Whether your newest one-hand gun is brand spankin' new or an old workhorse gotten in a swap, chances are its sighted in for someone else's eyes, and ammunition. I'm not one of those of the "Kentucky windage" fraternity. I want my gun to shoot where I aim, and I want to aim where I intend to shoot. Seems to me to be the most intuitive way of shooting.
First of all, lets understand a few laws of the handgun. Recoil affects bullet impact, as does velocity, bullet weight, gun weight, and even the shooter's grip. Recoil, or "kick", occurs simultaneously and in opposite direction to the bullet's flight. The same energy that pushes the bullet out the muzzle, pushes the gun straight backward. The difference in bullet weight to gun weight keeps your recoil force slower than bullet velocity.
Straight back? The recoil impulse is in a straight line opposite to the bullet's path. But, the resistance of the shooter's hand on the grip is in a line lower than the line of the bore, so the opposing forces are offset. The result is a "pivot point" that makes the muzzle jump upward in recoil.
Many years ago, Winchester published a photo of a .30-30 barrel still resting on a block with the high speed camera catching the bullet several inches from the muzzle. The conclusion from this photo is that recoil does not occur until after the bullet exits the muzzle. Not true. Neglected in this evidence was barrel whip, or the flexing of the barrel under recoil. Handgun barrels are shorter and stiffer, so whip is negligible. Examine a handgun with a level across the front and rear sights and it will be noted that the bore is aligned somewhere below the target.
Two factors affect the recoil "arc" of a handgun, bullet weight and muzzle velocity, both of which translate into "barrel time." Barrel time is that period between firing and the bullet's exit from the muzzle. During this split second, the gun is recoiling in its arc. Light bullets, at high velocity, get out quicker, and generate somewhat less recoil. Heavy bullets remain in the bore longer, and generally produce greater recoil.
To summarize so far, light high velocity bullets tend to strike lower. Heavier and slower bullets tend to strike higher. This assuming in the same gun. Further, increasing, or decreasing friction between the shooter's hand and the gun's grip, can and does affect sighting. Someone who sights in with a buckskin glove will find he may be off when shooting bare handed, or with sweaty hands.
So, assuming the shooter has chosen the ammunition he will use most often, now to sight in. It's best to have a paper target set at some distance, I prefer to sight in at twenty-five yards with a six inch diameter bulls-eye. I prefer not to use a rest, as your gun may recoil differently using a rest and without it. I stand, using my two-hand hold, sort of a modified FBI stance or so.
I prefer my guns to be sighted with adjustable sights, and the following applies to iron sights only. Scopes are a different creature altogether.
The rule is to move the REAR SIGHT IN THE DIRECTION of the desired shift in impact. And to move the FRONT SIGHT IN THE OPPOSITE DIRECTION of the desired shift in impact. So, if the first group is at the six o'clock position (low) then the rear sight must be raised, or the front sight must be lowered. If the group is at the nine o'clock position, then the group is to be moved to the right, thus move the rear sight to the right, or the front sight to the left.
When I sight in my guns, say a Ruger Super Blackhawk, I use a 240gr. cast SWC at about 1200 feet per second velocity. I crank my rear sight about mid height in elevation, and hopefully, my groups will be on-line vertically. I fire a five shot group, and if only a click or two is required to hit dead center, everythings O.K. But, sometimes, that's not the case.
If I'm hitting low, considerably low, then out comes the file. I take usually fourteen strokes before firing again. Why fourteen strokes? The first time I tried this I counted fourteen, been doing it ever since. Nothing magic about fourteen, just don't go too far at one time. Fire another group, and continue firing and filing until the group is centered. After sighting in, touch up the filed blade with cold blue.
But now high groups occur. If you've bottomed out the rear sight and still too high, then a taller front sight is required. That happened with the last Super Blackhawk I stumbled across. I ended up taking my gun to Keith Warner, my local gunsmith, and he milled off the blade, slotted the ramp, and installed a higher blade. I had left him a box of my handloads, and he adjusted the blade for these. When I got the gun back, only a slight tweaking was required to get dead center. Keep a proper fitting screwdriver in your shooting kit. And consult your guns manufacturer's instruction sheet for which direction to turn the adjusting screws to move right/left and up/down.
Ah, but what if the wayward handgun has fixed sights? If you're handy with tools, these are fairly easily corrected. As with the adjustable sighted gun, the front sight can be filed to raise bullet impact, but to lower the groups, a taller sight is required, and that is the job for a good 'smith. Sometimes windage adjustments can be made by clamping the gun in a vise, specially set up to grip the barrel without marring, and the barrel turned in the frame to move the front sight left or right. I've done this on occasion, but the adjustment is not too precise, requiring a lot of trial and error. If you don't feel comfortable doing this, head for your gunsmith.
With adjustable sights, and sighted in with my loads, I can make adjustments when shifting to loads of differing performance. But, once sighted in, I usually am reluctant to move my sights, preferring to buy another gun. But, as I said, I prefer to have my gun come up to eye level with the assurance my point of aim and point of impact coincide.