January 04, 2011
I could not believe my eyes. The instructor had just drawn his pistol and presented it on its side as part of a classroom exercise. His offending technique wasn't repeated on the firing line, so at the time I simply dismissed it as another Hollywood affectation creeping its way into life.
When fired from on its side using iron sights, the Kimber .45 ACP pistol put its shots about 21/2 inches low and to the left at 25 yards. Though technically "misses" compared to when the Kimber was shot upright, they weren't far off.
Seeing him do that got me thinking about the dynamics of firing a pistol from on its side as opposed to upright. The real world does not always conveniently lend itself to a nice isosceles or Weaver stance, and there could be times when an unorthodox stance is necessary. Scenarios came to mind: cops having to shoot from under their cruisers while lying on their sides; homeowners firing from under the bed. It occurred to me that if there was a significant change in point of impact from shooting a gun on its side that it might be better to simply save your ammunition for a better shooting position.
One of the things I considered about shooting a gun from this position is that bullets are normally launched upward and are pulled down by gravity into the target. Gravity pulls down and not to the left or right, so it stands to reason that if fired from a gun on its side, the bullet would continuously diverge from the point of aim to the left or right relative to the target and depending on the attitude of the gun, and at some distance that deviation might be enough to matter. Also, since there is no upward firing of the bullet with the gun on its side, the impact should be low, equal to the bullet drop at a given distance.
Another thing I considered is that handguns are actually pointed slightly downward when sights are aligned on a target. Recoil causes a handgun to rotate upward, and the bullet doesn't leave the muzzle until after some degree of muzzle rise. So would firing the gun on its side alter the gun rotation from recoil? And if so, would it alter it sufficiently for that to make a difference in point of impact?
To make things even worse, I considered the effects of sight height and that all of the ballistic modeling I have seen takes sight height as a positive value relative to the bore line (meaning that the sights are on top of the barrel), but that most laser sights are mounted below the bore line. I know from experimenting with positive sight height values that it does make a big difference in a bullet's path (not drop) to the target. Sights mounted higher to the bore have a lower, or flatter, midrange trajectory, so while firing a gun on its side when using iron sights might cause a miss at a given distance, would using a laser sight result in a more or less severe miss at the same distance? Then I thought about how when using a laser you're not really aligning the gun by using the laser but by its dot projected on the target.
Compared to using iron sights, using a laser sight didn't seem to make a significant difference in bullet point of impact when the gun was fired from on its side. It did, however, make aiming considerably easier.
Trying to consider all of the factors and their possible influences got so perplexing that I decided I needed to have some actual observations to work with. I consulted Oehler Research to find out if its Ballistic Explorer software could accurately interpret a negative sight height value. It turns out that newer versions can, and the programs were written that way because of--you guessed it--laser sights.
I plugged in a mild .38 Special target load zeroed at 25 yards, reasoning it would have the most exaggerated trajectory, and used a +0.5-inch sight value for iron sights and a -1.0-inch sight value for the laser. The results showed that when using the laser sight, the bullet's trajectory peaked only slightly above the bore (about 0.2 inch) compared to when iron sights were used (about 0.75 inch). Since there was less a need to launch the bullet upward when using the laser (because the bullet was already starting above the line of sight), it suggested less bullet divergence when fired from a gun on its side than for a gun with iron sights.
For range testing, I devised two scenarios, both fired at 25 yards and both using a center hold on a Champion VisiShot 100-Yard Sight-in target. Its eight-inch black bullseye is easy to see and align handgun sights on, and the orange reveal from bullet hits is clearly visible from the shooting bench.
Low-velocity .38 Special 148-grain wadcutter target loads showed the greatest difference in point of impact between firing the revolver upright or on its side. This suggests that high-velocity, flat-shooting loads fired from a handgun on its side will miss by a smaller margin.
Not everyone uses a laser sight, so my first scenario used an iron-sighted Kimber Stainless Gold Match in .45 ACP with Magtech 230-grain FMJ ammunition fired from a Ransom Rest. Once the gun was settled in the rest and the iron sights aligned to the point of impact, I posted a fresh target and fired eight rounds from a full KimPro Tac-Mag into the center of the target. I then rotated the Ransom Rest's base 45 degrees, adjusted it so the sights were again aligned on the center of the target, and fired another magazine full.
The second scenario used the identical gun and ammunition but with a Crimson Trace Lasergrip. Because the Lasergrip is not compatible with the Ransom Rest, I used a Caldwell Tackdriver rest to help hold the gun perfectly still for each shot. With the gun held upright, I aligned the laser on the center of the target and fired a full magazine. I then held the pistol on its side, realigned the laser dot on the center of the target, and fired another full magazine.
A couple of things were apparent immediately. First, if I wanted to determine with a high level of confidence how much difference existed between firing the gun upright and on its side, and between iron sights and laser sights, I was going to have to fire a lot more groups. I would have to determine an acceptable confidence level and sample size, then fire that number of groups with the gun held each way and with the two different sighting methods. But because I set out to show only that there was a difference and not how much of a difference, I opted
against the exhaustive firing.
Second, it was obvious that a gun fired from on its side has its shots impact in a different area of the target than from a gun fired upright. With the gun on its left side, shots hit noticeably low and left. If held on its right side, shots hit noticeably low and right. I had expected the amount the bullets hit low to be equal to the -1.58-inch bullet drop at 25 yards, but in this instance it turned out to be roughly twice the computed drop.
Finally, the difference in point of impact between sight types for the two holds appears modest at best. The results were so close that I had to plug all of the shot coordinates into a multishot analyzing program written and given to me by the late Dennis L. Marshall to find the group centers for comparison. From the limited amount of shooting, it appears that using iron sights with the gun on its side will put your shots closer to the point of aim than when using a laser. The trade-off, of course, is that with an unorthodox hold or stance, you can aim more accurately with the laser. So it's probably a wash as to which is better.
I repeated the laser experiment using a Smith & Wesson Model 640-1 revolver with .38 Special 148-grain wadcutters. The shots from the gun held on its side hit about a half-foot low and left, which suggests that with flatter shooting loads you'll miss by a smaller margin.
For general defensive purposes and when firing flat-shooting loads at typical defensive distances, there doesn't appear to be a significant point of impact disadvantage to firing a gun from on its side. If a long or precision shot is necessary, however, the chances of it being a good shot are greatly reduced. If you're shooting in a competition where you have to shoot your gun from on its side, and the score really counts, compensate your aim a little if it's a long shot, but take the shot knowing you have the advantage of knowing that the point of impact will be different.