asking a lot
A deer at 200+ - 300yds is asking too much from the x39 cartridge. Trying that will leave you disappointed. Heck, a deer at 300 is a long poke w/ any rifle!
I've got a Mini-30 and find it a useful carbine, and hunt deer w/ it a bit every season. You are right when making a comparison between 30-30 and the x39, at least on whitetails. I consider mine a woods rifle, and typically hunt it in locations where shots do not present much at over 100. I've killed my biggest whitetail ever w/ the x39 ctg, and bamaboy a few more as well. None have been over 75 yds and many half that. Through and through wounds on all, and all but one fell on the spot. The big'un went about 50 yds w/ no heart.
In addition to running out of steam at the distances you mention, and looping trajectory much past 200, there will likely be an accuracy issue as well. Most Mini-30's do about 2-3 MOA. That's pretty loose accuracy past 200, when you factor in drop, wind, wobbles, game movement, etc
Mine just got a Leu 1-4x scope, and zeroed 1" high at 100, I figure any deer this side of 150 is in trouble.