Didn't see this post until taking a break from work and making breakfast this morning but because Charlie invited me in, I wanted to pass on a few things before I got back to something that will keep me away until sometime late tomorrow.
1) First, I need to tell all of you that I have a number of friends who work for companies that make these things. And make them for both handguns and long guns and for both military and non-military applications. Other than referencing the military ones for a specific reason below, I will not consider them here. And except for an example or two, I will not say much about the long gun models in this posting either.
2) I mention lasers in some of my lectures and do say positive things about them but I really hammer on the drawbacks at the same time. I will do so here as well. You should also know (and Charlie was not aware of this) but it seems that I will have an article on lasers appearing in a national magazine next year (the draft is completed and approved) where I will make some of these same arguments for they are the same things I have been saying in my classes for years.
3) I started working with lasers (for different reasons) in engineering school in the early 1970's. My first gun-mounted laser was a helium-neon device (glowing glass tube and all) that was fitted into the stock of a Mini-14 sometime in the early-mid 1980's. I found it fascinating but limited then and for all their advancements in the past 25 years, I still find them limited now (for non-military applications).
4) First, none of the reputable manufacturers will ever tell you that they are a replacement for conventional sighting systems. Instead, they are an alternative or a supplement. That's because they don't always work. And I am not implying that they are unreliable; for mechanically (electronically, I guess), the good ones almost always do funtion correctly. But batteries fail and, more commonly, there are times (way too many times) that you just can't see the dot.
Ambient lighting conditions and targeting surfaces greatly affect what one can "see" (and that is if the dot is where it belongs - more on that later) and, generally (and this is changing) the dot is red. Not only is red harder to discern (for a variety of technical reasons) than the green-colored ones finally making their way into the market but just like red front sights and in some cases, red dot sights, many of the male users of such devices (obviously the assumed largest group of such users at the moment) might have color "blindness" (I use the term loosely) in the area of the spectrum where "reds" are concerned.
5) For the average non-practiced shooter (better called a user for they don't really "shoot", they just sorta own the guns and "fire" them once and a while), I don't think that lasers help much at all. At least not in terms of speeding things up or, in some cases, even getting on the target at all.
From day one, we tell people to focus on the front sight and align it along two axis with the slightly-out-of-focus-rear sight as it is (now "they are") brought to bear on the generally-way-out-of-focus target. Now I have some issues with this concept of sighting in general but that's a discussion for another day. So for now, let's just say this is a correct technique and again, let's say we're looking at most "non" or unpracticed shooters. And let's put those shooters in a deadly force situation.
I firmly believe that they (and even many practiced shooters who have never been in such a life-or-death position) will look at the threat and not the front sight. (For the record, I think things are/can be different with practiced shooters but again that's outside the bounds of this discussion.)
In theory, most people will do something similar to what "Al Thompson" and "HankB" are doing when they practice. They look to the threat and then drive the gun to it.
This works for "Al Thompson" and "HankB": people who I assume do practice (or they wouldn't be contributing to this forum) and probably have done so more over the course of their lives than most and certainly more than the average non-practiced shooter who I believe makes up a pretty significant portion of the marketplace for these devices.
That's because in many cases, "Al Thompson" and "HankB" have practiced enough to effectively hit their targets under these same circumstances with guns if they had no sights on them at all. (Something else that is outside the time I have available to me today.)
But the average non-practiced shooter will look to that threat and when he or she drives the gun to it, their lack of successful, repetitive responses to targets on the range will, more likely than not, cause them to not be indexed on the threat as experienced by "Al Thompson" and "HankB" on the range.
Were the non-practiced (average) shooter, using conventional sights (or, better yet, something like one of my current favorites, an oversized big dot front sight) they could correct themselves once they realized their error.
Do to time restraints here today, I will overstate things a bit and say that many times, you cannot do that with a laser. If I am off-target with iron sights (or even some optical sights), I can move them where they belong because I can see them in order to do it. But if my "beam" has missed my adversary and there is no referencing dot for me to see (on them or anything else), I'm lost. And by the time, I wrench things around to hopefully "get" a dot, I've lost any time or any benefit that the sight might have provided.
And that's if I'm not dead by then.
And that's if the ambient light, my eyes, and the threat's garments allow me to see a "dot" in the first place if I can get it there.
Not good and one of the primary drawbacks to this concept.
6) I do agree with Charlie and others that as a teaching and diagnostic tool, lasers have a value. I also fully agree with Irish Cop that for people who cannot use the sights that come on the gun, they have a value. In law enforcing circles, people who use carryable bunkers (shields) with view ports are probably the most obvious group of people who could benefit from them in that regard. If you move into the realm of IR (non-visible light) lasers, there might be a handful of legitimate LE applications for them. But the laws governing them are a hassle and rightfully so (as are rules relating the power output limits for all types, which is something else that somewhat hampers performance). Finally, and I am just beginning to study this in depth, I think that there might (emphasis on "might") be some low light applications where there could (emphasis on "could") be some additional value to laser sighting but it is too early for me to say.
7) I apologize but I don't have time to get into the switching issues. They all have their shortcomings. I also don't have the time to talk about the severely reduced battery life in regard to the current crop of green lasers. Nor the theory of where any of these devices are best fitted to the gun. Looks like you'll have to wait until next year to hear my ramblings on all that as well as far more details about the stuff I was able to get to here before getting back to work this morning.
8 Hope this helps and I hope you can forgive my brevity and not dealing with all of the preceding posts in my usual detail. I do not mean to slight any of those contributors.
9) And not wanting to start a war here and not slighting those who believe such things or have been lucky enough to see a positive outcome in their own lives, I still don't think that anyone can count on (or should even consider) a laser sight alone as a deterrent to evil. Am I either adult enough or experienced enough to know that the sight of a gun can have a controlling effect on a situation or an individual? Yes, I know this happens. But there are too many "people" out there who know when they can be shot and many of them can tell if the person holding the gun has the personal wherewithal to shoot them (legally or not). In the real world, these sights do not rise above that level. They might on TV and they might if you're lucky enough to come across someone not committed to their goal at the time. But I'm afraid that touting them in this way is going to get someone killed and that person will not be the cause of the deadly force threat that actually required the production of the defensive firearm.
10) Finally, and this too will have to be discussed at another time (and in another thread for it is truly a separate topic), is the need to recognize that electronics in firearms and accessories are here to stay and that over time, they will become commonplace. Whether it is the lasers we are talking about here, powered red dots that are already used elsewhere or the scopes of the not too far away future [where (once they get image refresh rates a bit faster) they will basically be video tubes that will allow us to see in the dark and thru fog and haze by internally addressing the part of the spectrum we are concerned with at the time and will magnify things electronically rather than optically], electronic sights will become the de facto approach to positioning the gun on its target. And for all the failed attempts to get the public to embrace electronically fired weapons, there will come a time (I'll probably be long dead by then), when it is simply more cost effective to get rid of all the parts (in the gun and in some cases, within the cartridge) and fire these things in a manner unlike what we are used to today.