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(This post is an entry in our spring content contest. If you’d like a chance to win a Beretta APX pistol, click here for details.) 

By Peter Dvornik

The Yugoslavian M59/66 went into production 51 years ago and with the half-life of tritium being only 12 years, a little math tell us that only one nineteenth of the sight’s original brightness remains. If you’re like me, this means you’ve spent numerous hours digging through years-old forum posts trying to figure out how to replace them, to no avail. Whether or not you’ve searched yourself, I may be able to save you some time by telling you how I did it.

Of course not all combloc rifles come with flip-up night sights, but those that do will come in one of two varieties, bearing either tritium inserts or luminous paint. These instructions are only for rifles with tritium inserts.

What you’ll need:

A Paper Clip
3 1.5x6mm Tritium Vials
Needle Nose Pliers
A Tooth Pick
Something Flat and Thin
Black or Clear Silicone

Step 1: Obtain the tritium vials
After a bit of searching I found a website which sells 1.5 x 6mm tritium vials at only $6 apiece. Should the standard green not be tacticool enough for you high-speed, low-drag operators, they also offer tritium vials in red, blue, yellow, orange, and pink.

After purchasing the vials, my shipment was delayed for two weeks upon entering the US. Depending on your outlook you may see this as either one more example of a government agency being incompetent, or the government diligently inspecting a radioactive package. I’m not going to say which direction I’m leaning, but I will say the original seal on the package wasn’t broken.

Once the US Postal Service finds enough time in its busy day to actually do its job, you can proceed to the next step.
But first, a quick note about tritium. While it is radioactive, the beta radiation it releases cannot penetrate skin, so don’t eat it or otherwise ingest the substance and you’ll be fine. That said, neither myself nor TTAG is responsible for any actions you make as a result of reading this article.

Step 2: Removing the old inserts
Now you need to find a paper clip and pliers, then cut and bend the paper clip so that it looks something like this:

Once you finish crafting the paperclip into your sight, insert the removal tool, slide it into the notch on the rear sight and use it to push the old tritium vial outwards. You will encounter some slight resistance, as there is a layer of clear rubber sealing the tritium insert in on both sides. When the vial protrudes from the end of the sight you can use your needle nose pliers to remove it completely.

Do this on both sides and then you can proceed the front sight.

Removing the front sight insert was substantially harder than removing the rear inserts. So do yourself a favor and remove the rubber seal before trying to remove the vial. I did this by pushing the broken end of a wooden toothpick against the seal and spinning it between my fingers to break it up. Then you can use your paper clip to carefully push up against the vial, lifting it out of the hole at the top of the sight. Progress will be relatively slow when compared to the other inserts. Once the vial is protruding from the end of the sight, you can use your pliers to remove it.

Step 3: Installing the new tritium vials
First, find something flat and thin; it needs to be able to fit into the notch on the rear sight. Something like a credit card would work fine, but as you’ll see in the pictures, I used a razor blade which was conveniently located in a nearby toolbox. Place a small bead of silicone on the edge of your credit card (or any other suitable flat object) and push the silicone into one of the tritium insert holes. If you can see the silicone through the viewing aperture then you have enough.

It is important that you use silicone for this procedure as silicone will not degrade, shrink, or harden with age. Using silicone will ensure that your tritium vials will be held in place firmly without becoming permanently attached to the sights.

Next, insert one of your new tritium vials into the outside of the sight. The length of the vial will be shorter than the length of the hole, so the vial will not completely fill the viewing aperture. To rectify this, press your flat object against the inside of the sight and use a straightened paperclip to push the vial through the hole until it comes to a stop against your flat object; this will give you the brightest sight picture. If any silicone was pushed into the viewing aperture during this step, you can use the tip of a toothpick to remove it.

There will now be a couple millimeters of empty space on the outer side of the hole, so to ensure the vial is sealed in on both sides, you can use the tip of your finger to push silicone into the hole. While you are doing this, keep your flat object pressed against the inside of the sight so that your tritium vial does not slide into the rear sight notch.

Once that is done, just wipe of any excess silicone and repeat your work on the other side.

The front sight is much easier than the rear: just push the vial into the hole until it completely fills the viewing aperture and is no longer protruding from the top of the sight, then seal the top with a small dab of silicone, wipe off the excess and you’re done!

All that’s left for you to do now is hurry off to the darkest corner of your house and inspect your handiwork. With my camera, I could not get a decent picture of these sights to save my life, however in person they are bright, clear, and easy to align. What more could you ask for?

Upon completion of this project, you will have restored a measure of period-correct, tactical functionality to your classic military service rifle. officially rendering you the slickest operator in your peer group.

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      • Beta particles don’t care who inhales them.

        Assuming the cheap viles are in fact tritium, your next prayer should be that they don’t blow up in your face upon recoil. But if they do you better not breath or get any dust in your eyes or mouth.

        But please do enlighten us about the safety of cheap radioactive substances sold on the internet and then mounted on a gun. And why do kids these days think radioactive materials are ever safe?

        • Tritium, being an isotope of the element Hydrogen, has a specific characteristic that makes it relatively safe to handle in the tiny quantities in the glass vials it comes packaged in.

          It doesn’t stick around.

          Released into the air at sea level, it makes a beeline straight *up* at a velocity of over 30 MPH.

          Indoors, it sticks to the ceiling. Outdoors, it makes it way to the top of the atmosphere.

          The hazardous radioactive gas you should be worried about is Radon. It collects in areas like basements until ventilated outside.

          So ends today’s lesson, *Doktor*…

        • What Geoff said plus, as a low energy beta emitter tritium isn’t dangerous unless you inhale or otherwise ingest it. If ingested it will form tritiated water which has a pretty short biological half-life so a single exposure, unless massive, won’t have serious long term effects on a person and, in fact, will probably go completely unnoticed.

          On top of that, the amount of tritium in those vials is minuscule so even if you crushed the vials and intentionally inhaled the contents the bits of glass you inhaled would probably hurt you more (and more noticeably) than the tritium. Working with these amounts in a reasonably well ventilated area is perfectly safe.

          As Idaho State University puts it “The rifle sights contain 12 mCi of tritium. If all of its activity were ingested, the CEDE would be 768 mrem or roughly two years of dose from natural background [radiation].” (emphasis mine).

          Your fear of this isotope is irrational.

        • not to mention the vials are only 1.5 x 6mm outside dimension. Volume is considerably less. The radiation exposure is strictly academic. You’ve absorbed orders of magnitude more by walking from your car to your house.

        • I wrote the first draft of this article almost three years ago (and subsequently forgot about it until recently). Since then, i have put hundreds of rounds through the rifle and none of the vials have cracked.

  1. Thanks Dan, I’ll have to add this to my list of firearms projects. Every time I take my Yugoslavian SKS to the range I wonder what it would take to update the night sights. Your article has been bookmarked for my future reference.


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