Front post vs rear notch size?

[toddinjax]

My 60 year old eyes would love to have a "1 2 1" sight picture because now I have too slim gaps of light on either side of my front post. I currently am not using the widest (4mm) post in my possession as it allows barely any light. I have 2 of the exact same rear sight blades and my machinist brother is going to widen the gaps for me. I have searched several other threads looking for the correct ration to achieve a better sight picture but have found only graphic illustrations of beautiful sight pictures. Can somebody tell me for a 4mm wide front post, just what size gap should be in the rear blade to get something approaching a 1 2 1 sight picture? If it matters the sight radius my a 46m is 36.4m

[Rover]

You're making this too difficult. Just take a flat Swiss file and take some off the sides of your rear sight.

This has been a frequent problem for me, so I use a 3/16" chain saw file (cheap at the hardware store) to hog out the rear sight into a half moon. I actually prefer this method AND rear notch. It worked great for many years for the Russians while they were kicking U.S. butt in world competition.

[dulcmr-man]

I've been told that the front sight and the black bullseye should appear to be the same width when you take aim. If that width post (whatever it is) gives you too little light on each side of the rear sight notch, widen the rear sight. My Morini 162ei has an adjustment for this. If your gun does not then, as Rover said, start filing.

Dennis, aka Dulcmrman

[porkchop]

"I've been told that the front sight and the black bullseye should appear to be the same width when you take aim. If that width post (whatever it is) gives you too little light on each side of the rear sight notch, widen the rear sight. My Morini 162ei has an adjustment for this. If your gun does not then, as Rover said, start filing."

Dennis, aka Dulcmrman
Dennis, you have an idea how wide the front sight should be to cover the width of the bull at 10 meters?
Stan

[dulcmr-man]

I have 10 meters in my garage and I shoot a Morini 162ei. Your circumstances may vary. My pistol's front sight is 5mm wide and looks like it is about as wide as a standard 10 meter AP bullseye. I have other front sights but this one seems to work for me. My Morini has three positions into which the front sight can be attached and I have selected the rear-most position as I seem to notice slightly less perturbations in the sight alignment this way.

One can purchase front sights from Morini with different widths, but I am not sure what the pricing is. You may also want to consider having front sights 3D printed by Andrew Berryhill (https://www.precisiontargetpistolgrips.com/). I had some extra sights printed by Andrew but I cannot remember how the pricing compared to Morini OEM front sights.

I hope this helps.

Dennis, aka Dulcmrman

[Rover]

5mm sounds about right, but it depends on how far back you mount it. When I found it difficult to find this width, I learned to live with the widest I could get (having several guns). Not really a problem, though.

[porkchop]

Thanks Dennis and Rover. I have a LP-1, I looked in the box and there's 3 more sights in there, I didn't know why. The fact you can position the sight forward and aft to match the width will help also, I'll be experimenting with this now.
This week I been getting my diopter and aperture setting for my lighting conditions, I didn't know you could do so much to get better front sight focus with them, for me this is fun stuff.
Thanks a lot, Stan

[toddinjax]

Thanks folks. I'm shooting a izh 46m. I recently saw the sight radius listed online as 342 - 364? Is it actually possible to adjust, mine is definitely 364, would love to shorten it a bit.

[Gwhite]

I have two IZH-46M's downstairs waiting for repair. I checked, and both have 4.6 mm wide front sight blades installed. They appear slightly narrower than the target black at 10 meters (for me). I believe that is as wide as the factory blades come, but I would think 4.8 or even 5.0 mm would be better. Given the terrible complexity of the part (not), you could make your own.

Some of the observed size will depend on how long you arms are, and your stance, which will change the exact distance from your eye to the front sight. The width doesn't have to be precise, but having it close to the diameter of the black will make it a tiny bit easier for your brain to line things up horizontally. The human visual system loves symmetry...

[-TT-]

Thanks folks. I'm shooting a izh 46m. I recently saw the sight radius listed online as 342 - 364? Is it actually possible to adjust, mine is definitely 364, would love to shorten it a bit.

The front sight holder can slide on the barrel, but on my AV46M, it can only move about 8mm back before it hits the piston cylinder. The pistol came with two rear sights (2.5, 3, 3.5 and 4mm slots) and three front posts (3, 3.5 and 4mm). I'm currently using the 3.5mm rear and 4mm front, but I use the pistol for training not competition. What size front and rear do you actually have on hand? There's a good bit of slop in the sizes, they can vary by a few tenths of mm.

Personally I'd start by choosing the front sight that matches your size preference relative to your target, hung at 10m or at whatever range you plan to shoot. Don't even align the front post in the rear notch when doing this, just raise in your aiming stance and compare the post to the black bull. If none of the fronts you have seems right, get out the file, the black epoxy, or make a new one. For me, the 4mm post was good.

Then move to a blank white wall, and aim through the rear sight notch. Only compare the visible space between the sides of the notch and the post. If you don't have a rear sight blade that gets you the gap you want, again, get out the file. You may want to make the notch deeper, or wider, remember. A deeper notch can give your eye a bit more light, and can help. Again, for me, the stock 3.5mm rear notch was best. 3mm passed too little light, and 4mm was way too wide.

There are probably various mathematics you can apply to calculate the ratios, but I don't think they'll mean much. Your eye, the lighting, and the bevels behind the sights can really play tricks with you. Go slowly and see what's best for you, your target and your range.

[edit]
And BTW, we don't have to tell you the rear blade screws are effectively reverse threaded, right? Because they're threaded from the front and the slots are cut into the tip, they're righty-loosey lefty-tighty. Also, you don't have to remove the screws from the blade to flip or remove it. Use a 3mm screwdriver. With both screws simply loosened, move the blade fully to the right, rotate it up, then slide to the left. Annoying, but easy.

[toddinjax]

I don't have all the original extra parts as I sold the pistol to a gentleman who coaches teams of young shooters and whoever else wants help. When my shoulder miraculously improved a year later I bought my 46m back from him but some of the parts were repurposed.
Yes I know about the reverse threads; same thing happens in bicycle shops all the time. Someone comes in saying they have tried everything but can't get the left pedal off. It has a reverse thread because back in the days before they did, racers would sometimes have a terrible crash when pedaling as fast as possible and then the pedal comes off!
History lesson: The Wright brothers used to build and race bikes, they were the first to use the reverse thread on the left side. They later had something to do with an airplane.

[masaki]

My 60 year old eyes would love to have a "1 2 1" sight picture because now I have too slim gaps of light on either side of my front post. I currently am not using the widest (4mm) post in my possession as it allows barely any light. I have 2 of the exact same rear sight blades and my machinist brother is going to widen the gaps for me. I have searched several other threads looking for the correct ration to achieve a better sight picture but have found only graphic illustrations of beautiful sight pictures. Can somebody tell me for a 4mm wide front post, just what size gap should be in the rear blade to get something approaching a 1 2 1 sight picture? If it matters the sight radius my a 46m is 36.4m

In order to calculate the front sight post width and the rear sight notch width which bring the sight picture you would like to have, you need to know not only the sight radius but also distances between your eye and the rear sight("eye relief" hereinafter) and distance between the firing line and your eye("eye setback" hereinafter).
In calculating the front and the rear sight widths, imagine a picture projected on your eye's retina, and we can write equations for these width. Please take a look at the schematics below.

In order that the projected width of the 7 ring and the front sight post on the retina is equal,

59.5 / ( 10000 + SE) = WF / ( RS + RE ) ... eq. 0
where
SE is eye setback.
WF is front post width
RS is Sight Radius
RE is eye relief

solving the eq. 0 for WF,

WF = 59.5 / (10000 + SE ) * ( RS + RE ) ... eq. 0a

In order that ratio of the the projected widths of the front post and the rear notch is Ratio,

WF / ( RS + RE ) * Ratio = WR / RE .. eq. 1

solving the eq. 1 for WR,

WR = WF / ( RS + RE ) * Ratio * RE .. eq. 1a

Equations 0a and 1a can be written in MATLAB function as follows.

----
%
% an example of Walther LP500 with M-size grip held by 5'10"-tall Japanese
% male in in-line stance
%

SE = 200; %eye setback
RS = 385; %sight radius, adjustable between -38mm and +2mm
RE = 595; %eye releaf
Ratio = 1.5; %notch width by post width ratio projected on the retina

WF = ap_Front_post_Width( SE, RS, RE);
WR = ap_Rear_notch_Width( RS, RE, WF, Ratio);


function frontSightPostWidth = ap_Front_post_Width( SE, RS, RE)
frontSightPostWidth = 59.5 / (10000 + SE ) * ( RS + RE );
end

function rearSightNotchWidth = ap_Rear_notch_Width( RS, RE, WF, Ratio )
rearSightNotchWidth = ( WF / ( RS + RE ) ) * Ratio * RE;
end
----

following are calculation results for my particular case.

WF = 5.716666666666667
WR = 5.206250000000001

In reality, WF and WR in my real case are little bit smaller than the calculation results and are 5.4mm and 5.1mm respectively. Ratio 1.5 is equivalent to 1:3:1 in toddinjax's scale. For 1:2:1, substitute 1.5 with 2.0.

toddinjax,
If you could give me your eye relief and eye setback, I would be pleased to calculate WF and WR for you and the 46M. I am 71y old, by the way.
regards.

[Gwhite]

Nicely done!

I haven't had access to MATLAB since I retired, but if I get a chance, I would like to convert the calculations into a spreadsheet format so it can run with Google sheets or Excel. It's all ratios, so MATLAB is serious overkill...

[toddinjax]

Madaki,
Thank you sir. I will get those measurements to you when I can get a hand taking them.
Thank you SO much.

[kurak]

As a final thought and supplement to previous answers, you can listen to Dina: https://vimeo.com/669654070?fbclid=IwAR ... _z6sRkcHp8

[Gwhite]

I had some time this evening, and translated Masaki's formulas into an Excel spreadsheet.

Sight Widths.xls

(24.5 KiB) Downloaded 254 times

[David M]

There is a problem with the calculated sight sizes.
Yes, the maths is correct but we are dealing with perceived sizes and different focal lengths and
different levels of focus.
This foresight picture is approx. 70% of perceived blurred target image and has a 2:1 ratio.
The spacing is 1/2 on each side of the foresight.
Good for precision.
Most Standard pistols will have sights from 3mm to 5mm.
On a typical pistol with 150mm sight radius the foresight will be from 3.2mm to 3.8mm, depending on arm length.
Free pistol sights can be from 3.5mm to 6mm.
A 4mm - 5mm foresight will only be used on a long barrel Freepistol usually with a sight extension.
Airpistol sights can be from 3.5mm to 6mm.
Airpistol’s at 10m will have a 3.6mm- 4.5mm foresight with rear sight width to suit your arm length, pistol
rear sight position and what glasses you use.
For Rapidfire open the rear sight out to a 3 to 1 ratio.

[Gwhite]

The size doesn't have to be exact. People have been shooting very well for decades with fixed width front sights sized in moderately coarse increments. The newer pistols with adjustable rear widths are handy, but I doubt anyone at the even highest levels of marksmanship take a caliper out to set their rear sight width. They adjust them until they look ~ OK, and then get back to training.

It's an interesting exercise to go through the geometry & the math, but you'd be far better off spending time training than trying to get the sights width "correct" to a tenth of a millimeter. Get them close, and then worry about fine tuning them after you've got 5,000 pellets down range. You can THEN decide if they need further adjustment.

Some air pistols are really bad, and it's worth trying to fix them. As an example, the front sight on the Diana Airbug is about 2 mm in width, which is really skinny. If you are used to shooting with a 4 to 5 mm width sight, it's very annoying.

[Ade C]

Blimey, all this maths is hurting my head. If I didn't have an adjustable rear notch I'd be inclined to just file a bit and keep looking through the sights till it seemed about right

[Rover]

Blimey, all this maths is hurting my head. If I didn't have an adjustable rear notch I'd be inclined to just file a bit and keep looking through the sights till it seemed about right

Naah, that's too simple and effective for many on here, many who are hopelessly inept with a tool as well. You can tell who they are by their "Born To Suffer" T-shirts.