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I'm using an old BSA century (club rifle) for indoor 25m standing and prone shooting ... I'm unable to change the size of the front aperture because the required elements are AWOL .. However the rear is adjustable ... I've only ever picked up the rifle and used it in the past without considering this adjustment .
Im thinking that the smallest aperture i can get away with the better to increase accuracy ?
Could someone with experience help out ??

zzr1100 wrote:I'm using an old BSA century (club rifle) for indoor 25m standing and prone shooting ... I'm unable to change the size of the front aperture because the required elements are AWOL .. However the rear is adjustable ... I've only ever picked up the rifle and used it in the past without considering this adjustment .
Im thinking that the smallest aperture i can get away with the better to increase accuracy ?
Could someone with experience help out ??

Unlike foresights, generally a smaller aperture is better than a bigger one; however too small and you'll get a rubbish sight picture. Try the following and let us know how you get on:

1) Wind the aperture open as wide as it will go
2) Looking through the rearsight, wind the aperture smaller and smaller until the sight picture starts to get too dark or you start getting "threads" in the sight picture (distortion from diffraction)
3) Open the aperture up a tiny amount until the distortion goes away

I use from 0.7mm in very bright conditions up to about 0.9mm if it's very dark, but I have the rearsight very close indeed to my glasses when I shoot and I shoot pretty much exclusively outdoors. As with foresight apertures this can be quite individual.

Good luck!

Gaz

Hi Gaz,
thanks for the advice, ill give that a go on Friday evening and let you know ,.,,
Regards
Boyd

Will the zero change when the aperture size changes ?

zzr1100 wrote:Will the zero change when the aperture size changes ?

Assuming your rearsight iris is on straight, then it probably shouldn't change very much. Why do you ask?

Gaz

Just curious ... It's an old rifle and probably an old sight ... I need all the help I can get !!!

zzr1100 wrote:Just curious ... It's an old rifle and probably an old sight ... I need all the help I can get !!!

Ah, OK. Good luck!

Gaz

zzr1100 wrote:Just curious ... It's an old rifle and probably an old sight ... I need all the help I can get !!!

The standard size that was on old Anschutz non adjustable rear irises, was 1.1 - I have a relatively long eye, even with .22, so find that too small...but as Gaz says; regardless of your eye relief, as it's adjustable then tweak it until it's the smallest you can get it without it going grey...

The other thing I find that helps on .22 rear sights is a rubber cup that pushes onto the sight, shielding it from direct light.

Thanks for your help folks ... Got the aperture just how I wanted ... Scores didnt improve coz i was having a "wobbly" night but the targets were much much clearer !!