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4570,
I like to shoot a right and then a left, check for impact points and let the rifle cool just a little, then shoot another right/left combo and quit for awhile. Let your rifle completely cool between four shot groups. Your first and second shots need to be your best ones when hunting so I feel it is best to regulate and then sight in with a cold gun. That's the way it will be when hunting.
Getting ahold of a chonograph is excellent advice, you should buy one if you don't already have one. You can learn alot from a chronograph if you pay attention to what it is telling you. I would be more concerned with the fact that the one barrel is shooting that much higher than the other one. Are the barrels soldered together on your gun? If so, you can correct the vertical spread by heating and adjusting. My guess is though, that your gun may have been poorly regulated to start with. To begin with, you should not be shooting over 50 yards, 25 is better to start with.
Try different loads till you find one that shoots equally well in each barrel. You do that by shooting right barrel groups and then left barrel groups. You are trying to find the load that shoots the tightest groups in both barrels combined. Then adjust the barrels till they shoot to the same POI. Shooting at 100 yards to begin with leaves too much room for personal error. You are not out to prove what a good shot you are at 100 yards, but rather trying to learn what your gun is doing.
I know too that this goes against all the "conventional wisdom", but when regulating, I do most of the work sitting down at a bench so that I get maximum stability. Your 9.3 isn't going to kick you much anyway, and you will get a more accurate idea of what the gun is really doing. Place some items on your bench table till it elevates your forehand enough that you can shoot sitting straight up as much as possible. That will allow your body to soak up recoil clear down to your waist. Be sure that you are holding the guns forend the way you do when shooting offhand and only use the padded support to hold your forarm steady, that way it can feely recoil just as it would when hunting. Never let either of the barrels get hot to the touch while shooting, the hottest barrel is going to try and expand from the heat, and it will. You never know which way it will move the POI of the barrels but they will move. It seems that the more intense the cartridge is, the harder it is to get the gun regulated. Big bores with heavy slow moving bullets are easy by comparison Good luck with it. Bob H.