Aperture size question

[taylorkh]

A couple of years ago I "discovered" clear plastic apertures for my front globe sights (Lyman 93). I don't use these for competition, just informal shooting. I prefer a globe site for the shade and better sight picture. I have a set of apertures ranging from 2.4 - 4.2 mm. What I am looking for would be some rules of thumb on how to select the correct size for a given situation. I realize that trial and error is probably the best answer but I am trying to factor out a little of the error. Here is a sample situation:

I have an AR platform rifle with a 20" barrel. The rear sight is a standard A2 sight base with an Armalite hooded sight assembly. I have a choice of .042, .046, .051 or .055 apertures. I currently have the smallest, the .042" installed.

I mounted a Lyman 93 on a space gun mount from Champions Choice http://www.champchoice.com/store/Main.aspx?p=ItemDetailOptions&item=CCAR1050. The mount is attached to a flash hider which has been turned down to .750" diameter and secured with high temperature Loctite. This gives me a sight radius of 26" as opposed to 20" to the standard front sight base.

I will be sighting a target with a 5 3/4" bull at 100 yards. Given these parameters is there any sort of formula to determine the starting point for front sight aperture diameter?

TIA,

Ken

 

[308warbird]

Aperture size is one of the most personalized decisions made on a rifle. No two eyes will see the same sight picture with a given setting. A normal rule of thumb is to pick a front iris setting that is twice as big as the aiming black. Then experiment with tighter and looser lines of white around the black. Choose the setting that produces the tightest group.

There simply is no formula or rule to follow. My shooting buddy uses an iris setting very large, mine is 3.0 smaller at 1000yards, and we shoot very similar scores. Ask 100 people, get 98 different sight settings. Light conditions also dictate what looks right sometimes.

Just experiment looking for the best groups.

 

[taylorkh]

Thanks 308warbird.

I have a good selection of apertures so I will have to do some blasting and see what work best for me.

Ken

 

[nwflycaster]

Taylorkh, as 308warbird said everybody is different and sees things differently. I'm more of the exception than the rule as I prefer just enough white to tell where the black ends. I have much smaller groups when shooting this way, but again most people prefer much more white.

If you have the extra funds I think it's money well spent to get an adjustable front iris. You can adjust it to whatever you like for whatever the light conditions may be easily without even having to unsling.

 

[Immike]

I was having eye strain shooting everything too tight, I learned to trust my eye to naturally center and my scores improved. A lot!

 

[taylorkh]

Thanks folks. I have seen the adjustable apertures advertised. I have not yet gotten that fancy. I guess I need to approach this somewhat scientifically - same lot of ammo, large front aperture, small front aperture, record group sizes, repeat with a different rear aperture size etc.

I have a cataract in my shooting eye which causes some aberrations when using a peep sight. Sort of looks like the rear aperture is dirty. I imagine this will limit the ultimate accuracy which I achieve but I will have fun trying.

Ken

 

[highmaster82]

double the size usually works best and is a good starting point, for the fuzz in your rear sight have the cataract removed and get an implant .that's what I did .I will be 76 in oct and shoot irons about as good as a scope.