I'm looking at getting a new scope. Some that I'm considering have a 'mil dot' set-up. Trouble is I don't know what the mil dot system is exactly. Can someone familiar with it explain it to me? Thanks folks.

More than you ever wanted to know about mil-dot reticles. Gives me a head ache and brings back bad memories of high school trig.
Link and cut-n-paste job below. Thought about plagerising the site, and claiming as my own, but figure everbody here knows what a dummy I really am. It does show that some of that stuff they try to teach you in school has pratical applications!! :p


http://www.seidata.com/~adking/mil_dot_reticle.htm

The mil-dot reticle was designed around the measurement unit of the milliradian. The dots, themselves, were designed with this in mind and the spacing of the dots was also based upon the milliradian. This allows the shooter to calculate the distance to an object of known height or width. Height of the target in yards divided by the height of the target in milliradians multiplied by 1000 equals the distance to the target in yards. For example, take a 6-foot-tall man (2 yards). Let's say that the top of his head lines up with one dot and his feet line up four dots down. So: (2/4)*1000 = 500 yards away. This same technique can be used to estimate lead on a moving target or to compensate for deflection on a windy day. The distance from the center of one dot to the center of the next dot is 1 milliradian. We are told (by the folks at Leupold) that the length of a dot is 1/4 milliradian or 3/4 MOA (Given this much information, one can determine that the distance between dots is 3/4 milliradian.).* I use the term "length" because the mil-dot is not round. It is oblong. The "dots" on the vertical crosshair run oblong in the vertical direction. The dots on the horizontal crosshair run oblong in the horizontal direction (i.e., they are lying on their sides). The width of each dot is an arbitrary distance and is not used for any practical purpose. Like a duplex reticle, the mil-dot reticle is thicker towards the edges and uses thin lines in the middle where the dots are located and the crosshairs cross. The distance between the opposite thick portions is 10 milliradians.
*NOTE: 1/4 milliradian = .9" and 3/4 MOA = .785", so, obviously, a mil-dot cannot be both 1/4 milliradian and 3/4 MOA. I called Premier Reticles (they make Leupold's mil-dot reticles) and got an explanation: the dots on their mil-dot reticles are 1/4 mil. They are not 3/4 MOA. Apparently, they (Leupold?) just figured that more shooters understand MOA than milliradians, so they just gave a figure (in MOA) that was close, but not super precise.

What I always wanted to know about milt-dots is, at what magnification? Is a 6 foot man at 500 yards always going to take up 4 dots at 3x as opposed to 9x? I have never actually used a mil-dot scope before but am curious.

-9r

From what i remember reading about mil-dot it is a full magnification. I remember reading that is why the military mostly went with fixed power scopes.

I purchased the Bausch & Lomb elite 3200 with a fixed 10x magnification mil-dot scope for my ar 15. It does allow you to do the estimating whilst keeping your target in the sights.
Try www.snipershide.com and
www.snipersparadise.com

don't let the name or nature of the sites fool ya... there are alot of knowedgable responsible shooters on the forums that can help you.
http://www.snipersparadise.com/marksmanship/range_est.htm

A book called "The Ultimate Sniper" by Major john Plaster is another very goos source for understanding the mil-dot system: he explains the USMC sighting system vs. the Army's way.

Informative reading.

The vast majority of scopes sold in the US have the recticle placed so it remains the same size at any power level, so the mil-dot aspect remains constant. Some European scopes are set up so the cross-hairs thickness increases with magnification power of variable scopes.

Think the biggest reason for the military to use fixed power scopes is the extra margin of realiability. Less moving parts to break or come out of adjustment

M141A,
Thanks for the links, will check them out later.