Competition: A Fascist-Slaying Clandestinely-Produced SMG

[Collimatrix]

Background

 

Your country has a pest-control problem.  Fascists have invaded and are up to their usual tricks.

 

But fear not!  Like the Poles before you, you can make cheap submachine guns in secret, and build up your stockpile in preparation for Operation Remove Fascist.

 

The only problem is that these are ultra-fascists, and the only cartridge with enough Freedom to kill an ultra-fascist is .45 ACP.

 

Goals

 

Design a submachine gun that can be mass-produced in secret to help cleanse the streets of ultra-fascists.  The design must be chambered for .45 ACP, but all other design choices are up to the designer.

 

Ultra-facists, not being completely stupid, will be on the lookout for subversive activity.  Therefore your design should use common materials that are extremely common and not obviously related to weapons' manufacture.  Historically, plumbing materials and sheet metal have been popular, but again this is up to you.  Your bill of materials should be as innocuous and secure as possible, and the number of manufacturing operations that give away that you're turning these things into weapons should have minimal man-hours required, to keep the number of conspirators down to a minimum.

 

Your design priorities are, in order:

 

1)  Secrecy

2)  Cost

3)  Weapon effectiveness

 

The strange economics of the guerrilla mean that cost, as such, isn't so much a concern as secrecy.  A design that requires laborious machining of a steel billet is better than one that is made of cheap stampings if you only need one small mill and one machinist versus a large industrial stamping press, specialized dies and an assembly team of operators.

 

Consider common, innocuous, every-day mass produced consumer items for parts.  Could a door-knob be finagled into working as a sear mechanism?  Can standardized square tubing be converted into magazines?  

 

Also consider the costs involved.  Who is financing this operation?  How are the finances disguised?  How are the purchases made to look innocuous?  Does anyone need to be bribed?

 

I expect to see reasonably detailed designs with basic relevant calculations for rate of fire and weight performed.  A good solid modelling program will be helpful, but this is the sort of thing that can be (and has, many times) been done on graph paper.  Or whatever they had in Leningrad when the Nazis were attacking that passed for graph paper.

 

Resources

 

Operating system I leave to your discretion, but since I assume most of the designs will be blowback operated, I am providing links to all the resources you would need to design a functional submachine gun in .45 ACP.

 

A pressure vs. time curve for .45 ACP.  The integral of this curve (times bore area) will be momentum.

 

A pressure vs bullet travel time curve for .45 ACP.  The integral of this curve (times bore area) will be energy.

 

Chinn's The Machine Gun Chapter 4

 

Semi-empirical notes on submachine gun design

 

Contest Rules Stuff

 

I will be sponsoring this contest.  The single, indivisible award is $50, deliverable by PayPal.  If you live in some horrible country that doesn't have PayPal and you intend to enter the contest, PM me so we can figure out something ahead of time.  I am also accepting applications for judging this contest, but per the master rules judges cannot receive prizes.  All submissions must be finalized by August the 29th, 2016.

 

 

 

Alright, time to get your STEN on.

 

 

There are fascists what need killed.

[Sturgeon]

Oooh, this should be fun.

 

Also, nice Harold and Maude ref.

[Vanagandr]

AKA the Open Bolt Buildoff

Are we assuming any specific time period?

[LoooSeR]

Who will be judges? I am not very good at Dakka Dakkas.

[Collimatrix]

Who will be judges? I am not very good at Dakka Dakkas.

 

Bronezhilet so far has applied for judgeship.

 

AKA the Open Bolt Buildoff

Are we assuming any specific time period?

 

The ultra-fascists are occupying your country RIGHT NOW.  So you can use any materials or technologies whatsoever; so long as they combine to sling .451" 230 grain pieces of lead.

[Oedipus Wreckx-n-Effect]

Time for my open bolt angled-magazine Liberator pistol project to come to fruition. 

[Walter_Sobchak]

My design of a slingshot made out of PVC plumbing for chucking .45 cal shells will score super well in categories one and two, but probably not in category three.  

[Ulric]

I'm curious as to how the .45 ACP will be sourced while under ultra-fascist control, but that is just me looking for an excuse to not work with a terrible fucking cartridge that should never have been adopted in the first place. Then again, using 230 grain ball will have some advantages for certain applications that may arise in this competition.

[Toxn]

I'm curious as to how the .45 ACP will be sourced while under ultra-fascist control, but that is just me looking for an excuse to not work with a terrible fucking cartridge that should never have been adopted in the first place. Then again, using 230 grain ball will have some advantages for certain applications that may arise in this competition.

I'm actually really happy about this requirement, as I happen to have a cartridge on hand to use for measurements.

Maybe they ship it in under the noses of the fascists as agricultural equipment?

[Sturgeon]

I'm curious as to how the .45 ACP will be sourced while under ultra-fascist control, but that is just me looking for an excuse to not work with a terrible fucking cartridge that should never have been adopted in the first place. Then again, using 230 grain ball will have some advantages for certain applications that may arise in this competition.

 

More on this: http://196800revolutionsperminute.blogspot.com/2012/11/the-myth-of-45-acp.html

[Sturgeon]

Not that I think .45 ACP is a poor choice for this competition, mind you.

[Toxn]

FREEDOMISER VI SMG

Length: 33.5 cm

Width: 1.9 cm (without bolt handle)

Height: 18 cm (including 16cm magazine)

Weight: ~3.4kg unloaded

Cyclic rate: ~1200 rpm (built-up bolt)

Velocity: ~300 m/s (10cm barrel)

Magazine size: 6 rounds (16cm magazine)

Clandestinely-made SMGs serve a few roles for would-be rebels. The first is simply as a fill-in for better weaponry until such becomes available (ie: mostly to make your fighters feel better for having something better than a half-brick with which to fight). The second is as an ambush weapon for attacking high-value targets or capturing supplies. The third, of course, is to provide friendly photographers with an iconic prop for pictures of moody young fighters wearing berets and smoking cigarettes.

The Freedomiser serves all three roles, and is designed with compact size and simplicity of manufacture in mind. It is almost entirely constructed from rectangular tube, square bar stock, steel rod and thin steel plate. In terms of equipment; only an angle grinder, drill and welding rig are needed over and above simple hand tools. This allows the Freedomiser to be made in garage shops and sheds. The readily-available nature of both tools and raw materials means that it is easy to set up and conceal a Freedomiser manufacturing operation.

Design and Manufacture

In terms of design, the Freedomiser uses a single piece of rectangular tube as a frame to house the barrel and bolt, with the tube also acting as part of the magazine well. The magazine and grip/s are made from tube of the same dimensions as the frame. The barrel is a simple piece of drilled-out bar stock (using slightly different sizes of drill for the barrel and breech), while the bolt consists of a welded assembly of bar stock and a strip of steel plate (which can also be welded to the inside of the frame as a spacer).

An alternate approach to making both barrel and bolt is to set up a small casting operation and cast into open moulds. The barrel tube can then be cast with rifling – which is fairly easy to grind or cut into the rod which forms that part of the mould. The moulded parts differ slightly from the standard parts as shown. The barrel of the Freedomiser may be either welded into the frame (if made from bar stock) or bolted/pinned/riveted in place via an extension on the bottom of the barrel (if cast).

In terms of the materials for casting, both bolt and barrel may be made from brass (which is very easy to set up a casting operation for). However; for best results it would be advisable to cast at least the barrel in iron and then follow a tempering approach. The best option here would be austempering by quenching in a heated oil bath, followed by transfer to an oven to complete the tempering cycle. Small magnesium additions may also be beneficial for this approach.

Rifling of built-up barrels can be accomplished using a simple rifling jig or hand jig, with the depth being in either case very shallow. This, of course, also adds a bit to the time and complexity of manufacture. The length of a bar-stock barrel is limited by the drill bit used to make it, as well as the accuracy of the person doing the drilling. A drill press and extended bit (either bought as such or with an extension carefully welded on) can get longer barrel lengths. The barrel can also be cast in a longer format.

A cast brass bolt would be significantly heavier than a built-up one (~500g), which would help to lower the cyclic rate of the weapon and lower the chances of case head separation. In either case, greasing of cartridges would probably be helpful in making the Freedomiser function properly.

Finishing of the bolt would require drilling and fixing a charging handle to the bolt body. In the case of a built-up bolt, slots would also need to be cut for the extractor and ejector pin. The extractor, a simple shaped piece of sprung steel, would be welded, brazed or hammered into the bolt. The main spring (which can be either scrounged from somewhere or hand-wound) rests above the lower bolt extension in the built-up bolt, or inside a tube moulded or drilled into the cast bolt. Total bolt travel is about 6cm.

The magazine is a simple single-stack affair made from rectangular tube. It is designed to present the cartridges at a slight angle for feeding directly into the barrel. The follower and base would be made of metal sheet, plastic or wood, with the spring being either hand-wound or scrounged up from a suitable source. The magazine, being the same width as the frame tube, is positioned by carefully lining up the cutout in the frame. Plates welded to the frame sides position the magazine further and aid retention. On the example shown here, retention is accomplished by simple friction and the action of the operator, who uses the robust magazine as a forward grip. Retention can also be improved by addition of a sprung catch, retention spring or loop.

The trigger on the example shown here is exceedingly crude, and consists of a simple sprung catch holding the bolt open. It may, of course, be replaced by a more efficient device if needed. Sights and a stock can obviously also be added.

Operation

The Freedomiser fires from an open bolt using a fixed firing pin. The version shown has no safety or trigger guard, so in this case the weapon should only be loaded and cocked immediately prior to firing. The small magazine, primitive trigger and ferocious rate of fire means that the magazine would inevitably be emptied in one burst. A Freedomiser with a rifled barrel, heavier bolt, improved trigger, suitable sights and stock could probably achieve reasonable accuracy out to 150m or so. The short version shown here, however, would be lucky to hit anything past 25m.

Given all of the above, SOP for the Freedomiser would be to work in groups from close range – with fighters picking out individual targets beforehand and others waiting to attack after the first volley. Jamming of the weapon may be mitigated to an extent by holding the weapon sideways (ejection port down). This also gives your fighters a +1 boost to poise and style while making a ranged attack. Addition of an extended magazine and improved trigger is recommended here as well for bonus synergies.

[Khand-e]

I'm curious as to how the .45 ACP will be sourced while under ultra-fascist control, but that is just me looking for an excuse to not work with a terrible fucking cartridge that should never have been adopted in the first place. Then again, using 230 grain ball will have some advantages for certain applications that may arise in this competition.

 

Wait, you're hating on a test that Julian Hatcher approved of.

 

Do you want D.E. Watters to appear in your house and murder you with a Ruger shotgun? Because this is how you get D.E. Watters to to appear in your house and murder you with a Ruger shotgun.

[Collimatrix]

I'm curious as to how the .45 ACP will be sourced while under ultra-fascist control, but that is just me looking for an excuse to not work with a terrible fucking cartridge that should never have been adopted in the first place. Then again, using 230 grain ball will have some advantages for certain applications that may arise in this competition.

 

.45 ACP is made of such pure Freedom that when ultra-fascists tried to ban its continued manufacture and use their faces melted off.

 

I'm actually really happy about this requirement, as I happen to have a cartridge on hand to use for measurements.

Maybe they ship it in under the noses of the fascists as agricultural equipment?

 

Here are the dimensions of .45 ACP for everyone else who doesn't have a sample cartridge.

 

Not that I think .45 ACP is a poor choice for this competition, mind you.

 

I think if I allowed too much freedom in design it would be overwhelming.  So instead of design freedom, I opted for enforced Freedom.

 

I realize that .45 ACP is not a particularly good cartridge to design anything for.  However, I knew I could find good data on its dimensions and burn rate.

[Belesarius]

I'm curious as to where people take this.  I wouldn't mind being a judge as long as there was a couple of more technical minded folks around to talk about specifics.

[LoooSeR]

Just copy/paste Metro LL SMG. 

[Bronezhilet]

I'm willing to offer basic solidworks lessons. I have loads of time now so as long as you dont want a lesson at 22:00-8:30 my time I should be available.

[Sturgeon]

Hey, I'm not too proud!

[Collimatrix]

I am not planning on putting forth an entry, but I was thinking about perhaps doing some how-to posts.  Is there anyone who is on the fence about making a competition entry because they think they lack background knowledge?

 

Here are some ideas for how-tos I had:

 

-How to calculate bolt mass and rate of fire in a submachine gun

-What parts need to be metal in a submachine gun, and what other materials will suffice elsewhere

-How to design magazines for automatic weapons

-How barrels are attached to receivers in submachine guns

-How to skirt ITAR regulations by disguising advice to budding revolutionaries as a contest

-How to identify traitors and enemies of the revolution

-Secret handshakes, basic operative cell security protocols and compartmentalization

-How to defeat the Great Satan and hasten the glorious day of the return of the Hidden Imam

[Bronezhilet]

I dunno if I can help with this since I'm a judge, but all polymer production related questions can be directed at me. Includes 3D printing questions.

[Toxn]

I got bored and started coming up with higher-calibre variants of my incredibly crude design.

 

Then I realised that all the best stuff has been done already.

[Toxn]

Freedomiser is a go.

[Toxn]

I am not planning on putting forth an entry, but I was thinking about perhaps doing some how-to posts.  Is there anyone who is on the fence about making a competition entry because they think they lack background knowledge?

 

Here are some ideas for how-tos I had:

 

-How to calculate bolt mass and rate of fire in a submachine gun

-What parts need to be metal in a submachine gun, and what other materials will suffice elsewhere

-How to design magazines for automatic weapons

-How barrels are attached to receivers in submachine guns

-How to skirt ITAR regulations by disguising advice to budding revolutionaries as a contest

-How to identify traitors and enemies of the revolution

-Secret handshakes, basic operative cell security protocols and compartmentalization

-How to defeat the Great Satan and hasten the glorious day of the return of the Hidden Imam

It's a bit late for me, but magazine design is hard! For rate of fire I simply took the peak bolt velocity and travel distance, assumed that the bolt was linearly slowed to a stop and then sped back up over the distance, and did basic maths to get an average velocity.

 

Also, the bolded point is probably why there are no other entries

[Toxn]

Well fuck:

 

https://www.youtube.com/watch?v=7QL9a0HAzXw

 

https://www.youtube.com/watch?v=H2hNLsCU8eo

[Belesarius]

C'mon folks! We need more entries.

 

I was really hoping to see some creativity with this one.

 

3 D printing, Ghost guns, open bolt madness!