @ 100 yds with everything being just right, but that's all you'd be doing, is getting by. To be honest with you in a Contender I'd rather use a hot loaded .44 mag with 320 cast bullets than a 30-30 @ 100 yds.
If you're looking for a gun that will do the bigger critters, I'd start in about the .358 JDJ area & go up from there. I'd consider the .35 Remington in a pinch.
The .375 JDJ is hard to beat, & the 45/70 will do the job too.
I have a 14" .444 Marlin barrel(rechambered .44 mag barrel) that I carry when I want a Contender instead of a revolver for moose & it's the gun I'll probably use if I get the chance at a brown bear up here.
With it I'm getting an honest 2100 fps out of a 270 gr Speer God Dot without using max loads(although they are close), & the gun is accurate. I'd have no qualms about moose at 200 yds with it. Still has 1,000 ft pounds of energy at 250 yds. Zeroed at 150 yds, it's 2.39 high @ 100 yds, , -5.9 @ 200 yds, & - 10.4 @ 225. As you can see, after 200 yds it starts falling like a rock, but at that range it's still doing better than a .44 mag will at the muzzle. Out to that range it's performance is at least as good as the .375 JDJ, without any need to neck down cases(I know it's no big deal, but loading straight walled cases is SOOOOO easy!), & factory ammo is probably easier to find. Factory 300 gr loads averaged 1874 fps.
The .44 mag loads I was shooting out of it before I rechambered it were running 1545 fps with a 320 gr cast bullet. I think that will put plenty of hurt on a moose out to 125 yds with no problem, but that is a max load.
I guess the short version is in my opinion there are a lot of better choices than the ones you mentioned for large game.

those 3 calibers will give amazing accuracy at 100-150 yards. especially if you handload something the barrel likes. the limiting factor is more likely to be yourself as to how accurate you can get.
none of "the 3" would be something i'd consider for elk. unless it was really close range with the 30-30 using heavy bullets.
the 375jdj should handle that easily but may take a lil gettin used to the recoil. don't wanna create a flinch er nuthin.

with the right bullet, and a lot of practice the .223, 7-30, and 30-30 in handguns will work well much past 100 yards on varmints and whitetail size game.

if you reload your own ammunition, the 30-30Ackley Improved is a nice contender round. "midway usa" has recently had these on sale for around $191. heck of a deal. love my 14" barrel in this caliber.

a 22lr match barrel sure makes a nice barrel for cheap shooting with amazing accuracy and getting in a lot of needed practice also. might wanna consider that.