Introduction: Semi-Auto Longshot 2

Picture of Semi-Auto Longshot 2
Some of you reading this may remember my last shenanigan, there were some issues with the design and I decided to scrap the pneumatic bolt altogether for my second attempt. I honestly have no idea how much the last longshot cost, I kinda just stopped counting after a while. This blaster is still a work in progress, attempting to juggle this project /school/ HvZ/ Senior design is rather difficult. This instructable will be updated several times in the coming weeks, but I hoped that the progress so far would be enough to enter the Epilog contest. Alright enough about this... on to the technical details!
  • Raw materials you'll need:
  • 3/8" thick acrylic sheet (Mcmaster P/N-8774K41)
  • 5/8 Diameter metal rod, I'll explain later
  • #10-32 Soc Hd cap screws (Mcmaster P/N-90128A940)
  • 1/4-20 Soc Hd set scr (Mcmaster P/N-91375A533)
  • #5-40 Soc Hd cap screws (Mcmaster P/N-91251A130)
  • 0.5" DIA X 12" Lg PVC pipe (98 cents at Home depot)
  • .5" x .5" x 1" piece of aluminum/CRS
  • .25 x .25 x 2" piece of aluminum/CRS

This is all necessary to begin the mechanical fabrication, feel free to substitute any or all the fasteners to suit whatever you have on hand as these are just the sizes I used on mine. Just to give you an idea of what we will be constructing see the images below. Next up, manufacturing!

Oh and to give you a taste of the firing rate check this video out, it misfired a few times but that is just because the stepper motor limit switches weren't wired up yet. 

This build was really inspired by Mass Effect 2, I've always loved how the LS resembled the M-15 vindicator style gun from ME2. I know there are definitive visual differences between the Long shot and the M15-Vindicator but I hope that once completed they will look very similar. As the organizer for my universities HvZ game I play as the Commander NPC "Commander Shepard," so i felt that an M-15 vindicator would be a worthy blaster to wield =). 

Here is an update video, the motors are running at 1/4 power which is why the dart velocity is a bit low. Once the boost converter is finished I'll take a video showing it operating at full power.  Enjoy!

Step 1: Flywheel Assembly

Picture of Flywheel Assembly
So you got all your parts together and scrounged for material, whats next? Manufacturing! The key to this blaster being a success is to take your time, when you start to make mistakes stop and take a break. It's better to stop and pick it up another day than to ruin all your hard work and have to start over. 

Below you will find a zipped folder containing bother .iges files as well as 1:1 PDFs. All you really have to do is print them out, stick them on, and start cutting/drilling. But DON'T FORGET THE SAFETY GLASSES.... seriously, hot plastic/metal will permanently injure your eyes. 

You will NEED the following tools:
  • A cutting device (Ie. Table saw, band saw, dremel, hacksaw... etc)
  • A drill press or drill (drill press is preferred)
  • #10-32 tap and tap drill
  • 1/4-20 tap and tap drill
  • Sand paper
The following tools are what I used:
  • Band saw
  • Standard 3 axis manual milling machine
  • Standard engine lathe
  • Dremel
  • #10-32 tap and tap drill
  • 1/4-20 tap and tap drill
  • 1/2 DIA drill bit
  • 27/32 DIA drill bit
  • Sand paper
  1. Begin by cutting out all your blanks, Check the drawings provided. Make sure to make everything as accurate as possible, this will drastically reduce your headaches later on. See the images below of assembly and reference. The PVC breech was cut by hand using a Dremel (Abrasive cutoff wheel and grinding wheel)  and adjusted to fit the magazine and flywheels. The pockets in the carrier plate were designed for these motors (Tamiya Torque tuned motor) but any small rc motor will do. I would suggest that you drill and tap all the holes in the barrel mounts (with the exclusion of the hole for the barrel). Next, drill and counterbore the holes in the main carrier plate.Once everything is drilled and lined up, screw the assembly together and drill/cut the main bore for the barrel to sit in. 
  2. The second phase is to manufacture the flywheels, the reason they are metallic is because you will need to install set screws to keep the shaft of the motor from spinning freely, and unless you are careful you will strip the threads out. I used #3-48 set screws, you could also glue the wheels on if you don't feel comfortable working with small taps. If you do not have access to a lathe you can use the  5/8" diameter rod as it is, and simply use a drill press to drill the hole (It won't be accurate, but it will work). The only issue with using the rod without turning it down is that you will have to alter the barrel more. You don't really need to rough the wheels up or add any e-tape/rubber, they will grab the dart just fine. 
  3. The third step is to make the loading mechanism. This will be slightly more tricky as you will need to machine the OD of the rod down to properly fit inside of the barrel, or simply scrounge for material that fits. The crank and linkage are very simple to manufacture, but the entire assembly will need to be sanded to ensure that all the parts slide freely. Once again, these parts are most easily made from aluminum, but plastic could be used if you can't get your hands on anything else. 

Step 2: Modifying the Shell

Picture of Modifying the Shell

I get a LOT of flak from people for what they deem "destroying" a  Long Shot, however I respectively disagree and i would even go as far to say that i'm doing a SERVICE to the Long shot. Who else can say that they have a LS that has a 120' range? Or one with a 4 round per second firing rate? Well.... besides me =). 

So if you don't want to "ruin" a longshot, go break open a recon, alpha trooper, deploy, or raider and get this working in that shell instead. For those of us who would rather take one of the best looking NERF blasters out there and turn it into something amazing, keep reading!

Okay, so grab your longshot and open it up. Remove EVERYTHING, I decided to cut the front of the blaster off to make it more HvZ friendly; Start cutting strait down at the end of the tactical rail. Take a look at the pictures to see what you will need to remove, honestly it's not much.... well compared to the last build I did at least. 

It's easer to watch the video in the next step to figure out where to modify the shell. I promise it will be easy. 

Step 3: Align the Assembly.

Picture of Align the Assembly.
Now drop the assembly into the LS shell and see where you will need to fiddle around. You may need to remove some of the guides for the original bold assembly, but this can be achieved with a Dremel in a few minutes. 

  • Stepper motor installation depends on which you are using. I had mine laying around from a former project, but any bipolar stepper motor with a reasonable torque will do. You can simply bolt the stepper motor to the plastic LS shell, or even glue it on; I opted to make a plate to increase the rigitidy of that area out of 1/8" thick 6061 aluminum plate. 
  • I decided to cut out the back of the shell and fix the stock in the closed position to increase the handling of the blaster. I attached the stock to the LS shell with one bolt and a bunch of epoxy puddly. 
  • The next thing is to clear the area around the crank, it will depend on where you mounted the stepper motor. As you can see I got lazy with the crank after I realized no one would see it once the blaster is closed. 
And now the video!!

Step 4: Electronics

Picture of Electronics
And now we begin the portion of this build which has caused me the most headaches.... the electronics. 

THIS PAGE WILL CHANGE, as I finish up the electronics I'll update this section to reflect everything i'm doing. I'm sorry the instructable isn't complete; but even if you started working on this thing right now i'd have the electronics/programming up by the time you got here. 

What you will need:
  • Microcontroller of your choice (I used an arduino)
  • Stepper motor controller or servo (I used the easydriver)
  • 3 micro switches, you can get them at radioshack but i suggest e-bay. 
  • one SPST switch for power on/off
  • One LED for status
  • Multi-position switch if you want select-fire 
  • Resistors
  • Batteries (This will be discussed more in the next step)
  • Boost converter (see next step)
  • Motor controller (see next step)
  • wire... wire... and more wire
  • Patience
Here is a basic overview of the system. STAY TUNED FOR UPDATES!!

Wiring diagrams will be available shortly. 

Step 5: Electronics Continued

Picture of Electronics Continued
Okay, so this section of the instructable will be slightly bare temporarily. I'll update the electronics as they progress. 
  • Boost Converter: This circuit is required to give the stepper motor the maximum possible power through the easydriver circuit. The easydriver is capable of providing a maximum of 750mA per step, so to overcome this power limitation we must give the circuit the maximum voltage it can handle in order to achieve the maximum torque from the stepper motor.      

    My first few attempts failed in one way or another, I'm going to try a third time using a new layout which will give me more room to work with on the proto-board. You can see an image of my second attempt below. More to come!!
  • Motor controller: This will be a simple MOSFET driver for the motors to trigger them from the arduino. 

That's pretty much it for the electronics, stay tuned for the programming tutorial once it is finished!

Here is a video showing off the loading mechanism operating at 30v, which will be close to the output of the final boost converter. 

Step 6: Epilog Contest

Picture of Epilog Contest
This page is for anyone viewing my instructable through the Epilog contest. 

A little about myself:

My name Is Philip Haasnoot and I am currently a senior level mechanical engineering student at Stony Brook Univerisity. I am the president of the SBU Solar Boat Team and represent the university on the board of directors for the SBPLI FIRST robotics regional. I am a huge supporter of open source and collaborative projects. My field of interest is medical robotics and prosthetics, to date I have designed several prototype prosthetic arms and dexterous hands that are in various stages of development. I also have constructed two Robo-ONE style robots, even going so far as to design my own servos to fit the form factor better. 

So what would I do with a Zing laser cutter?

It would be easier to ask me what I wouldn't do with a Zing laser cutter. The answer to that question is not much. I've seen videos on youtube of people using laser cutters to slice pizza, or give themselves tatoos; I would never use a laser cutter for these types of silly actions. Some things I would use a laser cutter for :
  • Manufacture parts for my Robo-One style bipeds
  • Develop the prototypes for my prosthetics
  • produce assistive devices for the handicapped
  • Repair things that require unusual parts
  • Assist local FIRST robotics teams with more complex acrylic parts
  • customize pretty much anything
  • Etch circuit boards
  • Finish my open source servos
  • Begin a plethora of collaborative projects

There really isn't much I wont use this laser cutter for. Hope you ya'll find me worthy of your votes!!


lunadude (author)2016-05-23

Just a question, were you a student in FRC, or have you only helped mentor teams, and if you were on a team, how much did it help you with mechanical engineering in college? Currently I'm the number one grease monkey on FRC team 4329, and I was just wondering how much it improves college and real life after. Thanks in advance

uzarnom (author)2014-09-03

Thanks for posting this , i was having trouble with trying to make a semi auto strong arm but this guide showed me some possible solutions. Thanks :D

jcksparr0w (author)2013-08-14

i LOVE the fact that you might let a first team use a laser cutter. i hope if you get it they know what to do with it. very impressive project all around

Nuvasuper (author)2012-10-14

Why do you use a stepper motor instead of a setup where the motor lines up with the piston and can run continuously? I don't know the proper term, but something like this:

wcavanagh (author)2011-11-18

I would imagine using a push-type solonoid actuator would be easier / cheaper (and easier to fit inside the case better) than the stepper motor.

Philysteak527 (author)wcavanagh2012-04-12

Depends on the force required, not to mention solenoids generally have a very short stroke.

Quertyman (author)2011-12-12

I've been looking around for a dremal, would this one work and what tip do I need for it to cut PVC.

curious youth (author)Quertyman2012-04-08

really any rotary tool will work. all you need to cut pvc is a cut off wheel. but try to stay at a low/medium speed for pvc. only because its a plastic and melts at a high speed

Like curious said, PVC melts very easily so you will want to get a feel for how fast you can cut with things like abrasive discs. Although at times it is beneficial that it melts, much easier to clean up a bit of melted plastic off your part with a utility knife than drag out a vacuum cleaner (In my opinion at least).

rickkix (author)2012-01-13

This stuff is awesome. Not to be rude, but why waste your time making a semi? You should try something like making a minigun out of a Vulcan or something like that.

Philysteak527 (author)rickkix2012-04-12

This isn't just a semi-automatic blaster, being it is fed with a motor it can fire in full auto or burst modes.

Check out one of the demo videos, you'll see it isn't strictly semi-auto.

Madmartigan95 (author)2011-08-06

This is amazing. I am totally adding flywheels to mine.
(i have a spectre so this may be pretty odd, but I think it will work out.)
Keep up the ideas, they're awesome!

jumpingcat (author)2011-07-20

i like it pwns

joh54 (author)2011-05-03

You should make a full auto recon
That would pwn

jongscx (author)joh542011-07-01

Just got a recon shell from a friend, I'm workin on that now...

joh54 (author)jongscx2011-07-06


Philysteak527 (author)joh542011-05-05

This system will fit into pretty much any clip system blaster =)

nicwitzke (author)2011-04-25

Do you really need an arduino? Couldn't you just make it have a series of hinges, and only use one micro switch for the trigger

jongscx (author)2011-04-04

An arduino seems like overkill for this project...I guess it's a necessity for the stepper motor, but jeez. Maybe add an ammo-counter that resets when a new clip is added.

I've never been a fan of flywheel systems. I think a nerf gun should use air... but that's just me. How long do you need to wait for the wheels to spool to firing speed? is there where the 4 rps figure comes from? In any case, I love that you have the two variants of longshots, very cool work!

TSC (author)2011-04-04

Thanks for makeing theses there so cool! I would like to build one some time!

Musicman41 (author)2011-03-29

I think I understand your firing mechanism but I am not sure. It looks to me like you feed the darts through two powered wheels. It looks like the turning of these wheels is what propels the dart out of the barrel. Is this correct, or am I missing something, or is something not included yet?

Kaiven (author)Musicman412011-03-29

From what I can see also, that seems correct...

Philysteak527 (author)Kaiven2011-03-30

That is correct, it works on a similar principal to a baseball launcher.

taowyman (author)Philysteak5272011-03-30

what do you think is the hardest nerf gun to mod

Philysteak527 (author)taowyman2011-03-30

Good to hear it cows, you would be surprised at the useful things you can come up with when modifying these toys. Not to mention you can use the skills you learn and apply them to a multitude of projects.

If I had to pick one i'd say the new dart tag line with the built in mags, they are incredibly complicated to even disassemble.

Kaiven (author)Philysteak5272011-03-30

Thought so, it's a very good design, great write up. Actually, after seeing this I whipped out my Recon CS-6. I think I'm going to more mods than I did before ;)

Morte_Moya (author)2011-03-28

Windcalmer from the forum here. This is a really great write-up. I love the flywheel design. Simple and looks to be VERY strong.

taowyman (author)2011-03-27

would you sell this and how much

Philysteak527 (author)taowyman2011-03-27

I'd like to offer some hobby services if I win the Epolog laser cutter. I'd be willing to sell the mechanical portion of this blaster in a kit for about $20-$25, as well as a few other assorted robotics kits.

Other than the mechanical part you should expect to spend around 40-50 on the electronics.

taowyman (author)Philysteak5272011-03-27

cool ill think about getting this and hopefully i can find some more money:P

Iridium7 (author)2011-03-25

Just a little FYI but, This would be fully automatic. "semi-auto" is actually called 3-round burst or just burst. Real semi-auto is just the way it comes stock, can also be called single shot. Not meaning to be rude, there's just a bit of a difference.

l3owzaaaah (author)Iridium72011-03-27

I'm pretty sure with semi auto it's just as fast as you pull the trigger. A single shot is different as you need to prime the gun bolt between each shot. Hence the name bolt action.

zippydaspinhead (author)Iridium72011-03-25

I agree with you in principle... but the accepted 'slang' if you will is that it is originally considered a bolt action or single shot, semi automatic is what you would call an auto-loader, or a weapon that fires every time you pull the trigger, without having to cycle a bullet into the chamber, with automatic meaning to be able to hold the trigger for continuous fire.

Since this is the normal 'slang' I would accept his use of it since 90% of the populace thinks like that instead of the 'proper' way.

If it looks, thinks, and acts like a duck, its probably a duck.

ilpug (author)zippydaspinhead2011-03-25

or maybe its a brant, and the observer doesn't know that.

Philysteak527 (author)ilpug2011-03-26

I agree that this would realistically be considered "full auto," but if you google "semi auto longshot" you'll find my mods. I'm really just trying to get people to see this.

taowyman (author)2011-03-27

this is epic how much would u say it would cost if i have the gun?

ilpug (author)2011-03-25

Amazing gun. I have been thinking along the lines of pneumatics for a nerf mod, but not a flywheel system. I personally think the longstrike is the best gun to mod, because it has a MASSIVE interior space to cram in all kinds of parts.

Philysteak527 (author)ilpug2011-03-25

Got ya covered ;)

ilpug (author)Philysteak5272011-03-25

I saw that one. very nicely done, but a bit out of my price range, and i don't like dabbling with C02, because i have never had good luck with it. I might mod my lonestrike to use your flywheel system

Philysteak527 (author)ilpug2011-03-26

Flywheels are infinitely easier/cheaper to pull off than that CO2 system, not to mention there is alot of room for improvement and performance upgrades are easily installed.

ilpug (author)Philysteak5272011-03-26

yeah, definetely going to do this, but what is the purpose of all the electronics? it seems that the whole system could operate with just a few switches. also, what is the range of this gun?

Philysteak527 (author)ilpug2011-03-26

I've only run the motors at 5v right now, once the boost converter is installed I can run it off of the 8v NiCad packs. Even at 5v it gets 30-32 feet average with stock streamlines, filling the tips with silicone increases range by about 8-10 feet. Can't wait to crank this baby up to full power.

Electroinnovation (author)2011-03-23

I dont mean to be a grammer nazi but just so you know at the bottom of step four your wrote patients. I think you may have meant patience. Anyway I love this idea and hope you win the contest! 5* and sub!

Thank you! I updated it =)

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