I've been told that at least in some brands, the mil dots in the reticle are only valid for a given range at one power setting. Is this true for all the common brands of rifle scopes?

Mil-Dot scopes are only valid at a given power setting unless they are a first/front focal type scope.....$$$$. They can be used at any range if you know the size of the target.

You forgot caliber & bullet weight!

What does caliber and bullet weight have to do with a mil dot scope? The function of a mildot scope is for simple range estimation, then you can calculate holdover/turret/windage adjustment for the caliber/weight bullet you are shooting. If you stick to one load its pretty simple but if you have several loads/calibers you can get real confused real quick.

the mil has nothing to do with caliber or bullet weight. a mil is a measure of angle like MOA. either mil or MOA can be used to extrapolate the range to a target if the size of the target is known and the hash marks or dots on the reticle are known.

but the front focal plane scopes can be used to range at any power, but second focal plane scopes will only be accurate at one power setting.

if you know your ballistics for your rifle and cartridge, you can make a chart that allows you to use the dots for hold overs or windage holds also.

the mil system is very useful but takes a little effort to master. this day of laser range finders takes some of the effort out of ranging, but the dots are still useful.

sorry bsn, you posted the same stuff at the same time...