Building a bullpup pump-action

www.ironwooddesigns.com makes bullpup stocks for common guns out of wood and metal. Here are some neat 10/22 stocks

Walther WA2000


Steyr AUG

While it would be uniquely yours and one of a kind. I think you're money, and more importantly time could be better spent elsewhere. That Bushmaster outline you have there would be a good start if you really wanted a bullpup rifle that was halfway affordable. Then you could take your time, which is probably more valuable, and spend it at the range.

I know a little bit about this. I've built a prototype bullpup FAL kit. (now postponed while I work on other projects). I'm assuming you are talking about building this up for future actual production, as opposed to just a one of a kind for fun, so I'm going to address the go to production aspect.

First, be prepared to spend money.

Build your prototype out of steel. It will weigh a ton, but it is the easiest material to work with. Cheaper too. When you screw up with aluminum, it is a lot more frustrating. Plastic is great and all, but not the easiest or cheapest thing to work with unless you have a real facility for doing plastics work. There are machinable plastic blocks, but it isn't cheap. For your proto, I really say stick with sheet steel. Production models can always change.

If you aren't a machinest, you need to become friends with one. Machine time isn't cheap. You are going to machine many small parts, or utilize parts from other existing guns. With a bullpup you need to come up with a new trigger mechanism, and all the parts related to it, action bar, manual safety, that kind of thing. Those little parts are not cheap.

Have somebody other than yourself look over your blueprints before you start cutting anything up. Especially somebody who does design work for a living. It is very easy to overlook small things when you are in the design phase.

Once you get the prototype up and running, have other shooters play with it. You will be surprised some of the great common sense ideas they will present you with.

Use as many existing parts as possible. Building new parts is expensive.

On your trigger bar, (and I learned this through much trial and error) design it so that you pull the bar forward to drop the hammer instead of pushing the bar back. That is probably one of the main reasons that bullpups are considered to have bad triggers. When you push something that long, it will flex,when you pull it, no flex. See?

Protect your trigger bar. I saw another bullpup prototype that had an exposed trigger bar. That is just plain stupid.

On a 7600, the action isn't particularly robust, and it will be sitting directly under your cheek. (not the most comfortable cheek weld either). Take a hard look at how you are going to cover the receiver to protect the shooter's face in case of a catastrophic failure.

Good luck.

I would suggest using as many existing parts as possible to cut down your R&D costs. It'll cost a bit less if, for example, you can salvage 50% of your internals with existing market parts from various firearms rather than starting 100% from scratch. The less you need to design, the lower your costs can be.

The Bushmaster M17S uses a large extruded aluminum shield to cover the internals. It is carbine in length but it actually has a 21" barrel. Extruded parts can be much cheaper than machined parts depending on quantity. I believe owners of the M17S are pretty happy with it's accuracy overall. If you use plastics, you'd likely need some type of fiber-reinforced nylon. I believe Glock firearms and many others use a derivative of Nylon 6/6.

It is in my non-professional opinion that the best and easiest thing to do first is build the entire model on a computer. Something might look good drawn on a piece of 2D paper, but it might not all work together in unison in 3D space. I've had that happen before. Building the entire thing on a computer allows you to make sure that all parts will fit together the way you envision it. It allows you to make small changes without actually spending money on revising an existing proto part. Its cheaper to iron out wrinkles with electrons on a computer monitor than with bars of metal stock.

One note is that many bullpups usually have squishy triggers due to the way the linkages are set up. If possible, I would like it if someone designed a better bullpup trigger. Correia suggested an alternative, and if you stiffen up the parts overall, it should improve drastically.

I like the idea as I have a Bushmaster M17S and some time back I saw anawesome looking .308 Bullpup Sniper Weapon on the cover of Guns and Ammunition for Law Enforcement

So the idea is not that unusual, but you need to remeber that your gun has to remain a certain length so as to not violate the 1934 NFA (I believe its 26" overall, someone back me up here...). Also, you will have to figure out how to make the trigger work. My understanding is that this is the tuoughest part of building a bullpup (and it is the biggest drawback to the M17S...it's trigger is very mushy).

Otherwise I hope you get it worked out and share lots of pics and info for us LAZY ones.

seen the neostead?

http://world.guns.ru/shotgun/sh08-e.htm

starship trooper anyone?

This is a german site:
http://www.bullpup.de
which has many links, pictures, and technical data, so I guess you should find some ideas.
Mossberg sold the 500 Pump gun as a bullpup, which you might have a look at (try finding a exploded diagram)

One thing to consider is the mass of the trigger transfer bar. If it is heavy enough knocking the gun in one direction can 'pull' the trigger.

Questions:

What's that widget on the front of the High Standard's carry handle?
Where does the term "bullpup" come from to describe that layout of firearm?

~Slam_Fire

Thats a 2 cell flashlight. The 10-B moved the light to the left side and had a tall front sight.

Here's some pics of the bullpup stock bucks that I made from 1" MDF. http://www.perfectunion.com/forums/index.php?showtopic=15151&st=15 I had to link this thread because the pics arn't on this laptop.

Edited to remove link, because of virus warning.

get a copy of solidworks and learn how to use it. it'll save you a lot of grief when prototyping.

Bigfoot, clicking that link is dangerous. There's a trojan planter on the other side.

The Perfect Union forum? I wouln't know a Trojan Horse from a mule deer so I'll take your word for it.

The point for my link (besides showing off my stock carvings) was to detail how I did them. I made my drawings and transfered the outlines to 1" MDF twice, then screwed the two pieces together and started carving. It was very easy to carve with a D/A sander and a Dremel tool, but was still stiff enough for the thin trigger guard areas and scope rails. It's great modeling material.

Andrew Wyatt, I hope Solidworks is more intuitive to use than the Auto Cad that I used in college.

I'm going to lay up the bucks in glass for the molds, and then lay up the waxed molds for the stock halves. That way I can lay up the trigger mounting points, bedding, etc. Depending on the rifle used I'll either bond the shells together permenantly or lay in fastener points like the Muzzelite stocks. I've worked with glass before it's very simple but it sucks. Really messy, smelly, and contacting the tinyist bit of glass (especially sanding) will itch for days. I found some info by using Google.

About the MDF though, after I'd made a couple I could cut out and shape a buck in about an hour. So if you screw one up it's no sweat, either patch it with wood putty or make another one.

Gratuatis links http://world.guns.ru/shotgun/SH26-E.HTM
Mossberg 500 pump bullpup http://www.csmetall-werkes.com/images/Moss bullpup.jpg
Muzzelite used to make a pump shotgun version IIRC.

Yup. That's why I used two pieces of MDF to make the bucks. I'll split em apart and lay the molds one half at a time. And the same with the final product so I can do the inner detail and make interior changes easily. All the bedding will be on one side, with the other side adding support. If the stock was split down the middle like the bucks are right now good bedding would be a nightmare.

When you make the molds though, lay them up real thick so they don't warp. It's a good idea also to brace them with wood or metal, just bond the support to the mold while your laying it up so the mold sets up without warping.

Solidworks is significantly more intuitive than Autocad. it's all GUI and dead simple.