Good evening all,
I wanted to share my 20x102mm "destructive device" gun with the board, now that it is 100% completed. I made a post or two on here about it before when it was partially complete.
This is the second firearm I have have ever made that is 100% of my own design. While very simple, it is very large, and I think very well-constructed. I bought a barrel from an M61 vulcan gun off of gunbroker for $940 some time ago. I then submitted a Form 1 with the ATF to build a Title II "destructive device" gun, with the $200 tax paid of course. I built this thing up in about 3 or 4 month's worth of spare time in the gun shop. Everything was made from pieces of steel and tools bought off eBay. All the machinework was performed in a Grizzley G0509 lathe, and a G9901 mill. I suspect I have about $2500 total into this project, between the barrel, NFA tax, and tools. Not included in that figure is the ammo (not exactly cheap, or easy to find), or the tripod and T/E mechanism (which is borrowed from my semi 1919A4 rifle).
The N64 controller is the "remote control" to light off the gun. The cartridges use electric ignition, instead of percussion found in all small arms cartridges otherwise. It uses two CR123 volt batteries to feed a boost converter, that makes 300V DC that is stored in a flash photo capacitor. Pressing the L+R trigger buttons dumps that current into the primer.
Please enjoy this short video:
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Great job dude, glad to see it finally panned out to completion.
This guy, everytiem
I don't really have much... I have a few crude drawings I made in Macromedia Flash MX 2004... but after about the halfway point of the project, I just started winging it.
Yes, the falling block seemed to be the simplest, and most robust. The hardest machining operation of the entire project however, was cutting the rounded inside corners at the very bottom on the breech block recess. That was a very looooong and thin end mill to do that. I was biting my tongue and praying that the tool wouldn't break when making tiny 0.01" passes at a slow speed.
I would highly recommend it.
Very nice OP, your thread is an oasis among shitposting and /k/ faggotry.
Post pics of the action and breech. I want to see how its loaded and fired. I am very interested in this.
Also today OP is not a faggot
But why do you NEED a 20mm cannon?
Just kidding OP, this is awesome. Do you have any plans for a more stable mounting system? I'm imagining something like this mounted to a backyard deck or something.
Nothing home-made at the moment. I am trying to finish up my Barrett MRAD rifle, but I wouldn't call it a "project", since there is no gunsmithing work to be done, short of re-finishing it's suppressor to match the gun. I am considering tryign to do a .22lr pen gun inside a sharpie marker, or possibly the "Ballistic Fist" from Fallout. Both of those would be mostly time, and not a lot of money, which is appreciated sometimes. Both of those would be AOWs on Form 1s.
Correct, here is a picture of it in the raw. I'm waiting on my buddy to get me a new "professional-grade" photo of it in it's current form, which is DuraCoat SL - Matte Black. Once again, I made every part of this gun, except the barrel. The barrel itself was scrap from a PS90 SBR project at the shop. I cut it down, and threaded down ends.
Laser Printer. Kyocera EcoSys FS-4020
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I'm still waiting on the other high quality photos from my friend that show those details. I'll dig the gun out in a bit and take a few pics of it with my cell for you shortly.
I have no plans for such. It may recoil like hell, but that is after the bullet gets out of the barrel. When we shot it this past weekend, I was about to hit a log about 14" wide and about 16" long on every shot. The bullet is almost completely solid steel, so it just drills a neat hole through it. I'm satisfied with the M2 tripod (not to be confused with the tripod the M2 machinegun uses, which is the M3 tripod).
No trigger, I didn't want my body being anywhere close to this thing when it goes off. Even if I wanted to put a trigger on it, it would be nothing more than a button anyways, since the cartridges are electric.
Correct. As long as the weather isn't "constant freezing rain", like last winter.
I'm not a robot
ever take the burrs off
OP, let it be known that you're not a faggot.
Here ya go. Here is a pic of the breech of the gun. The chamber and bore is fully chrome-lined, but the back part of the chamber got covered in DuraCoat when finishing the gun. I couldn't exactly mask it off with the extremely awkward way I had to hold this thing while painted. The hole in the middle of the breech block recess is for my "emergency extractor" thumbscrew, in case the block gets stuck after firing. The hex-head counter-sunk bolt behind that holds the adapter for the T/E mechanism in place.
Same thing, but with a live round fully seated in the chamber. Please note the two rings on the primer. The inner ring is where the charge is delivered two. There is a thin ring of plastic that electrically insulates it from the rest of the cartridge (and subsequently - ground). It is called an M52A3B1 primer, fyi. These are not sensitive to percussion.
Beautiful work there. How does the electrical ignition work? One wire/probe on the center pin and another on the casing? I don't imagine polarity matters.
I like that N64 controller. Got any pics of the insides? Make the boost converter yourself or use the circuit board out of a disposable camera along with the capacitor?
I used to use those to make coilguns and stuff in middle school, fun times.
Here is the breech block. It is cut from the same piece of steel as the receiver (3" dia round stock of plain ol' 4140). The breech block contains the "electrode" that delivers the charge to the primer. The electrode is made from grade 316 stainless steel, which was actually a 3/8"x3" bolt bought from the hardware store. The electrode is has light spring tension that extends it by about 0.03" from the breech face, to keep light contact on the primer. Inside the breech block are two plastic bushings made from acetal/delrin (high-tech space plastic) to electrically insulate it from the rest of the block. The chain is attached up top with a grade 10.9 M6x1 bolt.
Here is the back of the breech block. The rear of the breech block transfers the recoil to the receiver. My estimations for bolt thrust put it at about 38,400lbs of force that this block has to absorb and transfer. It takes that estimates 38,400lbs of force, and distributes it to about one square inch against the receiver. That one square inch only counts the flat, parallel surfaces. There may be slightly more surface area doing the work, since there is a 1/8" radius on all the edges of the breech block to mate with the inside of the breech block recess. While I am no engineer, I am well-aware that inside corners are "stress concentrateos", and a bad idea for a gun of this design. If I used 90' corners, the receiver might develop cracks after only a few shots.
I wasn't aware of such a thing till now.
The barrel had it's locking lugs for the M61 vulcan gun cut off, and was threaded 1.75x10RH. The front of the receiver was threaded to match.
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>"Aircraft" less than 254 lbs empty
>Add large wings or a parafoil to reduce stall speed to <25 mph, and a single seat
>Ammo is now fuel; as long as it's <5 lbs you're fine
>"Aircraft" now qualifies as Part 103 ultralight
>Ultralight aircraft in the US require no certification, no pilot's license, no registration and no flight plan
Close the Part 103 loophole!!! Think of the children!
So... the story behind this is that one day I was pissing around on eBay, and found a brand-spanking new M6x1RH SOLID CARBIDE tap for like $10 #buyitnow plus $2.95 shipping. Ever since that day, even single "medium" sized hole I need is done in M6x1, since the tap will rape steel like it is made of butter. Even somewhat hardened steels like 4140 pre-hard, and 75% thread engagements are fodder for this magical tap. It is my FAVORITE tool I have even bought.
This picture shows the T/E mechanism adapter. It is made from a bar of yet again 4140 steel. There is a deep grove in the receiver with radiused corners that this piece drops into. It is held in place with a single 3/8" bolt from above (shown in earlier pic). The stainless steel 8-32 screw is used for electrical ground back to the remote. The current travels from the inner ring of the primer to the outer ring, to the cartridge case, to the chamber, to the receiver, and ultimately back to this screw. I chose stainless so that way it wouldn't corrode over time, since it has to remain raw for the best electrical contact.
Needs to be semi-auto. You can mitigate recoil by stealing the dual gas piston design from the AK-107 (as one piston travels rearward, another moves forward, this counters the recoil completely in smaller platforms so in theory...)
Goddamn OP, this is pretty fuckin raw. I'd really like to see the inside of that controller. Someday I'd love to make these things
Here are the leads of the remote control hooked up the the gun. I used a small spool of 18ga speaker wire from RadioShack for the wire, and some insulated alligator clamps from eBay.
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youre the man, this is awesome. thanks for making k less shitty
The ammunition is "standard" in electric primed. I think the only gun that uses percussion-primed ammo is the Anzio rifle, which came long after the M61 vulcan. Electric primed is just how it was designed from the ground up. The Lahti 20mm rifle uses a completely different 20mm cartridge altogether.
Here ya go. THIS FUCKING THING probably took a solid 15 hours to make, and was a giant pain in the ass.
Yes, my buddy who works at the same gun shop fractured the "scaphoid" bone in his hand from one shot. Poor guy was wearing a wrist brace for a while after that, and had to go to physical therapy. We have since leaned a less-painful way to fire it. Pic related was from the very first shot of the prototype 5.7mm pen gun. It definitely has some felt recoil... Bolt thrust is ultimately delivered to a meager 0.43 square inches of your hand. Hardest recoiling gun I have ever shot. Second place award goes to the S&W Airweight PD 340 with .357 magnums.
I buy it at gun shows when I can. Isn't exactly easy to come by. There is a website called unammo.com that now sells it, but I am yet to buy any from them. I think I had either 94 or 96 rounds total so far, and have only shot 7 so far. I'll probably bring 10 of them to NuggetFest in a few weeks. I have historically paid between $10-14 per round.
Now that it is done, it will just be hauled out to shooting parties and events (like NuggetFest) as a big obnoxious novelty.
No, the projectiles are inert. I think it is about a 1600 grain projectile. The body is solid steel, with a brass "driving band" to engage the rifling, and an aluminum nose (in lieu of a fuse) pressed in the top.
20mm is about .78-cal. It used "gain-twist rifling", to avoid torquing the gun real hard when it fires. The rifling is almost perfectly straight in front of the chamber, and picks up speed as it goes. I don't know what the final twist rate is.
>It uses two CR123 volt batteries to feed a boost converter, that makes 300V DC that is stored in a flash photo capacitor. Pressing the L+R trigger buttons dumps that current into the primer.
That's clever, very clever. I love it
There wasn't enough room to put a switch in the space where the Z-button was, the analog stock assy sits right on top of it. The flash photo caps puts out 300volts (probably a few amps, too), so I couldn't use the existing contacts and membrane without burning them up after 1 or two shots. The trigger buttons are "snap action" switches, designed to handle significant currents with minimal arcing.
Nope. CH4D reloading dies and a shellholder are like $650 for this cartridge, and a suitible CH4D press is like $1600. I will NEVER justify shooting this enough to reload.
Just 'cause. I could build any number of remote controls for it. Heck, I could even make a pic related. ...I'm actually thinking about that one in all seriousness, though I generally dislike working with wood.
I'm not a robot
You say that now. I said the same thing with my first large rifle.
If you are just neck sizing the RCBS/Hornady 50 cal press will work with a custom top plate. Can also find the old Hollywood Sr. presses for sale. They were made for 20x138b reloading.
OK, hear this. If there is snow on the ground at Nuggetfest, I will try my best to sled the bitch. I will tie the front and back of the tripod to it as best I can, and see how far it goes. Trips will it.
I have a RCBS AmmoMaster 2 press for reloading .50 BMG. I don't quite think it would work...
They work, just kind of annoying.
You need to unscrew the seating die to pull out finished rounds. It's like loading .50 on the little Lee presses.
Could also get parts like the supports and toggle made to extend the working distance. At that point probably better to rebuild a log splitter.
My own Ammomaster is a mix of parts from the I and II as well as the Auto and Piggyback I and II. Quite customizable compared to most.
cant you just use a machinist vise or something to just press the bullet into the casing with the driving band acting like a heeled bullet?
also ever think of drilling out the center of a practice round and putting a tungsten welding rod penetrator in it?
Anyway you could try like this via a separate mount?
Help me understand the construction process a little better, You use the lathe for what?. I understand you used the mill for the receiver and what not but what cutters did you use?
Ive got a mill and im looking to some gun construction
When can you replace my neighbor's windshield?
Now all you need to do is use it to defend yourself in a home invasion, shattering every bone, window and eardrum in your house afterwhich you explain to the cops why your hallway is covered in pink mist
I just can't see myself putting in the effort to reload for a gun that will probably only see 10 rounds a year once the initial novelty wears off. At least I reload a few hundred .50 BMG year, and will soon break even on the investment there. Because of the way the projectile is crimped in these cases, I don't think I could disassemble one to modify the projectile like how you suggested.
How much would that be? I'll consider it.
A lathe was used to thread the barrel, thread the receiver, and make the initial form for the breech block... The smaller items made on the lathe were the electrode, insulating bushings, and the shouldered bolts that attach the barrel clamp assembly to the pintle.
Not really feasible. Take one apart yourself if you don't believe me. If I reallyw anted to "make it work", then the analog stick would have been chopped up under the hood, and the remnants up top cemented in place and immobile. That would have been no fun.
I would be glad to hear them.
NO!! I forgot my chronograph at home that day, even though I had every intention to bring it.
Yup, all in the name of fun. I'm not even going to pretend this gun is even remotely useful or practical. As a buddy of mine put it, I just "want it to go boom, and fart out a big bullet". If I wanted a practical 20mm, then I would have spend $8,000-$18,000 on one of the three properly-set-up Anzio rifles.... of which I can't afford. Plus, there isn't as much satisfaction in just buying something.
My Gunbroker saved search this very morning just went off. The hard part is getting one with the insides in great condition, and not demilled. http://www.gunbroker.com/Auction/ViewItem.aspx?Item=536529353
Sometimes I can just flick it out with my finger, other times I need to lightly pry it out with a screwdriver.
Yess, I am expert at that.
>fantastic homemade gun
>presents it with a vertical video
You know OP, this is a fun project and all, but I'd keep working on it.
Turn it into a miniaturized artillery field gun maybe. Like this more or less: https://www.youtube.com/watch?v=abEq7bWROwA
A simple carriage with a proper windage/elevation adjustment would be possible to build, right?
This is just an idea of course, but I think it has potential.
I certainly considered this, but it just wasn't possible with the other components in there. I'll spare you the 300 word explanation of why it wouldn't work... or why I couldn't get it to work.
You can blame the girlfriend. I wasn't paying much attention to the orientation of the camera, more focused on not trying to say anything stupid for a whole minute.
Excellent, I will see you there.
>scaphoid fracture from shooting a pengun
Jesus...I broke my scaphoid playing soccer, and I know what a bitch those things are to have heal correctly. My wrist still isn't the same. Probably will never be the same again.
Don't hurt your friends like that, OP.
Except him. You can do that to him.
I know how to turn dials to move it up, down, left and right, but that is about it.
I wish. That is probably beyond my ability.
I have a connection at the moment who has 60-some rounds for sale. If I free up the money, I would like to buy it within the few months if it is available.
Nice! What the current weather like there? I live in Florida so I have no idea how seasons work.
I like it around here. I do enjoy the contrast of the seasons. It can get sweltering in the summer, bitter cold in the winter, and of course everything in-between. Some people love to piss and moan about the cold this time of year though.
Yeah, it was a poor choice of words... I was nervous for the camera, and talking quickly. The next guy got it, inert projectile.
Some other time, man. The girlfriend's place is excellent for shooting. We can get about 320 yards to shoot on out there... 400 if you shoot right next to the house (suppressed only though, because of the pets).
Posting from Turkish proxy to mitigate the fact that I am giving an information that shouldn't be given.
OP, I hope to god you made this thread via using several layers of proxies because your thread was marked as possible case terrorism under ''The Threat of Homegrown Terrorism''. Be careful OP, they are really trying to paint full-blooded Americans of certain backgrounds as terrorist, specially after newly raising militia protests.
I'll give my thread one shameless bump before bed.
No worries here, friendo. I registered to build this thing with the ATF in 2012 or 2013. If they would have had any issue with it, I would have heard about it by now. Other people own bigger and badder legal Destructive Devices anyways.
I'm not a robot