Type I sights are non-magnified red-dot optics. They are optimized for zero to 100 yards, and are
most effective within the cartridge's point-blank distance, which is about 275 yards for 5.56. On
large targets such as full silhouettes, they can make hits out to about 350 yards, but from 400
yards and further, compensating for over three feet of bullet drop is problematic. Type I optics
are typically reduced-parallax or parallax-free red-dot sights with no magnification. The most
common Type I optics are the Aimpoint M2, M3, or M4, and the EOTech.
Unity magnification red-dot sights are easier to use when on the move than other optic types. Shown
here is an Aimpoint M2.
Unity magnification allows the fastest sight-picture acquisition and the shooter can maintain true
binocular vision while shooting. At extended distances, the lack of magnification is a liability in
target location, identification, and sight picture. Type I optics are appropriate for virtually
all defensive rifle uses, and are the right choice for fighting with 100 yards. They excel at
shooting while moving and shooting from awkward positions like rollover prone, supine, and the
weak-side shoulder. Iron sights still have a place due to their dumb-as-rocks mechanical
simplicity, and fit in as a Type I sighting system, although they do not enjoy many advantages of
the Type I optics.
The Aimpoint M2 (bottom), M3 (top), and M4 models provide battery life of 10,000, 50,000, and
80,000 hours respectively, and can truly be left on "all the time," ready for immediate use.
I'll go out on a limb and call the Aimpoint M3 and M4 the best choices for a fighting Type I optic.
The EOTech has followers and is used in harm's way, however, the Aimpoint line trumps the EOTech
in several important respects: the Aimpoint's battery lasts much, much longer than the EOTech and
the Aimpoint can be turned on and off using only tactile feedback. The shooter needs to be looking
at the EOTech to determine if it's on. Market price for an EOTech or Aimpoint including
quick-release mount ranges from about $500 up to $700.
Without any magnification, the Aimpoint's maximum realistic range for making hits on silhouette-size
targets is about 425 yards, using Kentucky hold-over.
Aimpoint offers a 3x magnifier which can be mounted behind the optic to provide some of the
capabilities of the Type II sighting systems, yet can be quickly flipped away when it is not needed.
Compared to natively-magnified optics, this combination-magnifier has much less field of view.
Type II sights are low-power magnified optics with reticle features providing aiming points for
distant targets. The Type II optic should not have external knobs to prevent loss of zero due to
the knobs being bumped. They are optimized for 75 to about 400 yards. Type II optics are generally either
fixed magnification in the three to four power range, or are variable power in the one to four
range. The most common Type II optic is the Trijicon ACOG, in either the 4x versions (TA31, TA01) or
the 3.5x version (TA11). The US Military realizes these capabilities in the Designated Marksman
Rifle (DMR) and Squad Designated Marksman Rifle (SDM-R).