PURPOSE

When 3D printers started to dramatically drop in price and were thrust onto the commercial market, I was immediately hooked. This is every engineer's dream come true! The storm of cool printable products really hasn't developed as I expected however. Most people were, and still are, only printing little sculptures and vases. In terms of pushing this technology to its potential, we're not off to a great start! I came to the conclusion that it is not a lack of vision that is limiting the use of these desktop printers, but a lack of designs. People would print more awesome things if there were more awesome things to print. So I put two and two together and started designing this printable airsoft gun. It's the start of many designs I hope to produce for people who really want more than just a vase from their printers. I hope it will inspire you to get your creative mind in gear and contribute some awesome designs for a 3D printable future!

TOOLS

3D printer (I used an UP PLUS)
epoxy glue (and solvent if you have it)
screwdriver
drill (optional)
pliers
wire cutters
hacksaw

MATERIALS

820g of ABS (just under 1 reel)
nuts and bolts $10
-M3x16mm (qty. ~20)
-M4x38mm (qty. ~15)
-M4x25mm (qty. ~10)
-M5x75mm (qty. 1)
-M8 threaded rod (1m length)
1m of 15mm OD metal tube $10
bike pump $4
spring $8
Airsoft barrel with bucking (approximately 350mm long) $15
spray paint (optional)
small scrap of 20mm PVC electrical tube
2 or more ball point pens (dead or broken)
7mmOD irrigation tube
2x Old couch springs or other extension springs

GUN SPECIFICATIONS

Shoots 6mm bb's (0.2g recommended)
Single shot springer (spring powered)
Chronoed at 250fps with 0.2g bb's
Accurate to 20m, extreme range 40-50m
Weighs a nice 1.2kg
Mag capacity: 11 rounds
Picatinny rails
Adjustable hop up
Working safety
foldable bipod and sights (for scope if desired)

DISCLAIMER______________________________________________

I take no responsibility for your actions with this gun if you should decide to make it, or if you are not legally allowed to own such a gun according to the laws of your country and yet still decide to make it. This is an airsoft gun only, not a firearm, however it can do damage if aimed at the wrong place. Treat it responsibly and use the appropriate safety gear.

That being said I do encourage you to have fun! That's what this gun is for after all.

_________________________________________________________

Step 1: PRINTING

First things first, parts need to be printed and cleaned.

You will need just about a whole reel of ABS plastic (820grams). Haven't tried PLA, it is significantly weaker, but you can try if you want!

Most of the 46 parts will fit within the print volume of a desktop printer (120mm cubed), but there are a few larger parts that will need to be printed on a larger printer with 200mm width/depth and 200mm height. This is inconvenient I know, my next gun will be designed fully for a 120mm cubed print volume. You could split them and fuse them back together with solvent, but be careful about printing too large on an open bed, you may get warping.

The parts are all designed to be printed in a certain orientation for minimal support material, strength in direction of the forces, and also to prevent layers grabbing between parts, i.e. layers are perpendicular for fast moving parts.

Most of the pictures explain the assembly well enough, but I will comment on the design details as we go. If you're confused at any point, have a look at the exploded view animation to see every nut and bolt put together.

Step 2: BOLT

As you will have seen, the piston is actually a bike pump, simple and very cheap, it also comes pre-greased, so no need to look for some silicone grease.

Here's a couple of links to a similar bike pump:

https://www.ebay.com/itm/Mini-Bicycle-Pump-Portabl...

https://www.aliexpress.com/item/32973595341.html?s...

https://www.aliexpress.com/item/32963284075.html?s...

[Links last updated: 15th Sep 2019]

The bike pump needs to be roughly 28mm in diameter to fit in the upper receiver. As you can see, there are two main types of bike pump- cups and o-rings. O-rings give you a better seal at high speed, so get one of them if you can.

The cylinder head should be glued (using epoxy) into the bike pump cylinder which you'll have cut to 68mm long, then the piston head and catch should be glued to the PVC tube which you'll have cut to 72mm long. A 30mm long section of 7mmOD irrigation tube can then inserted into the front of the cylinder head. Finally, bolt the handle into the side of the cylinder head, and voila! Your bolt is complete.

Step 3: TRIGGER BOX

You'll need to savagely rip open a few dead pens and harvest their springs for use in the trigger box and hop unit.

The trigger box can now be put together using those springs, parts you've printed, and a few small bolts (15mm long 3mm diameter thread, and 28mm long 4mm thread).

If you want to know how it works, have a look at the 'Inside the 3D Printed Airsoft Gun' video, towards the end it takes a look at the trigger box assembly and mechanism.

Step 4: MAG

Now to assemble the mag. You'll need to scavenge a mag spring from a broken bb gun mag. I realise this is not commonly found, so in my next design the mag will use a rubber band which is much more easily available. You'll also need a few bobby pins, one of which you'll need to cut down to fit the grove near the top of the right side of the mag housing.

The humble bobby pin is actually made from high tensile spring steel, and makes a great spring for a mag catch, or for any other mechanical parts with a relatively short range of motion.

The function of the mag catches are to hold the mag into the mag well, which can then be pushed in, releasing the mag, by the mag release buttons on either side of the lower receiver.

Another catch sits up the top of the mag housing beside the channel for the bb's. This bb catch holds the bb's in while the mag is being loaded. When it is pushed into the mag well, it is pushed back out of the way by the feed tube that protrudes down about 5mm, allowing the bb's to jump up into the hop unit. This accounts for the satisfying click you'll hear as the mag is pushed in.

Unfortunately the gap between the top of the mag and the chamber means about 4 bb's fall out when the mag is removed, so the mag capacity is actually 15, but 4 don't make it into the chamber unless you tip the gun upside down as you cock it. But this is a minor problem most airsofters will have come across before. In my next design however, I will fix this issue with a more realistic loading style where the bolt carries a round up into the chamber, hence covering the vertical gap.

EDIT 06-10-18:

I've uploaded a modified mag that uses a rubber band rather than a mag spring as they can be difficult to obtain. Check out the zip file named 'Magazine Update- rubber band' which includes all the .STL files for printing, a few images to help you assemble it, and a .STEP of the whole assembly for those wanting to take a look inside- questions are welcome!

Mag Update- rubber band.zip
Download

Step 5: LOWER RECEIVER

As previously mentioned, the lower receiver has two mag release buttons on the sides which are simply pushed into two holes inside the receiver. You may need to do some sanding if you can't remove the all support material inside the holes. When both are pressed, the mag is released and can be pulled out.

The grip is fixed in a similar fashion to real guns, where a bolt is inserted through the base of the grip up into the lower receiver. The vertical slots in the grip prevent any unwanted forwards/backwards motion.

Perhaps surprisingly, the trigger box is not actually fixed into the lower receiver. This is because when the upper receiver is bolted on top, it holds the trigger box in place. In my next design I am leaning towards an assembly with minimal fixtures and no tools required.

Step 6: UPPER RECEIVER

The lower receiver is now all assembled, we can begin on the upper receiver where the real action takes place! (excuse the pun)

There are two fixtures between the upper receiver and the lower receiver, one is a hinge at the front, and the other is a bolt through the baseplate and the stock. The hinge allows the guns internals to be accessed easily, the same idea as the ICS split gear box design.

You'll need to choose a spring now, I used an M130 second hand airsoft spring which cost me about $10 from ebay. You may need to snip your spring down to size so it isn't too pre-compressed.

The trigger must be held down to insert the bolt, just like a real gun. After the bolt

Step 7: STOCK

Time to attach the stock.

One bolt goes through the lower hole on the stock base to fix it to the lower and upper receivers.

You'll need to cut two lengths of 15mmOD metal tube, steel, aluminium, or even copper, doesn't matter too much. They then need to be glued into the shoulder rest as seen above. If you're spray painting, do that first before you glue so you don't have to tape around awkward angles.

One awesome thing about 3D printing: fancy cut-in design patterns actually reduce time and cost to implement, unlike conventional manufacturing processes where this would add cost and time. Less material, less time. It just makes sense!

Step 8: HOP

Moving onto the hop unit now. If you're not an airsofter, hop-up is backspin on the bb that allows it to travel further, the bb literally 'hops up' instead of dropping early. This unit presses a small rubber sleeve down into the barrel so that when the bb passes it, it catches slightly, giving it backspin.

This hop unit uses a slightly angled slide pushing a ball bearing (in this case, a bb) down onto the rubber sleeve so that the amount of contact between the bb and the rubber can be finely adjusted.

The chamber spring prevents bb's from falling back into the upper receiver when the bolt is pulled back and the nozzle comes out of the chamber, something I call 'backwash'. It was a really annoying design challenge as I wasn't willing to fix the cylinder in place and have to pull back the piston itself to cock the gun. But again the trusty bobby pin saves the day!

Step 9: FRONT UPPER RECEIVER

Now to assembly the front half of the receiver. You'll see a large threaded rod up top, this provides strength down the entire length of the gun, and bears the brunt of the force from the piston hitting the cylinder head, so that the plastic doesn't have to, making the gun very durable. But of course, if a part does break, just print another one! Gotta love 3D printing...

The pictures explain how to assemble the gun, but remember to cut another section of metal pipe however long you wish your barrel to be- maybe sniper, maybe assualt, whatever look takes your fancy.

You may be curious at this point as to the style of the gun. It is actually styled after a SCAR-H, obviously not the same, but it imitates the look and feel of the gun. Why the SCAR-H you ask? Just because I like the look!

Step 10: FINISHING TOUCHES

Finally we can add the icing on the cake, our rear sight and bipod. These are simple enough to put together once you've printed off the parts, so I'll leave you to it.

The rails are the same dimensions as a picatinny rail, weaver will also fit. I haven't tried a scope on it yet as I don't own one, but if anyone finds it doesn't fit, let me know and I can change the files.

Step 11: HAVE FUN.

There you have it, your own 3D printable airsoft gun. If this project is a little too big for you, stay posted for my next gun which will require less materials and tools, have more cool features and can be printed on a 120mm cubed desktop printer.

Hope you enjoyed the Instructable, whether just for inspiration, for actually making the gun, or just for a good read. If you were wondering how I got my printing done, it was through Palmer Design and Manufacturing.

A huge thanks to Andrew Palmer there for all his help with the printing. PDM does professional end-use parts manufacture or prototyping, there's some awesome stuff on the website, check it out right here:
https://palmerdesign.co.nz/3d-printing-quote/

I welcome constructive feedback and any design advice or ideas from you guys! If you've got some solidworks skills feel free to make some changes or additions to the files to keep improving them. Designs won't be sold for licensing reasons, so they're all yours!

Thanks for reading

Step 12: Accessories

Thanks to Roy-Tore Hofstad (rhofstad), the gun now comes with a foregrip and a flashlight holder! These accessories really make the gun intimidating. He also made a larger front sight to accommodate a thicker barrel.

Thanks again to Roy for modelling those up, and make sure you print them if you are making the gun!