If time and ammo is that short leave what is on it now and start shooting at distance. If you can't afford to experiment you can't afford to change either.
That.
If I can't experiment & feel confident at X yds I shorten my self-imposed limit to one I can be confident at.
I wouldn't care to mount a CDS scope on a rifle unless I could test accuracy on-range.
Good luck w/ the hunt. I have no doubt you'll do well w/ a 300 yd limit.
