Wednesday, January 5, 2011

Accessories: Lasers, Supressors, and Scopes

...Oh my.  Sorry, had to do it.  OCD thing.

When most people think of gun accessories, three things come to mind.  Scopes, laser sights, and silencers.  The truth is that there are a lot of other things that fit this category, but it’s those three I want to look at in depth.

First off, laser sights.  I touched on these briefly in the Exterior Ballistics section, but I want to go over them again.

Most people know what a laser sight is from TV and movies.  It’s that red dot that creeps along the hero’s face until it stops right between his eyes.  It’s become so ingrained that the bullet will hit that spot no matter what that no one bothers to even question it.

Well, here’s a question.  What is the Zero Distance for that gun?

The Zero Distance is the range where the bullet will intersect with the line of sight.  If I want to be “dead on” at 200 yards, I can sight in at 100 yards and place my bullet 1.1 inches high.  The ballistics for that bullet show that it will then be right on at 200, and roughly 1.8 inches low at 300.  If the target is 600 yards away and I’m aimed at the center of his head, I’m probably going to hit somewhere around his liver.

That’s problem number one with laser sights.  In close range situations, they are accurate enough to be effective.  This includes nearly all ranges for pistols and sub machineguns.  For ranges over 100 yards or so, they are far less reliable, even if the dot could be seen.

That brings up problem number two.  The dot shows up very well for the target because the target is right there.  From 200 yards away, the shooter may not even be able to see the spot, and if they can, there is so little detail on the target that there is no way to be sure where the dot is resting.  Is it on his heart, or his right shoulder?  This is actually easy enough to test now that laser pointers are cheap.  At a range of 100 yards, most laser “dots” have grown to a 1 inch or larger blob of diffuse light.

One Hollywood solution I’ve seen a few times is to use telescopic sight to make the dot show up for the shooter.  This adds a whole new level of silliness.  It’s using a far superior targeting method as a secondary system to one that shouldn’t be used that way in the first place.

Problem three.  The target is now aware that there is a weapon in the area.  Other people in the area may also be aware of it.  The general position of the shooter can be determined because the laser has to have a direct line to the target.  Any hope of having the element of surprise is gone.

So, laser sights on handguns and SMG’s used in close quarters combat, like a house, fine.  That’s a perfectly legitimate use for them.  Laser sights on a sniper rifle, not so fine.  Borders on laughably silly.  For an assault rifle used for clearing houses in an urban area, that’s basically what the close combat one covers.

Telescopic Sights, or Scopes.

These are tubes that increase the apparent size of an object by bending light through lenses.  They have a few parts and terms in common, and we’ll go over those below.

The Objective Lens, is the one in the front.  This is the one you don’t look though.  Generally speaking, the larger this lens, the more light the scope will bring in and the higher the magnification can go.

The Reticle is the thing that is laid over the top of the image.  It’s usually called the cross hairs and in its most basic form, it looks like a plus sign (+) that goes all the way to the edge of the image.  Some scopes will have more elaborate reticles that include range finding scales and windage meters, while others may simply have a small circle in the center.  One thing they actually will have in common is something in the center. Of the field of view.  I’ve seen a few shows where the scope had all sorts of cool stuff in it, but lacked anything that might show where the freaking bullet was going to go.  Seriously, the + shape is fine.

Adjustment Knobs.  These sit on the center of the tube, one on the top and one on one side.  Their purpose is to move the reticle until whatever is in the center lines up with the impact of the bullet.  Once this is set, there is rarely a good reason to move it on normal scopes.  Some high end sniper scopes are made to adjust the knobs from one shot to the next to compensate for range and wind.  Most scopes made for the general public are adjusted using a coin for a screwdriver.

Scope Mounts.  This is what holds the scope on the rifle.  Yes, there are some that can be slipped on and off and maintain their aim point.  Most are simply screwed into the top of the rifle and ignored forever after.  For some scopes, the mounts have the aim adjustments, rather than the scope.  For some sniper scopes, the mounts can be quickly adjusted for range to compensate for bullet drop.
Eye Relief.  This isn’t a physical thing, but an absence of it.  The distance between the shooter’s eye and the part of the scope closest to it is known as the eye relief.  Because of the way lenses work, there is a “sweet spot” where the shooter has to be to see a full picture.  This is true of telescopes, binoculars, and even magnifying glasses to some extent.  If that sweet spot is too close to the scope, when the rifle recoils, the scope will hit the shooter in the face.  This normally results in a crescent shaped cut on the eyebrow or bridge of the nose, and weeks of ridicule from friends that recognize it.

In the section on Sniper Rifles, I talked about magnification.  I don’t want to go over that all again, but I do want to add to it.  As magnification increases, three things happen. 

The image will get darker and lose contrast.  This is why scopes with higher magnification have larger objectives.

The angular size of the objects in the scope get larger.  This also magnifies any shakes or tremors the shooter may experience.  It’s generally considered impossible for a normal person to hold 15 power binoculars steady enough to use.  Those are still easier to manage than a rifle with a 15 power scope on it.  From a rest of some sort, 30 or 40 power is possible, but if the target moves a tiny bit, or the shooter twitches for any reason, the target will end up completely out of the view.

Atmospheric artifacts increase.  The main of these is mirage.  On a hot, or even warm day, moving air currents can refract the light between the target and the scope to the point that the target seems to float away like a helium balloon.  The shooter is still lined up, but can’t tell because the air is distorting things.  Higher magnification makes this more common.

The following will tie in, I swear.

One type of US military sniper scope in use for decades has a cam on the rear that will adjust the height of the rear of the scope to match the range to the target to the ballistic arc of the bullet fired.  If the shooter knows the range is 800 yards, he sets the scope to 800 and aims directly at the target.

Another scope from the Soviet Union (I think) worked in a similar way, but also used the zoom function of the scope as a range finder.  Two lines represented the average human from head to navel  The target was selected, then the zoom on the scope was turned to fit the target between the two lines.  Three power was 300 yards.  Nine power was 900 yards.

Did you catch that?

At 900 yards 9 power was adequate magnification for a military sniper scope.  You don’t need to see their eye color, you just need to know where the center of the head is.

Silencers, or more accurately, suppressors.

These have been mentioned a few places already and this is running long.  That bulky black thing on the end of the gun will not make it silent.  At best it will make it quiet enough that the people in the house next door won’t think it’s a gunshot.

When a bullet is fired, it’s usually going faster than sound.  This creates a sonic boom, but because the bullet is so small, it’s really more of a loud crack, kind of like a whip makes.  The expanding gasses hitting the air make a much louder sound.  A suppressor catches this gas and slows it down in an effort to quiet it.

To be truly effective, the suppressor must be huge.  The ones seen on the barrels of SWAT team weapons are not intended to make the weapons silent, only to take the bite out of the sound and allow for communication with teammates and hostiles in the area.  If their ears are ringing from the gunshots, they can’t very well follow instructions.

Improvised items can be used as silencers for a shot or two.  Classically, a pillow works well, but it spreads feathers.  For a while, there were attachments that allowed the threading of a 2 liter soda bottle to the front of a gun.  This was supposed to work for a few shots before the bottle was too damaged to be effective.  Under the laws at the time, the adaptor was legal, but actually putting a bottle on it was not.

Suppressors can be owned by private citizen in the United States.  They require a lot of paperwork and the permits can be refused for any number of reasons, but in some states it is possible.

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