Most Whitetail deer are taken at 40 yards or less in the Eastern U.S. Are you suggesting that a .30 Carbine is not capable of enough accuracy at that distance?
Under 40 yards does not require much accuracy, so yes the .30 carbine is quite capable at that range, as is even a recurve bow. But @ 40 yards or less, there are a myriad of other options out there that would perform better terminally and are just as , if not more, accurate.......including the old Indiana standby........ a slug-gun.
The biggest reason so many in Indiana are jumping on the new handgun caliber cartridges now legal for use for deer is because outta a rifle/carbine you theoretically can extend the range over what you could do with a standard smoothbore and they are theoretically more accurate at longer distances. There is a substantial cost savings on ammo also if you don't reload for shotgun. For a 40 yard and under deer gun, I see no realistic advantage of a .30 carbine over a slug gun, or any other handgun caliber cartridge long-gun. It would simply be a "I got one, so I'm gonna use it!" . I don't have a problem with that. As I said, if it's legal any opinions on use are of ethics, and the .30 carbine is legal. Arguing ethics on the internet is like kicking yourself.
I did find out tho that FMJ is illegal in Indiana so there shouldn't even be a discussion on that. IME, out to 125 yards, a rifled barreled slug gun, using sabots is a very accurate platform, and still a better option than a .30 carbine. Others may have dissimilar experiences and are free to disagree. Kinda what we do here.
My experience with .30 carbine accuracy comes from buying a Mil-Surp from a barrel from Montgonery-Ward back in the 60s when they sold for $99. The only other experience I had was with a friends Ruger Blackhawk revolver. Neither had what I would call "match grade" accuracy. It could have very well have been the use of Mil-Surp ammo in my carbine, but from talking with others with them, accuracy was not the priority. The fun factor of shooting a lot of ammo fast and inexpensively was. I found references for accurizing my carbine and tried many things that only slightly improved the accuracy. Others may have had other experiences and the new modern production guns are more than likely, better at the range. Similar to the old Ruger Mini's.