Zeroing and practice targets
Free printable HFT zeroing targets
These targets contain a representation of a mil-dot reticule that you can use to work out the magnification at which your mil-dots are “true”, simply print one of the targets and put it out at the distance marked on the page, then look at it through your scope, adjust the magnification until the mil-dots on your scope line up exactly with the mil-dots on the page, check the mag at which this happens and there it is. For this to work you MUST make sure that the line at the bottom of the page that is marked 150mm measures exactly that, you may have to adjust print options in Adobe Reader to 100% rather than “fit paper”. Don’t worry if it’s not exactly 150mm, close enough will do fine.
The targets also have various size circles on them that represent the different killzone sizes, use these to work out the pellet drop at the various distances and therefore your holdover aimpoints.