I posted these in a thread regarding Corbon DPX as part and parcel to my response to Wink in regard to his experience with Corbon having a lower point of aim as relative to that of other ammo he is more familiar with.
The results he experienced are very much expected as per the physics from the multiple changes in the ammunition between that of DPX as compared to more common design and type ammunition of the same caliber.

That thread with my response can found here; Corbon DPX

I am reposting these sources here under their own threads for the purpose of archival toward what is should be known and understood information as in regard to the dynamics of firearms, ammunition, and how the two function and correlate to result in hits downrange.

Adjustable Sights

American Handgunner , Annual, 2000 by Charles E. Petty

Got problems fine-tuning your sights? Here are some on-target tips and tricks.

Adjusting a gun's sights is one of the most common jobs in shooting. On the surface, it seems like an easy task and it is easy-- in a perfect world. But we all know that the world isn't perfect and things rarely work the way it says on the label.

Many shooters have a love/hate relationship with their sights, mostly because they don't understand how the adjustments work. Several years ago, Smith & Wesson customer service received an old Model 25 revolver. The rear sight was jacked up as high as it would go and the blade was to the right as far as possible. The letter accompanying the gun asked Smith & Wesson to please fix the sights. "It still shoots low and left all the time," complained the owner. Sadly, the adjustment needed wasn't of the sights, but of the owner. Jerking the trigger will make any gun shoot low and left for a right-handed shooter (for southpaws it's low and right). No sight adjustment is going to solve that problem.

Metallic Sights

Let's begin by defining some categories. There are two basic types of sights: iron and optical. An iron sight can be steel or plastic. Iron is rarely used in anything these days; actually, "metallic" is the correct term. Metallic sights are either "fixed" or "adjustable," just to complicate things a bit more.

Fixed sights are almost exclusively a handgun feature and, once more, there are some variations. Many revolvers have really fixed sights: The rear sight is a notch in the frame and the front sight is frequently integral to the barrel. These take heroic measures--like bending the barrel or cutting metal--to adjust.

Then there are mostly fixed sights as featured on semi-autos. The front sight is built into the slide but the rear sight can be moved within a dovetail. Purists call these "drift adjustable" sights. Another sub-category is guns with moveable or replaceable front sights. Elevation changes are made by adjusting the height of the front sight, while windage adjustments are made by moving the rear sight.

It's rare for rifles to have completely fixed sights. Most permit some elevation adjustments. These can be made by either loosening a screw, adjusting some sort of ladder arrangement or sliding a part under the rear sight--thus, raising or lower it. Windage adjustment on these types of sights is often made by drifting.

Fixed Sights

With really fixed sights, you're at the mercy of the gun's designers. They decide which bullet weight and velocity to use to regulate the gun and its sights. Many years ago, when there was only one load for a cartridge, this really didn't matter. Today, however, there are many choices. Consider the .38 Special. For generations the "standard" load was a 158 gr. lead, round-nose bullet with a velocity of 760 fps. The height of the front sight was set so the load would shoot to the point of aim. But a significant change in velocity or bullet weight could and did have an effect on elevation.

This "dwell time" relates to the time the bullet spends in the barrel. Even though this time is measured in milliseconds, it affects the elevation, The barrel will rise, due to recoil, before the bullet is completely out of the barrel. So the height of the front sight is established for a "standard" load, based on a bullet that takes "x" milliseconds to exit the barrel. If we increase the velocity of the load--either by reducing the bullet weight or increasing the powder charge--we reduce the amount of time the bullet is in the barrel and the load will shoot low.

Perhaps the best-- and worst-- example is the .38 Special. You can buy ammunition loaded with bullets from 110 to 200 grs. and at velocities between 730 and 1,000 fps. There is no way all of the loads are going to shoot to the same point of impact in a revolver with fixed sights. And there really isn't very much you can do about it except to stay with "standard" loads. If you want to shoot really light, fast bullets, you have to either accept that they're going to shoot low or modify your front sight.

Semi-autos are more forgiving than revolvers when it comes to point of impact shifts, and many of them have front sights that can be replaced. Here's the rule: If the shots are low, you need to lower the front sight; if they're high, you need to raise it.

Adjustable Sights

Most "adjustable" rear sights on handguns are marked to show you which way is up: A counterclockwise movement of the screw is usually going to raise the point of impact. A clockwise movement of the windage screw will usually move the point of impact to the right.

There is always going to be an argument over whether or not you should have adjustable sights on a defensive handgun. Most "experts" who argue against adjustables point to the sight's "fragile" construction. While that may be true mechanically-- unless you drop the gun or use it as a club-- the concern is largely irrelevant. A far more compelling argument is that adjustable sights have more places to snag on clothing or interfere with carrying and drawing the gun. This argument does have merit. It would seem most gun owners have a strong personal preference for fixed sights on defensive guns...

The full article can be found at;
- Janq