Originally Posted by alex71168
is there any other way of working that out as I also guessing that the distance you actually require is less than the actual distance between the scope centre and the barrel centre?
Yup, the distance will always be smaller.
I don't know of a more accurate and/or easier method. There's several problems that the tin foil method overcomes - packed mounts, rails that aren't level, barrels that aren't true etc etc.
The tin foil method sounds complicated but it's really simple to do and takes minutes.. the only thing to be careful about is that you have a backstop that isn't going to ricochet when you fire a pellet into it at the muzzle.
If you don't get the hole exactly in the centre and your head central behind the scope there's a chance you'll get some parallax error, but the error will be so small it can be ignored. That's about the only couple of things to watch out for with that method.
Just to explain the method...
- Fix some tin foil over the objective of your scope with a rubber band
- Select the lowest magnification and parallax distance for your scope
- Make a small hole (5mm?) in centre of the tin foil - doesn't have to be exact, but the more central the better.
- Get a bit of card and a draw a cross on it with a marker pen
- Put the card on a safe backstop with no chance of a ricochet
- Touch the muzzle of your loaded gun on the card and when your crosshairs are pointed at the cross pull the trigger
- Measure the distance between the cross and the hole you've just made in the card.
If you can't see the cross, repeat with a smaller hole. You'll also need to do this with plenty of light.