NOTICE - 3/13/2026
PSA to avoid AKBlasterMod for kits. I've received several reports of plunger tubes from their kits shattering on high spring loads. As they are making kits with no permission or contract there is not much I can do to stop them except issue this warning. I do this for fun, do not put both of us in a court room! Either self-source or buy from one of the linked suppliers.
NOTICE - 3/31/2026
The design has been updated to use the more common 1.5in/38mm OD tubing and o-rings. See changelog for details. If you're looking for the older version using 35mm OD tubing you can find it here:
Ontos is a tryhard primary for the filthy casual, easily hitting 170-250fps. It's low-hardware, low-budget, low-effort, and low-weight - tailor made for, and by, the lazy and the poor. Designed around only one screw size and 9 hardware items total, the BOM is a third the length of comparable springers such as the SBL and the Alchemist. For this, you get the following:
Track-based bearing prime - instead of plastic bearings on a metal barrel, Ontos has metal bearings on a plastic track. These metal bearings are smoother, more robust, and cheaper than plastic contemporaries. A flat track also has more contact area than a round barrel, resulting in a smoother ride. On prototypes, you can't even feel the bearings rolling. This is effectively "linear rail at home" for a fraction the cost.
Quick spring swap - Turn the spring rest a quarter turn and it unlocks for easy spring swapping and spacer tuning.
Lightweight, Self-tensioning frame - With a combination of canted screw bores, unconventional joinery techniques, and a healthy dose of keying features, the frame panels are preloaded against each other without the need for a bar tensioner. The blaster is remarkably rigid despite not using flat bar, and much lighter than designs that do.
Baller Customization - The whole shell prints flat for optimal strength. This also means you can easily AMS skins onto the first layer with almost no purge filament.
Integrated barrel collet - Quickly swap between barrels with no tools.
4-point adjustable stock - Designed with velociraptors and gibbons in mind.
Hardware Kits :
https://outofdarts.com/products/impulse-ungineering-ontos-blaster-hardware-kit
https://ifb.sg/products/ontos-hardware-kit
https://www.etsy.com/listing/4439295947/ontos-hardware-parts-kit?etsrc=sdt
FPS data from Out of Darts:
View the BOM here: https://docs.google.com/spreadsheets/d/1qzT0tVIs3suiX0zi1kpWmCtHs4wsOLovEyUMk5iUWaQ/edit?usp=sharing
Build Guide:
Changelog
Minor Notice - 6/19/2025
Apparently an older version of BackLeft was left in the directory (the correct one was also in the directory and 3MF, so if your blaster went together at all you printed the right file), and the endcap included in the .STEP was also an older version. These files have been updated. Thanks to @Spyder for pointing this out.
6/5/2025
-Another minor tweak cause I'm OCD- slightly deeper counterbore in the priming bar.
6/3/2025
-Added an assortment of different ram sizes. If you normally run a tighter barrel, or your ram o-ring is too loose or tight, give these a try. Find them in the Tuning Parts folder
3/31/2026 -V2.0
Blaster now uses standard plunger tube and o-rings! PT is 1.375in ID, 1.5in OD, and either 150mm OR 5.72in(Talon Claw Spec) length. You can also use 35x38mm tube if you can only find metric sizes. Plunger/ram now use standard 123 o-rings. See BOM for full details. This update is not intended to be a retrofit. Compatibility with V1.X parts is not guaranteed.
3/1/2026 - v1.2
Revised the endcap assembly to eliminate the spring-loaded tabs. The new spring guide unlocks by pushing it inwards and then twisting. This provides more robust locking with no tabs to break or wear out. Note - if you want to retrofit an existing blaster, you will have to reprint BackLeft and BackRight in addition to Spring Guide, Spring Rest, and Endcap. However, if you frequently swap springs or tune spacers this is a HUGE quality of life upgrade!
6/16/2025 - v1.1
Revised the design of Endcap and Spring Rest for more strength. Recommended stronger print settings for Endcap. As there have been no reported failures of the previous Endcap Assembly design, this is a preemptive change. Testing of the previous Endcap Assembly showed that the tabs wouldn't start to bend until above 40kg force, or about 2x the weight of the strongest recommended spring. However, because the breakage of any stressed component in a blaster is a potential safety hazard to the user, I decided, as an engineer, that raising the safety margin as far as reasonably possible would be the most responsible course of action.
6/10/2025
-Added chamfer on Plunger Head because I'm OCD.
-Updated .STEP with models of the internal volume of the blaster to make it easier to design mods/reshells.
-Added Aggressive Seal Plunger Head for air seal tuning. More sealing action at the cost of slightly increased friction.
Nerf Ontos - Tryhard Primary for Filthy Casuals
by Impulse Ungineering · original on Printables ↗
Toys & Games / Outdoor Toys
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Spring Guide.stl
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Spring Rest.stl
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FrontLeft.stl
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Ontos_V2.3mf
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Captive Nut Tool.stl
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