hi there, i to brought a cheap collimator of ebay, its a used simmons, but may be sharpie could help me with this as didnt have much luck with it.
i lined the cross hairs up with the collimator, but when i took it out to try it, its was shooting very high. I used it at 150 yards.
reading on what people have wrote, should i start at 100 yards?
Simon, you are expecting too much by starting at 150 yards, unless you have a very large target to aim at. Better to start as close as you can, say 50 yards, maybe even as close as 25.
Post #25 explains this well.
Also don't expect the collimator to be precisely calibrated. The little grid inside would have to be positioned very precisely, you can't expect it to be perfect for something that retails for £40.
In mine the zero position is out by about 2 boxes right, 4 boxes high, when tested on a variety of known-zeroed rifles. Its quite consistent, and now that I know this I am confident of getting pretty close. E.g. if I just used it without this correction it would put me about 16" high at 100 yards.
This is why a workman needs to know the imperfections of his tools, not trust them blindly.
When you fit the collimator, try to be consistent and repeatable, e.g. tighten the screw that holds the spigot in the same position and tension each time (or leave it fitted, if not using different calibres). Also rotate the unit so that the grid lines up exactly parallel with the crosshairs each time. If it is twisted even a little you will see errors.
Rest the rifle on e.g. a pair of bench bags, or cut a cradle into a stout cardboard box, to set it up. If you try to do it unsupported it is frustrating, it doesn't take much of a knock for the collimator to twist in the barrel and spoil the reading.
TBH I find mine most use for checking out scope adjustments, and as a confidence check before using the rifle on quarry.
I've discovered various horrors this way. Even one quite good scope where the reticle was slightly twisted. When lined up with the collimator grid, the elevation adjustment also moved the windage slightly, and vice versa. Difficult to discover otherwise, the twist was not visible to the eye.
There are so many other checks you can do, e.g. discover the true magnification when mil dots are correct on 2ndFP scopes, are the turret clicks precisely calibrated or even variable, what are the limits of adjustment range when the turret keeps clicking but the reticle has stopped moving, do I need a 20moa scope rail or is there already sufficient range in the scope, is there interaction between elevation and windage adjusters, is the optical centre in the midrange of adjustment, does the zero shift as the scope is zoomed etc. etc.
There are limitations, the main ones are that the scope needs to be parallaxed at at least 100 yards for the grid to be clearly focussed. Fine for centrefire scopes but air rifle and rimfire scopes can be tricky unless PA adjustable. Also very high scopes 56mm plus or smaller ones on very high mounts may not line up close enough to the centre of the collimator, so the full grid may not be visible.
