What's the device on M-16/M-4s?

It can be just about anything. Scope, laser rangefinder, aimpoint, NVG device???
The M-4 's carrying handle is removable, which allows for different attachments.

Hope this helps

Its an aimpoint, they are sometimes issued for CQB missions or Squad leaders, etc.

the boxs on the front above the handgard are Lasers, the carry handle comes of the M4A1 so you can plase scopes or red dots on the rail
check out http://www.specwargear.com/ and http://www.militaryphotos.net/ for good photos of the M4s in action and close ups of the lasers

The sighting devices on the weapons are PAQ-4's. They put out a IR beam that you can see through NVG's at night but is invisible to the naked eye. After it is zeroed to the weapon you put the dot on the target and you should hit. They also have M-68 REFLEX sights. These are the scope looking things that replace the normal iron sights. They have a little red dot that you put on the target. Its not a lazer and doesn't put out any type of beam. Again once zeroed to the weapon its really hard to miss your target. The only down side is that you always have to make sure the batteries are fresh before a mission.
We have both in our scout platoon and use them all the time.
Take care,
Pat

My thanks to you all. I recently saw footage of the device in action via night vision television and suspected that the beam I saw projected was IR. Thanks again to all for the info and links.
Paul

the paq-4's are the old thing, now there is something else, it's smaller and more efficiant. can't recall the non. of it cept it starts with a T... then four other letters in the acranym. I'll ask my inf. buddy

All sighting devices are accurate only at the range at which they were zeroed. The big advantages of these sighting devices is rapid target acqusition and FOV. Red-dot ("Aimpoint" type) laser, ghost-ring and "holo-sight" devices can be used with both eyes open Iron sights or scopes require one eye closed whigh can cause problems especially with handguns, I am RIGHT-handed but LEFT eye dominant which means I hold the weapon right handed but instinctivly try to sight like a lefty.

the thing my buddy was telling me about can only be seen with NVG's, and not the naked unaided eye.