Finisher 3.0 Nerf Blaster

Hey guys,

I needed a blaster for events lasting two or more days — something compact, with at least six shots. One-handed control would definitely be a nice bonus. The Hammershot is a great blaster, but it's bulky and only holds five darts, so I started modding... and ended up with my own, almost fully 3D-printable blaster. And now, I’d love to share it with you!
 

I literally spent hudrets of hours on this design, so if you find it useful — or if you're just curious about what might jump out of my head next time — you can support me here:
https://buymeacoffee.com/ssmithy

or here if you prefer crypto:
https://nowpayments.io/donation/SSmithy

If it happens that you'd like to use this design commercially, let me know in a DM. We'll see what we can do.

The Finisher 3.0 was meant to be a proof of concept, so I didn’t spend much time on cool design. On the plus side, it’s easy to print and fully functional.
I don’t have a chronograph, so I don’t know the exact muzzle velocity — but it’s pretty much the same as the Hammershot.
You can use a stronger spring or even build in mechanism to increase it, but that would make it much harder to reload with just one finger.
Also, I haven’t tested it under that kind of load, so I don’t recommend doing it.

In the near future, I’d like to design some variations and a quick-release holster. In the not-so-near future, I plan to upgrade the design for some proper cool factor—so follow me if you don’t want to miss it!

edit: short darts version here!
https://www.printables.com/model/1315156-finisher-30-nerf-blaster-short-darts-mod

You can see all Finisher retlated models in this collection:
https://www.printables.com/@SSmithy_3054362/collections/2397585

Changelog:

2025.07.15. 
- B01-B04 - adjusted screw slots for better fit.

Required non-printed hardware

You need only few parts you can't print:

• You don't have PVC tube at hand? You can print whole cylinder, tere is not much difference in performance  https://www.printables.com/model/1399118-3d-printed-plunger-tube-for-finisher-3x-nerf-blast

• pull spring: https://www.webareal.cz/webareal-cz/eshop/0/0/5/9420

• main spring: https://www.webareal.cz/webareal-cz/eshop/0/3/5/8878-Pruzina-tlacna-valcova-1-80x14x60x11-obrobeno

If you can’t get the exact spring, here are some characteristics — pardon my Czech :)

I'm working on eliminating the PVC tube and the pull spring too, so stay tuned for the next version.

Assembly diagram

B01_Body L.stl
B02_Body_R.stl
B03_Handle_L.stl
B04_Handle_R.stl
D01_Drum top.stl
D02_Drum bottom.stl
D03_Chamber.stl
F01_Brake.stl
F02_Seal.stl
S01_Hammer.stl
S02_Spring rod.stl
S03_Piston rod.stl
S04_Piston.stl
S05_Cylinder head.stl
S06_Spinner base.stl
S07_Spinner.stl
S08_Hand.stl
S09_Stop.stl
S10_Case.stl
S11_Trigger.stl

Materials:

I recommend printing the internal parts (marked S) from a less brittle material than standard PLA. I make most of them from PETG, and parts S07 and S08 from ABS. The body (B) and drum (D) are fine with PLA.
For the inner parts, use more perimeters—8 should be enough—to make them fully solid. For the body and the drum, 3 perimeters and 20–30% infill should be sufficient.
Mind that F01 – Brake and F02 – O-ring are printed from FLEX. I’m using Fiberflex 30D, which is quite soft, but I believe it could be much harder and still work properly. With 30D, I print the brake solid. If you use a harder material, you can go with 60–80% infill to keep it softer.
You can replace the brake with a block of rubber, but the O-ring needs to have fairly precise dimensions.

Since the parts are quite small and under some stress, print orientation is something to pay attention to. This is how they were intended to be printed, including supports. The amount of support needed may vary depending on the material used.

For drum chambers I'm using spiral vase, otherwise the inner surface of cells isn't smooth inaf and seams gradually damages the darts. 

Assembly

1. Insert nuts – I tend to make the slots quite tight and slightly heat the nuts by lighter before inserting them. That way, they stay firmly in place — though it takes a bit of skill to get them in.
   You can place the nut on a long bolt or helical rod to heat it and insert it into the slot more easily, without burning your fingers.

2. Insert the pull spring

3. Assemble the trigger with the spring and the M3x20 bolt. Insert the brake

4. Assemble the hammer with the piston. You need to lubricate the O-ring before placing it into the cylinder. I'm using simple vaseline.

5. Assemble the cylinder. I'm using SM-polymer glue, which also works as a putty and stays rubber-like after drying. Try to fill the gaps completely. You can use the same glue to attach the EVA seal, but make sure both surfaces are a bit rough. Use sandpaper or any blade to scratch them slightly.

6. This is quite self-explanatory :)

7. dtto

8. Now the mechanism should be working. Try pulling the hammer and check if the trigger functions properly, and also if the S08 pulley that rotates the spinner moves accordingly.

9. Assembly the drum. Insert nut in this hole under one of chambers. Insert chambers, then the bttom, and then the spinner with bolt

10. The chambers should sit tightly in the drum after assembly. If they rotate freely or rattle, try printing them again with a slightly modified Z factor, or add some MS-polymer glue to the upper part. However, be careful not to make the chambers sticky on the inside.

11. Insert the drum and test if pulling the hammer rotates it. It should move freely. If not, check the mechanism and the body where the drum might be rubbing. Grind down any irregularities or tight spots.

12. Assembly the body. Check the smoothness of mechanism again.

13. insert nuts into the handle

14. Insert the spring and the spring stop. If you're using a weaker spring than recommended, you can try using a different slot for it.

15. Final assembly. Chcek smoothness and fit of all parts one last time and do final grinding if needed.

16. You did it! You’re armed and dangerous now, Sheriff!

And of course, be careful and aim only at non-living targets ;)