Aimpoint's Micro T1 optic is a red-dot tube sight that can be mounted to a carbine. Photo courtesy of Aimpoint.
When I was on active duty with the military, state-of-the-art optics meant a four-power scope that fit onto the carry handle of your M16. Let me tell you, those were hard to come by. Today nearly every GI has some form of optics on his or her long gun, and the same trend can be seen in law enforcement.
The first and foremost reason people use any form of mounted optics is they provide a fast, accurate sight. Second, be they red dot or truly telescopic, sights have shrunk in size, making them better suited for duty.
Back 20 years ago when I was regularly shooting in U.S.P.S.A. and I.P.S.C. Open Class competitions, red-dot sights were in their infancy and few options were available. Aimpoint was the first and biggest player at the time. These sights were hard on batteries, although they quickly proved themselves able to stand up to the tens of thousands of rounds of competition. The other problem many of the neophyte red dots had was size; some of them were huge and bulky.
Throughout the early '90s shooters used numerous red-dot sights in competition, and the battery life and electronics improved. Now you can run a red-dot sight for 10,000 to 20,000 hours on one battery. These sights also shrank in size and weight.
As these improvements were happening, more red-dot manufacturers were cropping up. This competition increased quality, reduced price, reduced size, and increased the popularity of optics for duty and competition use.
Variable Power Scopes
While red-dot sights are still the dominant optic in the military and in law enforcement, I'm seeing a new trend toward using small variable power scopes. The reason for this is simple: There is a demand for them and red-dot sights do not meet all mission requirements.
As fast and accurate as red dots are, when you start engaging targets at distance or precision is required, a one-power red dot may not be the best choice. Instead, a scope that gives you four- or six-power magnification gives you speed at close quarters and accuracy at distance.
In addition to being flexible and meeting more mission requirements, these scopes are growing in popularity because they now have proven themselves in action with the military. Like red-dot sights before them, small variable power scopes have advanced in technology to the point that they're combat worthy. With reticles for CQB work and with ranging capability, newer scopes meet the mission applications of police and GIs.
Personally, I use both red-dot sights and variable power optics on my M4s, SIG 556, and even my DSA FN FAL. This allows the rifle and scope to meet my needs at any given time.
Mini Red Dots
When it comes to red dots, I like the new "mini" red dots because they are small and lightweight. They are also tough as nails and can be mounted on telescopic rifle scopes should your precision marksman suddenly find himself in a CQB situation.