If you haven't bought your 158g ammo yet, keep in mind that higher velocity (+P) ammunition tends to shoot lower than standard velocity for the same reason that lighter bullets tend to shoot lower - less bullet time in the barrel and hence less time for the barrel to rise before the bullet leaves the muzzle.

BTW, if you take virtually ANY revolver and lay a straight edge from the top of the rear sight to the top of the front sight, you will see that the barrel points "down", below the line of sight, because the engineers KNOW that the muzzle will rise while the bullet is traveling down the barrel. (Same is true of pistols, but it's usually harder to see the line of the barrel compared to the line of the sights.)

The trick with handguns, especially those with fixed sights, is to find a grip strength, bullet weight and bullet velocity combination that let the muzzle rise just the right amount when YOU shoot it so that the bullet hits the point of aim at your intended distance. Adjustable sight guns give you some leeway, but even they can run out of adjustability if grip strength is badly out of whack or if the distance becomes too great.

Good luck at the range tomorrow.