Indoors is definitely situational. I have people living above me, but not below, so for me, down is best indoors. I prefer down outdoors as well, as what goes up…you know the rest of that one. People are hit all the time by rounds fired into the air, and some few are killed that way.
But, as has been noted before, ricochets are a serious issue when the ground is concrete or even just rocky. I’m not convinced there’s any one way that is always correct outdoors. Use that situational awareness and add environmental awareness to it each and every time, then make the choice with the least risk. I’d say if possible, move to soft ground and point down whenever you can. If you must point the barrel up, assess the angle of the weapon, and try to point that angle in the direction least likely to have people nearby. Nearby, when talking about bullets, is a long, long way indeed.
BOTH, the situation is going to dictate high vs low ready. I have small children i tend to train from a high ready however there are situations where the high ready is safer. So train for both and use them appropriately
I have not read any replies yet, so this may already have been brought up, and I am sure there will be plenty of opinions to consider.
Generally, if I hold a firearm muzzle in any direction other than where my eyes are looking, it is down. Yes, ricochets can happen, but it is usually less likely someone will be injured if pointed down… however, depending on the situation and location, I have held it up (I do not prefer this if possible as it could lead to a bullet sailing off into the nether land and reentering from orbit in a random and dangerous location), …
Down would be perhaps safer, if you need to move from the direction your eyes are looking, and depending on situation, location, and who you may be working with, up.
I know that does not give a definitive answer, but … as with many things, it all depends.
Indeed, but I took his question to be involving handguns. Did I misread?
Never mind, just scrolled up and saw it. Missed it where he now asked about rifles.
@Brandon46, far too many hypotheticals. If you want to know.
It depends.
Primarily, always have your firearm aimed or pointed in the direction your eyes are looking, but if you must move the muzzle to a safe direction, down would generally be the preferred… for most cases, as it depends on the situation, and environment and location… up can be good, for some situations but, what goes up (in case of a discharge) will eventually reenter from orbit.
I would ask, why the concern? Practice both, plan and consider both, and then consider situations where one or the other would be the better choice.
Yes. This.
I think always down unless you’re in a boat 
Just be safe!! Situations very.
I learned every bullet has to land someplace. Pointed at the ground you know where that is. As brought up earlier, concrete surface in a crowd, would make a difference. Keep in mind, a bullet does not ricochet as you might expect. It will usually hit a flat surface then follow closely along the surface of what it hit, even if hit at a 45 degree angle. It dosent bounce like a ping pong ball. Keep your environment in mind.
Simplest explanation:
Always keep your firearm pointed in a safe direction
… however I prefer
Always keep your firearm pointed in a the SAFEST direction because in most situations there is no safe direction at all…
This safety rule was made for a purpose…
Being at home the safest direction is the ground.
Other story if we look at this from tactical perspective…
Good question: I give you my take on this. If your firearm discharged while you had it pointing up where would that round go? If you had it pointed down where would that round go? Which way would the round travel further? Remember what goes up must come down. A downward discharge may cause a ricochet, but the round may not travel as far due to fragmenting. In my opinion I would rather have it pointed down.
Just to add to what I previously posted it does also depend on the environment that you are in. Are there a lot of people around, you have to consider that.
Always pointed down.
If the long gun is pointed up it can block and impair your view of a potential threat.
If pointed up, with a startle reflex you will pull the rifle down in a defensive type posture without regard for what maybe in front of you. If already down, you WON’T pull it up, thus inadvertently flagging the wrong person.
Raising the rifle UP ONTO target in more efficient than dropping the rifle down trying to FIND the target.
There is more arm fatigue by holding your firearm up for extended periods of time.
You should already have trained with a handgun to keep your firearm pointed down in a High Compressed Ready position and then driving it out on target, this is more inline with your muscle memory of coming on target quicker and more efficiently.
And, remember “straight out” means you already have a threat acquired, so again, keeping the long gun at the low ready position is safest until a threat is identified.
The classic dueling stance is down at a 45 degree angle
When a target presents it self you can raise the pistol to fill the sights.
Pointing upwards you restrict your field of vision, especially when lowering the pistol to fill the sights,
At least that’s what we were taught back in the Pony Express days
I’ve heard “back in the pony express days” a hand full of times and finally decided to to Google it.
Those were some brave men.
You should hold your muzzle away from anything you dont intend to kill or destroy, while at the same time your finger should not be on the trigger unless you are on target and you know what will ultimatly stop your bullet.
If the direction the muzzle will be pointed is north, south, up, or down will be dictated by the situations unique circumstances (and if you are on a boat)
I was trying to find safe direction on the boat… 
@Jerzees this should also be in the MEME thread. 
No firearms in the submarine please!
Ground, for the most obvious of reasons. If a accidental discharge happens, what goes up must come down. Gravity has this effect on flying objects without wings. It was pointing at the ground when a little discharge happens, obviously it goes into the ground. 
That was supposed to be “accidental discharge”