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Fiber Optic Sights for Pneumatic Speargun

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.

Would you consider making a sight like this for your pneumatic gun?

  • Sure!

    Votes: 8 88.9%
  • Not worth the hassle

    Votes: 0 0.0%
  • Maybe, perhaps, not sure...

    Votes: 1 11.1%

  • Total voters

Diving Gecko

shooter & shooter
Jun 24, 2008
Due warning - another long thread/build-log coming up.

So, as you may know, I have experimented with adding a fiber optic sight to my airguns in the past.
Why, one might ask? Fair question, I'd say. And though I wish I could group my shots within 5 cm at 5m - and do it pretty much instinctively - that's just not the case. I dive and hunt a few times a year and with the long breaks, I don't like to spend days each time to regain my aim.

So, I am hoping a fiber optic sight can help me a bit in that regard.
My first attempt was using an existing product made for shooting turkey with a shotgun. Please welcome the Truglo Gobble Dot Universal Dual Color (yup, nothing less does it...):

The rear sight is tiny but the front sight is kinda OK. I think the rear fibers are 1.5mm and the front is 3mm total. They also make a version where the front is a solid red. These sets can be had, I think, for about USD 16 and are some of the cheapest fiber sights you can buy.

I ripped one off on my very first outing but then superglued the second one in place and that has held up nicely. I liked the idea enough that I wanted to make my own.

I would have loved finding a slightly thicker fiber than 3mm but the place I got mine from had nothing in between 3mm and 6mm. I am going with 3mm for now, as when handling the 6mm it just seems very bulky. That said, when placed at the front of a barrel and aimed at the imaginary fish on my wall (I have a whole school!) the 6mm dot actually doesn't obscure too much of the target. So from that viewpoint, 6mm is actually not too bad.
I think the sweet spot is about 4mm. It will give a nice big dot to look at while still being small enough that the sight itself doesn't become too bulky physically. I might try to get some 4mm fibers from here or here.

But on to the build log. Basically I am imitating what Truglo did with the sights from above and embedding the fiber in a tube.
For the front, I went with a 5x3mm (OD x ID) poltruded carbon fiber tube. Going with the poltruded tube is not ideal as all the carbon is unidirectional along the length of the tube which means it can split quite easily in that direction as well. But we will see..

First I covered my carbon fiber tank in transparent packing tape. The tape will give a smooth release later on. I then used a bit of mold wax under the tank to make sure it didn't roll around and tacked the small tube for the sights directly onto the taped tank with superglue - checking the height from the table edge with calipers.
It makes sense to just do a long length of tube in one go and then cutting it up for multiple sights later on. Also, the longer length makes it easier to get it aligned properly.

Next step was to make a glue fillet on each side of the sight tube. This will give the sight a contoured base that will align easier and offer more area when glued onto the tank later on.
I would normally used thickened epoxy resin for this but wanted to experiment with some thick epoxy putty instead. This comes thickened in two parts and you massage them together. Normally the A and B parts have different colors, but this didn't so I added some black pigment. Adding it to one part first before mixing the two parts helps you see when you have mixed them sufficiently. Also, I wanted the final mix to be black.

I think the putty is a tad too thick to be ideal, but it did work out kinda OK. Next time, I will probably make my own and make it slightly less thick. The working time for this was pretty decent whereas some of them set up in a few mins, I probably had 15-20 mins with this brand.
Still, since I have not used this product before and was covered in putty and pigment, I didn't get to take pics of the gluing process.
But it's pretty easy, just make a small roll of putty and push it into the gap between the tube and tank. And then, here's the trick - soapy water is your friend! Splash a bit onto the glue and you can work it without it sticking to your fingers. Finally, find a rounded spatula of sorts with an appropriate radius and drag it along the seam to make a nice fillet. Again, add a bit of water when you do this.
The result will look something like this. Mine is a medium in the esthetics department. With a thinner putty and more care, you can make some very pretty fillets;-)

Once set, the packing tape makes it easy to lift it off.

For now, you can leave it on and use it as a guide when adding the rear sights (if you want rear sights). But I will get back to that later, as I work on the rear sights.
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Instead, I will jump a bit ahead in time (my rear sights are underway, so I could take off the sight tube and start working on it).
Cut a piece of the tube to desired length and remove as much material from the top as you feel confident about. The fiber will "suck" light in from the sides and then push it out the end. So the more fiber you can leave exposed and the longer the rod is, the more glow you will get out of the end of it.
This one is just a quick try out, so not really sanded super nicely - just a quick and dirty go with a Dremel like tool.

If you let the fiber protrude slight out of each end of the tube, you can mushroom the ends with a lighter and lock it in place like that. But I wanted the rear of the fiber to sit inside the tube (will get back to the thoughts behind that later on) so I just tacked it in place with a drop of super glue at the front.

Here are some shots of how it would look mounted.

And a shot of the TruGlo sight next to the GeckoSight;-)

The TruGlo sight used to be mounted with half of it overlapping the nose cone (which is why you can see I cut off the original plastic sight on the nose cone). But while this gets the sight placed slightly better it makes it a whole lot more fragile during disassembly and servicing where it will stick out in front of the tank and also interfere with getting a good hold on the nose cone. These fibers are actually just acrylic so they are very brittle and you can see my TruGlo sight has cracked in the middle already. Place the sight behind the nose cone if you want to play it safe.
Also notice how I have angled the back of my new sight so any shooting line can't get stuck on the sight. That's actually how I lost my first TruGlo sight.
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This will be very nice and powerful spear gun! You will be using UBL kit if I am right?
Thanks Tomi:)
Yeah, the plan is to mount it with the UBL muzzle but perhaps Dima will make a second one which can take a bigger range of spears so I can test this gun with 7mm, 7.5mm and 8mm spears and keep the same muzzle. The one I have is optimized for 7mm spears. It's a very slight compromise in the muzzle making it "universal". It will mean that the smaller sliders will be 1mm bigger in OD to still sit centered in the nozzle. So, basically all the sliders will have the same OD as the slider for the 8mm spear.
One way to go about it, is to have a smaller nozzle (front half of the muzzle) for the smaller spears.

I am working on the rear sights. Ideally they would be adjustable, but they wont. I just need to keep them simple and sturdy and once I have a good enough calibration of them, just glue them in place.

Should have some more pics of the rear sights tomorrrow. Had to do some epoxy work, so it's curing overnight.
I fitted the same sights on my original mamba 90! I spent some time searching the forum for the thread but no luck so far....
Anyway it worked ok ish in the shallows but the red colour faded very quickly as soon as I dived.
Of course we don't have very clear water or bright light around my way!
I've had a few attempts using rudimentary sights on the one air and airbalete. I found when I took them off and just simply pointed the gun and looked where on the fish I wanted to hit it's incredibly accurate out to 7 m+. I think I've only missed 1 fish out the last 14/15 I've shot recently.
I think it's quite easy to start overcomplicating things and fir me at least going back to basics really helped. The one air is almost clinical to hunt with - it's super fast and really incredibly accurate.

Sent from my E5823 using Tapatalk
Any way that you could use a fibre optic "light pipe" or (several pipes) to transmit light from a strategically located led source to the sights? I generally use "point and shoot" or "intersecting line" shooting where you consider your sight line to the target and the projection line from the gun which, with experience, automatically accounts for known drop over distance. However I look through the back of the gun for long shots on sitters and there you need to know if the gun is aligned, so I check out the front and rear sights for alignment with each other or that the gun body just presents a disk when viewed from the rear. Illuminated sights such as you are working on could be useful, particularly if you have side sights as well. Note that side sights have been used in the past, often as a stripe on the side of the gun. In fact my "Sten" has a long black stripe of "Dymo" labelling tape on its grey tank on the LHS for that very purpose. The Salvimar "Predathor" carbon tank gun also has an aiming stripe. Maybe such stripes could be subtly lit or a series of illuminated dots or stripes provided with the plumbing for the lights buried in a carbon fibre wrap overlay.
How cool that you used the sights, too. I wonder if it was one of those "forgotten memories" where I had seen your thread and then totally forgotten about it until I thought the idea was my own, haha? Well, I know of one crazy good, and deep, Corsican spearo who has fiber installed on the front.
Yeah, red is the first color to disappear with depth, but supposedly not so much for fluorescents. At least that's what I read. I had no issue as far as I recall with the red the first time around. But I actually have green in all the proper sizes, too;-)

Gotcha. But in all honestly, it normally takes me 2-3 days to find my aim again. I only spear once or twice a year on vacations, so it's simply too much time to waste. And I like tinkering. If these sights help, then good. If not, then I had fun making them;-)
Thinking of it, I actually think I am the most accurate with my One Air. I have successfully taken some incredibly long shots on medium sized fish and smallish jacks. I aim down the left hand side of that gun. Rarely fails. 'Clinical' is a super description and I can totally relate, it really does feel like hunting with a scalpel.

Sure, you could add a fiber optic end glow cable being lit by an LED. But if I was to add a power source, I think I would go all the way and have it power a laser...;-). But even I think that is possibly overkill;-). Would make for a fun project though.
At one point I actually designed a wrap around camo sleeve to be inkjet printed on sticker vinyl. I had a pic of a brownish piece of reef that I used as a background and wanted to add a white stripe down the middle, too. Would have been pretty easy to do and could have covered it all in epoxy or 2-pack auto top coat for protection. But then, I went for the carbon fiber tanks and couldn't get myself to cover the weave, haha.
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Now, for the rear sight, which is almost done now.
Basically, the MO was the same. Tape up the handle with packing tape. Super glue the tubes in and then use epoxy putty to make the base/glue fillets.

The rear sights are smaller. I have both 1.5mm fiber and 2.0mm vs. 3mm for the front. For now, I am leaning towards the 2mm. But the poltruded carbon fiber tubes in these smaller sizes are just too fragile and will split too easily so I went for some thin-walled stainless steel tubes, which might be called pipes in metal...? I will stick to 'tubes' as that's the word I have used for the CF ones;-) . I had these already for my attempts at splicing thin dyneema. From the bunch I had, I choose a 2.5 x 0.2mm (OD x wall thickness) tube.

The thing to look out for here is that the base between the two tubes should be as deep as possible to not interfere with your sight line. The width between the two rear sights decides how large a target area is inside the rear sights at a given distance. If you make it too narrow, I would think it would be too difficult to even get the front sight lined up between the two rears. Too wide and they wont offer much guidance.

You can do a bit of trigonometry or you can do a very simple practical experiment to find the width that works for you. You don't need to take the front sight into account for this (unless it is very, very big). Find a piece of paper and mark out the size of the target that you would ideally like to see within the rear sights. It could be 1/3 the size of the fish you commonly hunt, it could be a specific size like 10cm or you could also just find an item at home with the correct size. Place the paper, or tin can or what ever else you will use for the target size at, say, 5 m. Now, grab a ruler and hold it out in front of you with a straight arm. Hold the ruler perpendicular to your sight line and imagine the ruler being the rear sights on your gun. Take a reading on the ruler that corresponds to the size of your target.

I went for something around 6-7mm. This will give me a target size of about 11cm at 5m from the tip of the spear on my Mirage 125.
This means, as long as my front sight is somewhere within my rear sights, in theory I should land a shot within 11cm on the horizontal plane. Of course, reality is different;-)
We will see if I made the rear sights too narrow. If it is too difficult to even get the fronts within the rears, I think it will be stressful.

Let's look at some pics;-)

As mentioned, I used steel tubes for the rear. This gave me the opportunity to curve the tubes. I am making two sets of rears. One for my Hunter handle and one for the Mirage.

The Hunter handle slopes down quite a bit towards the end, so for that handle I am curving the sights up.

The Mirage has a lot less slope, so I am just going with straight tubes for that one.

In these pics above, the sights are tacked in place with super glue. Once again, I didn't take pics when making the glue fillets. But it is the same procedure as described for the front sight. Remember, soapy water is the trick:)
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After the glue fillet had set I thought I was ready to get on with the trimming off of the excess material but I encountered a slight setback. The epoxy putty didn't bond well to the stainless tubes. I had sanded and degreased them but little had it helped.
So, I went on to cover them with a layer of 200g carbon fiber.

Adding tape to the sides of the carbon helps in avoiding fraying.

Here it is on the Mirage, tacked in placed with some light spray glue prior to brushing the resin in.

Again, once I have epoxy around I kinda stop taking pics - prolly cuz I finally upgraded to a new phone;-). But below, you see the Mirage handle in my home made silicone vacuum bag.

The vacuum bag really helps keep the fiber in place. And the silicone bag is so much easier to use than normal bags.
The dark dots are excess resin being sucked out through the blue perforated release film and into the bleeder ply.
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After an overnight cure, the bag comes off.
You can see the perforations in the blue release film which helps get rid of excess resin. The white cotton like bleeder ply absorbs that excess whilst also making sure the vacuum is evenly distributed.

The release film, as long as it doesn't crease, will leave a pretty nice surface on the laminate.

For now, we end with a few pics of the rear sight slightly trimmed.

Next up: To cut out the middle parts so light can reach the fiber and do some cosmetic sanding.
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DG: "Sure, you could add a fiber optic end glow cable being lit by an LED. But if I was to add a power source, I think I would go all the way and have it power a laser...;-). But even I think that is possibly overkill;-). Would make for a fun project though.
At one point I actually designed a wrap around camo sleeve to be inkjet printed on sticker vinyl. I had a pic of a brownish piece of reef that I used as a background and wanted to add a white stripe down the middle, too. Would have been pretty easy to do and could have covered it all in epoxy or 2-pack auto top coat for protection. But then, I went for the carbon fiber tanks and couldn't get myself to cover the weave, haha."

Laser sights have been tried, but projecting a line in the water needed a very powerful unit and although they were available it was their misuse by other users in "applications" such as shining them in pilots' and truck drivers' eyes that saw them banned here and elsewhere. The "Seabear" had a laser sight fitted as an optional extra, the laser pointer unit was made in the USA, while the guns came from the "Pirometer" factory in Russia. The laser sights were supplied in three different power levels depending on the clarity of the water in which they were to be used. They sat on a slim barrel bracket and had a toggle switch in the rear to turn them on and off. They were nearly as expensive as the gun to buy and from memory Ray Contreras used to sell them as he bought up a lot of parts inventory after the Most Atlantic Company stopped trading, they being the "Seabear" importer for "the West".

I only suggested a light source as in some situations there is often not much illumination, say on an overcast day when underwater there is a leaden grey look to the marine landscape.
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Danish guy did it and made it work for fun. Not that powerful a laser, actually.
The only issue I see is the hassle of making it plus a beam in the water might scare off some fish.

I did shoot a snapper in some quite murky water with the TruGlo sights at about 12-14m. I think the sights showed up OK. Now, looking at this pic (which I had kinda forgotten about) it looks like I could def go bigger in the fiber diameters. This, I think, is 3mm at front and 1.5mm at rear.

Also, a pic showing why I don't want to have the new sights protrude forward of the tank.
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I just found the price list for the "Seabear" guns and lasers and have attached it for everyone's info. I knew that I had seen it recently and had resisted the impulse to throw it away during a recent clean out.
Seabear laser sights.gif
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So, to finish off the build log for now here are some pics of the finished sights with cut-outs. I will make a few more front sights and install green fiber in those and keep red for the rear sights.
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Looks great - when will you get to test the sights out?

Sent from my E5823 using Tapatalk
Looks great - when will you get to test the sights out?

Sent from my E5823 using Tapatalk

Have a trip to the Philippines come up in a week. It's mostly work - I'll shoot a small promo video for a friend's dive shop. But I do hope to find time to A). Drop in the pool and do some target testing and B). Go freediving and spearing for a day or two.
Large parts of the Philippines is quite overfished and a lot of locals spear too so the reef fish know what to expect from a dude with a stick. But we will see...;-)
They might not be so smart about what to expect from a dude with a pimped up pneumatic :) look forward to hearing how it goes

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Well done! The "glow" sights look very nice and I wonder if such devices may appear as either an add-on or a feature of a production gun at a future date. I think that forums are often scanned looking for ideas by production gun designers hoping for a new twist to freshen their product offerings. To my knowledge only the "Cyrano" in its original form had a fluorescent green front sight which tended to fade as sun exposure bleached and whitened it.
Well done! The "glow" sights look very nice and I wonder if such devices may appear as either an add-on or a feature of a production gun at a future date.

Thanks a lot!

I think that forums are often scanned looking for ideas by production gun designers hoping for a new twist to freshen their product offerings.

Yup, I agree. I do think the naming of Salvimar's latest 'Vuoto Dark Side' came from keeping a tab on forums. Supposedly, a Salvimar dealer in Denmark even alluded to that;-)
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