.22LR rifle iron sights height difference

[Mizar]

Hello,

I'm in the process of installing iron sights on a rimfire rifle that does not have any, so I can't take measurements. I will use a Brno 1 50/75/100m adjustable rear sight, but will be milling from a billet the front one (probably). Since I don't have much experience with .22LR, could you please suggest what the estimated height difference between front and rear sights should be in order to put me on the target at 50/75 yards? The sight radius will be 16.2".

 

[Col. Harrumph]

I can't give you a full answer but you might find this site useful (scroll to the bottom):
http://www.marblearms.com/rear-sights.html

 

[Mizar]

Thank you, Harrumph, but that chart is valid for centerfire rifles where you aim for sights parallel to the bore. .22LR will hit low with that set up as there is no significant recoil to compensate it. Therefore I need to start with lower front sight, the question is how much (approximate)? If someone could measure their Marlin, or Ruger 10/22, or CZ 455 (or any other rifle they have) sights height and barrel thickness at those points, with the zeroing distance mentioned I can calculate it from there. With some safety margin of course, but really would prefer to file down 0.04" rather than 0.20" from the front sight when sighting in at the range.

 

[Blue68f100]

I would recommend digging up the ballistic table for the ammo your going to shoot, and allow for the velocity to be different. 22LR ammo has quite a spread in velocity. Once you have those numbers you can calculate what will be needed from a Zero bore alignment. I shoot regularly around 80 yrds with my ATD, gun is sighted in for 25yrds/53yrds. I use the old Kentucky windage for this distance, besides I'm shooting down hill at around 8 deg.

It does not hurt to start off with a taller front sight, may be the preferred way since your wanting to set it up for longer than normal distance.

 

[Bwana John]

I would use similar triangles, where bullet drop over range equals difference in sight height over sight radius.

If x = difference in sight height then,

16.5"/100yds(36"/yd) = x / 16.2"

So x = (16.5 "/ 3600") (16.2")

X=.074"

So, the difference in height between the top of front sight to bore axis and the top of rear sight to bore axis with a 100 yd zero is that the front sight is .074" shorter.

The 50 yd and 75 yd blades " should" then zero correctly.

You may wish to look up the drop at 100 for the ammo you wish to use, i got the number for 16.5" at 100 yd with SV ammo from a quick look at a ballistic chart.