Every thing that Stimpy said is true. Let me expand a little. When you shorten the distance between the rear sight and the front sight, you have to be careful about having the front sight grow too large for the rear sight groove. What I mean to say that the ideal front sight will have the slightest sliver of light on both sides of the front blade when looking at it through the rear notch. That way you can center the blade in the rear sight "slot". If you move it up too close then you will lose that little sliver on each side. It also depends on the type of sight being used. a bead/post sight on the front and a U on the receiver end is a little different. You want the bead to center in the bottom of the U. Again if the distance is cut down then the bead will grow too much to find the center of the U. A blade type front sight can be fixed by slimming it down so that you can still see the sliver of light on both sides or id it is dove tailed in then replace it with a slimmer one. Another way - open the rear notch just a little. With a bead type, the U would have to be opened a little or if the bead is dove tailed in a base, you can change the post/bead size. To be able to tell you what size to get a head of time would be difficult. If there is not drastic changes made, you may not need to change any thing. Some sights have too large of a rear groove to start with. If you have a globe type of front sight with peeps then just changing the peep opening or the front insert will fix it. While we are talking irons, some people think they need to center the front post on the target. I have found, as has many others, that it works best if the target sets on top of the front post. Center the post. align the post with the top of the rear sight and then have the target setting on top of the front sight. You get a much better sight picture this way. When hunting, set the target area on top of the front post and let 'er rip. It is quicker and usually more accurate. Works better for snap shots too. It comes natural after a little practice.