If my rifle has a 20" barrel, I'm confident out to about 21".
Where and how I hunt means that shooting from a rest is a virtual impossibility, so my figures are for off-hand shooting. Also, I don't use magnification on my rifles, and - due to failing eyesight - hunt with red dot sights.
I'm comfortable shooting 150 yds at a standing deer, and about 200 yds at a standing moose. If they are moving, those ranges are drastically reduced. The bulk of my animals have been killed at under 50 yds, and my longest was 213 yds on a standing deer. The last shot is one I wouldn't take again.