Well through periods of being very busy with work and being ill, progress has continued on the Wastelander Rifle design - part 1 is here.

DISCLAIMER: As this now looking a bit more realistic I wouldn’t want anyone getting the wrong idea. This is purely a ‘toy’ rifle designed to shoot Nerf gun type darts using air from an internal piston. Additionally, though I’m designing it to be used in Larp personally, I cannot make any claims about its suitability to be used in such a manner.


Wastelander Rifle Overview


After a lot of tweaking with the design I’ve got a set of internal mechanics that I am happy with.

The initial problem I had was sizing elements based on the volume formula used by Evan Neblett. This was pretty basic and I couldn’t understand why I was getting different answers until I realised Imperial Pipe sizes used in the original are fairly out-of-wack with the actual dimensions. As I was using metric sizes I was getting much smaller volumes from what I thought were equivalent pipes. With that resolved, I enlarged the piston/bolt to give a bigger air-volume and a shorter stroke-length.

This has added some complexity as now the magazine sits a long way below the barrel axis but the feed ramp is pretty shallow and hopefully won’t have any problems.


Trigger assembly...

The trigger mechanism caused me some issues. By the nature of the piston assembly the trigger would have to mounted very far aft of the chamber or utilise a transfer to have the trigger forward and the ‘sear’ could be aft, keeping the chamber, bolt and trigger together. This might lead to a fairly nasty mechanism and shooting feel but we’ll see. I wanted something fairly responsive for accurate shooting and robust so it didn’t need much maintenance. As a plus it would fairly easy to build as I don’t have a milling machine, if I need to do any complicated cuts, then they’d all have to be done by hand.

I took a copy of the model into 2D to work this out as I find it easier to solve mechanical problems without having to worry about modelling in 3D and keeping things constrained. After some playing I went for a retaining peg holding back the piston-plunger, linked to the trigger with a mechanical connection from a tie bar. As I can lock the tie-bar with a simple cam it gives me a fairly easy option for adding a safety catch. Though this will only disable the trigger, so there will be a slight risk a heavy blow might drop the peg but I don’t think that would be too likely an occurrence – and seems to accepted in real rifles. If I find it more of a risk, then I might add a second catch on the plunger itself – currently I like the safety where I’ve planned, as it’s a good position for a thumb catch.


Trigger assembly concept design
Trigger assembly model




Sourcing materials...

With all the details sorted I could source the materials for the project. I’d already decided on the range of pipe sizes I was going to use and got in a selection of what I was planning to use. For other areas I was a bit more restricted and some of the design details had to change to be updated to suit the sizes of materials available. Aluminium bar stock particularly was very limited in sizes I was after, and through I could have used steel I wanted to keep an eye on weight and ease of manufacture whenever possible. Aluminium being much easier to cut and file than steel, brass might have also been an option but I find the cost pretty prohibitive.



Potential problem...

This design is intended to use the streamlined Elite style Nerf darts, and I don’t actually own any. So being sensible I bought a pack just to check the dimensions and properties are as they are listed on-line. For the Wastelands UK Larp I won’t need darts as ammunition is a rare commodity supplied by the system. However… thought I had a big problem when I came to testing my darts the 12.7mm OD dart securely plugged the 13mm ID barrel pipe and refused to budge easily. Without using the kind of pressure that would ruin somebody’s day, it looked like I needed to come up with an alternative material for my barrel. I had some similar sized material in Aluminium tube which I tried for the same problem. Looking around I decided that I need buy in some brass or specialist plastic tubing and build up a composite barrel, which was an additional pain in the ass I didn’t want. However bad practice on my part had made me knee-jerk and look for a solution I didn’t need. Like an idiot I’d only opened the pack of 30 darts and take the first one out to try, the rest I’d put away, on the off chance I got out one more dart to test. Fitted fine, so did the other 8 I tried. Problem averted. Does mean I’ll have to be careful with the calibre of darts I get – oh, well post-apocalyptic hardship and all that. Using the barrel pipe as a blowpipe I could also test the kind of range/flight I was getting for a (lung provided) given pressure. All in all, was pretty good, plus my partner got to have the fun of shooting darts at my head once she saw what I was doing.


Action Spring...

I’m still not sure what action-spring I’m going to need so I bought a load of springs. Originally I was planning to buy a rifle or airsoft action spring but they seemed to cost silly money or come from overseas. Instead I ended up ordering a range of semi-custom springs from a spring manufacturer, over a range of lengths, sizes and materials. Stainless steel are my low power back-up springs should I find the rifle hitting a bit hard with the regular steel springs.

Many Springs

After the experiments with my feeble lungs I’m thinking over-powered is more likely than under powered at this stage but we’ll see. Worst case, if after tweeking the springs it's still hitting too hard, then I have some ideas up my sleeve to make sure I don’t produce some super-canon.


Ready for stage 3...

Wastelander Rifle 02
Wastelander Rifle Rear


Once all the mechanism details were finalised came the stage I’d been looking forward to since the start of the project – designing the actual look of the rifle.