More than ever, American troops are customizing their weapons, particularly the M-116/M-14 assault rifles. Even before September 11, 2001, there was widespread adoption of commercial accessories for these infantry weapons. Many of these items have since become standard features of the weapons as issued to the troops. But some items are still non-standard parts bought, and installed, by the troops, using their own money. These include components like trigger units and trigger guards, as well as oversize bolt releases and flash suppressors. All these have to do with individual preferences in trigger pull and, for trigger guards, simply needing more room for gloved fingers, and a general desire to have a more effective weapon in combat. Troops can, in effect, replace every component of their M4 or M16 rifles with different, but compatible, components from commercial suppliers. Most commanders allow the troops to make these mods, subject to agreement of NCOs (who know more about such things.)
One of the oldest, and most popular items is the red dot reflex sight for rifles and machine-guns. This sight, similar to the point-and-shoot viewfinder found in cameras for many years, was first used by the military (U.S. Army Special Forces) in 1970, and also became popular with hunters and paint ball gun users. The red dot sight was more accurate than iron sights, could be used with both eyes open and was generally more effective at typical combat ranges (under a hundred meters). The sight was particularly effective at night, and in the 1970s, that was its big advantage.
Current devices, like the U.S. Marine Corps ACOG (Advanced Combat Optical Gunsight), do not use batteries and provides a red chevron-shaped reticle and bullet drop compensator. For daytime use, a fiber optic system collects available light for brightness and controlled contrast in the scope. At night, the system relies on tritium for illumination. The 4x32 sight allows you to get first round hits at 300 meter, or longer ranges. The sight still allows for better accuracy at closer ranges, with both eyes open. The manufacturer, Trijicon, made the original sights of this type back in the 1970s. SOCOM has long used them, and many marines and soldiers have bought the civilian version of the ACOG with their own money. At a thousand bucks each, ACOG costs more than the rifle its mounted on, but the users consider it well worth the price.
In the last decade, American infantry have used a growing variety of lights, visible and invisible, to control the battlefield at night, and during the day as well. The simplest, and cheapest, light source was the Surefire White Light 6P. This small, $65 item puts out a bright, white light that not only quickly illuminates enemy troops, but also blinds them. This flashlight shaped device was initially attached to the end of a rifle with tape. This flashlight is a police item, as are many items the troops are getting for combat in urban areas. A lighting device for purely military use is also available, as are a growing number of weapon mounted illumination devices.
A more low tech, but equally useful item, is the dust-proof magazine. A big problem with the M-16 type rifle is that the fine sand and dust found in Iraq and Afghanistan can slip past the magazine and into the magazine well, and lead to a malfunction. So commercial firms have come out with several generations of magazines that try to seal the magazine well to keep the talcum powder-like crud out of the rifle. The latest of these is the Advanced Reliability Combat magazine, that includes a soft gasket that creates a dust-proof seal when the magazine is inserted in an M-4, or similar weapon (like the SOCOM SCAR). These magazines cost $30 each (about 70 percent more than a standard magazine.) Magazines of this type are also available with another simple, but life-saving, innovation, a strip of see-through plastic running the length of the magazine, showing how many bullets you have left.
All these devices turn an M-16 or M-4 into a much more lethal weapon, and troops were buying a lot of this stuff with their own money, before the army and marines made most of these items standard issue.