Re: shooting a gun sideways?
Brian that is true but I believe he may be talking about the issue of mechanical offset. This is obvious, but with a scope mounted two inches or so above the bore then the bullet will, in effect, "rise" up to the line of sight, cross it while continuing to "rise", then come down and cross it going back down. As you pointed out this is not at all due to a bullet somehow generating lift or rising as it travels down range. It's the direction that the bore is pointing that sends it on that intersecting path through the line of sight.
On closer targets you can shoot with some degree of cant without much effect. As you get farther away that becomes more of a problem. If you're shooting a .308 with a 175 SMK at a 1,000 yard target your bullet will be about 10 or 11 feet higher than your line of sight at about the 550 yard mark. Imagine if you were canted to the right. That bullet would not travel in a line straight up and straight back down to the target (let's leave out wind for this). If you're canted then the bullet will travel up at the angle of your cant so it's already going off course, come to it's highest point in the arc, then start dropping out to the side continually drifting away from the target.
Not sure if I explained this well or not I hope it makes sense.
As for Jerry's AR I couldn't tell you what he has but I have seen three gun shooters run small sights on their scopes and they set them at an angle and run them for close range targets. I've never done that so I can't comment on that technique. I would think they zero that sight for that technique and just use it for close engagements. How close I have no idea.
Marc