Rifle Scopes 3D Printing Custom Turrets For A Riflescope

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Minuteman
Sep 23, 2019
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I've had a USO SN-4 scope for a while. Those are the old school ones from the times when USO was the nice all American brand and made tanks of a scope, but the most interesting thing for me in this scope was the reticle. It's very intuitive and easy to work with. I'm not sure what the reticle is called, but I'll post a picture below. The problem I had with he scope is that it has MOA turrets and I prefer mils since I'm used to it since the days I've been using it professionally. Although I don't need it for work now I still don't want to learn and memorize new dopes. So I decided to sell it, sold it to a buddy and he had the problem of not knowing any dopes. That's what gave me the idea; what if I print a custom turret for it that has drop marks in meters? So I've done it. If you have the equipment, this could be a thing to take a look at since I've looked for custom turrets for the scope for over a month and could not find any.
I'll post the pictures of the scope and the reticle here and the design and printing process in the next post.
 

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So:
To have a good quality result I first had to decide on the tools to be used. As far as the reverse engineering of the original turret all I needed really was a simple Sterrett caliper to take all the measurements and Solidworks to design the 3d object, but the same can be accomplished with any parametric CAD like Fusion and descent precision measuring tool. When it comes to the printer, the choices are kind of limited. Although I've got a few high end FDM printers, for this one I definitely had to use a resin SLA printer. And it would be really good if it was a true SLA and not the LCD ones, otherwise the resolution won't be enough to make clear markings on the turret. Luckily I've got a couple Forlab printers that are true SLA and can go down to 25microns.
Next I had to decide what markings I need in it. Initially I wanted to go just by hundreds of meters but then revised it by adding the MOA marks as well so some MOA calculations would still be possible. Ideally I would have both, but the turrets have covers, so I'm not sure if they are waterproof. If I made both markings, the turret would have to be larger and I wouldn't be able to use the turret cover. The scope has 48 MOA travel per revolution, so I made 48 tick-marks and made the ones that were the drops for 1-8 hundreds of meters longer for markings. Another thing I decided to add is the bullet info, click value and the meters as distance.
For the load type I decided to go with the regular M855, but you can do any load really if you know the drop. I went to JBM ballistics and calculated the drop for the M855 at 2000ft elevation in MOA and translated it into the cad model.
The turret on this scope is 2 pieces, but after looking at it and not finding any reason I should keep it the same I decided to update the model into a single piece.
After all was said and done I double-checked the dimensions on the CAD model and sent it to the printer to print. Due to the way I had it set up post processing was not a huge deal and once the Print went through the washing and curing station, I ended it a bit and applied the paint for the markings. The resin I had in the printer at the time is Gray, and the only paint I have for markings is red, so I had to make do with what I had. But this can be accomplished with many different colors really. The best probably would be the combination of black resin and white paint. It was also suggested to me by a buddy that I can use glow-in-dark paint for the markings, and I don't see any reason why not, especially if it's white. After the part was ready I tested the strength and the finish and installed it. The finish, you'll see in the picture below, the operation was identical to the original turret and as far as the strength, the part was more than strong enough for the application, so I don't have any worries of it failing in the file, especially with it being covered.
So, in short, it was a success and I actually intend to keep the scope now, since I can use the combination of the reticle and the turret for fast and effective solutions. In the feature I will probably make a few more turrets for other calibers and weights and possibly a turret for the windage with MPH markings to make it even faster. Here's some pictures of the final part. Hope you like it.
 

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Gas

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So I decided to make a windage turret too. I was not 100% sure how to do it, so didn’t think long and made it for 10mph full value cross wing for distances of 300, 500, 600, 700 and 800 meters left and right. That being said, if anyone has a better idea to make it more convenient, let me know.
To be honest I wasn’t even sure wether the windage should be changed, but I have the equipment and it should make the solutions a little faster in wind, so what the hell)
 

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