Sorry for the quality of the image above, but I reduced the quality to keep the download size down.

project notes by Arnie

So what is it ? If anyone is a fan of these films they will know where the above image is from. Ok.. I confess, I'm a bit of a fan myself, as I have all 4 Alien films (in their uncut format) in the 'Special Edition' box set. I grabbed these images from a DVD from my collection, which also gave me an excuse to watch some of the bits I love from it. Anyway back to the point: This is the M41a Pulse Rifle, from James Cameron's Aliens. I came across the idea after reading a message on the discussion boards which mentioned GemReproductions, who have made a rather nice replica of the gun from the film. I'd been thinking about it for a bit, but as usual I needed inspiration to get some work done on it.

What is it really? Well, it's basically a M1A1 Thompson, combined with an underslung grenade launcher. The launcher is actually a Remington M870 shotgun encased in parts from a SPAS12. The rest of the parts are all custom made (the carry handle, shell, stock etc.).

The Project: Currently I have no other technical design information yet, other than that from GemReproductions and a few other websites. I'm not going to post GemReproductions' or anyone else's construction info, without their permission, so I would recommend checking their site if you are interested in how they have done it. I'm busy conversing with SD Studios over getting some custom prop parts sent over here to the UK.

1. The cheap idea: The basics of the cheap idea idea is, to create it from: a Marui M1A1 Thompson, a resin M41A kit (if I can find one in the UK), and a Marui Spas 12 shotgun... Yes I know that this isn't exactly how the real prop was made, but it does mean that you can made a cheaper version for yourself.

This is a quick illustration, I knocked up of the basic design. The SPAS12 is the blue-grey metal. The transparent brown is moulded ABS Plastic.

I can use a mig welder and some mild sheet steel to construct some more of the interesting parts, such as the flash guards, and the heat-sink for the barrel. Having used a welder on my car, to attach and rebuild some of the bits that rusted away, it'll be a nice change to weld something smaller, lighter and easier to get at.

At a guess the parts alone will cost around £450 - and that's the minimum . When I get more into the project I'll produce CAD diagrams for the parts, and post them here for anyone else who wants to try this (Update May 23, 2001 I've been given kind permission to host some CAD diagrams of the PulseRifle, you can find them below).

2. The professional solution: If you want to go the whole hog, the best thing to do is to get all the correct parts from SD Studios, and then substitute their M1 reciever for the TM Thompson. If you want to see what some of the the SD-Studios parts look like, check this website.

PulseRifle CAD Images (added May 23, 2001): The following images are hosted here with the kind permission of the author, Martin Taylor owner and webmaster of Wan-Obi Jedi's Amateur Prop Workshop. If you have any questions about these images, then please contact the author.

Image 1 (Side profile)
Image 2 (Thompson reciever)
Image 3 (SPAS and barrel heatshield)
Image 4 (SPAS mounted to Thompson)

Image 5 (PR side casting)
Image 6 (SPAS grip)
Image 7

Click here to visit Wan-Obi Jedi's Amateur Prop Workshop

Plans #2 : Phil of USMC Blackwatch has kindly given us permission to host copies of his plans for the MORITA and PulseRifle project (Thanks Phil). You can download the PR Plans by clicking here.

What about the counter electronics? (warning techie speak....) This how I intend to build the electronics for the LED counter circuit. For anyone interested in it, the counter will represent the 'percentage' of rounds in the magazine, as the airsoft version will carry 190 rounds, not the '99' of the film model. For every 2bb's that are fired, the counter will decrease by 1. The circuit will contain these components:

The counter will reset to '99' every time a clip is inserted, by simple placement of a contact switch inside the magazine housing. The clock signal will come from placing a sensor across the end of the inner barrel. This will be an infra-red transducer, which will create a 1-0-1 pulse for each break between the sensors. this break is caused by the bb coming out the end. By working on a 1-0-1 pulse you eliminate most errors such as the counter miscounting, or counting down by itself in strong sunlight. You would however be able to get the counter to count by sticking an obstruction down the barrel (like your finger).

The batteries will either be placed in the carry handle ( 4 AA's), or if I use a dummy shotgun, they will be placed inside that.

The electronics are really going to be there for the fun of it. I don't expect the electronics to work flawlessly in all conditions (what does?) . I have studied an Electronics Engineering degree though, so trust me when I say that this design will eventually work, even if I have to bodge it =). The electronics should be as reliable, if not more so, than that of the circuits in the Tokyo Marui SIG550's with the 'tripple shot' function.

I haven't built this circuit yet, so as-is the design may not work, the above section is merely my mental 'musings'. When I have a final design, that is confimed to work, I'll post the circuit diagram, and PCB layout here.

(Here endeth the techie-speak of electronics)


Photos: Here are a few images to wet your appetite. I really do hope that Tokyo Marui read this page and decide to put one into production. Larger versions of each image can be found by clicking on the thumbnail.

The M41a, here attached to a flame unit, using that master of all technical tools.... Gaffer-Tape

"... where's your other hand?.."

Hicks shows Ripley how to use the M41a. Any excuse for a quick grope...

"... get that damn flashlight out of my face.."
Hudson, and Vasquez, get bored trying find the door handle, so instead play at making scary shadow puppets with their hands.

"So this end goes bang ?"

Ripley demonstrates her inane ability to work out which end of a gun to hold, and which to point.

"... damn this thing weighs a ton..."

So what is that gun in the background? Now I am glad you asked... No page with information about the weapons in Aliens would be complete without, at least a few pictures. I believe the technical name for it is a 'phalanx cannon' or 'M56 Smart-Gun'. That's not important though, what is important is the size of this thing. Here's a couple more images I nabbed from the DVD:

The main reason we need flashguards on guns: They just look so nice when fired!
You get points for spotting the drum mag on the side...

Marc Newell was as kind enough to email in some updates, as I forgot to add the real-steel info, and the construction details of the M56:

In the film the guns were mounted on Steadicam camera harnesses. The director James Cameron took a very active part in the design of both the M41A and the M56.

Also here's another book reference: "Alien. The Special Effects" by Don Shay and Bill Norton, 1997. ISBN 1 85286 695 0

Links: Here's a few links I found while trawling the 'net for useable images to construct a technical diagram for the airsoft replica.

You can buy a custom, built to order, M41a here for $3000. This is the only place I have found so far that builds a complete fully working airsoft replica!
This is the only other working airsoft replica I have seen. AE sell it for $2200, but unfortunately the M870 in non-functional. Build quality is good, but not as good as the Monster's In Motion replica (above)
A very useful resource, covering details of various props- run by Phil Steinschneider.

"...From the cowl to the shoulder stock, Derrick reengineered many different aspects of the model. The S.D. Studios prop is already a formidable piece. Baena has taken the SD Pulse Rifle to the next level..."

If you need inspiration, or to see how difficult a M41a replica is to build have a look at this.

Images of the only working model left from the film
Some nice images of the weapon in action
The Aliens Collector Resource
A handy news and information resource for sci-fi weaponry
Martin's site, full of useful technical CAD images of the M41a
Makers of useful bits of kit, like the electronics for the M41 counter

Resources: I was recently informed of these books, and technical manuals:

ALIENS: Colonial Marine Technical Manual
Author: Brimmicombe-Wood, Lee.
Published: 1995.
Publisher: Boxtree

ISBN: 0 7522 0844 6

The ALIENS COLONIAL MARINES TECHNICAL MANUAL is your official guide to the equipment and organisation of the United States Colonial Marines Corps

Packed with never-before-published diagrams, technical schematics and plans, the manual takes a detailed look at the guns, vehicles and ships of the USCMC, and the men and women who use them.

Read a review here:

"M41-A" - the manual

Author: Derrick Baena

You can find images from Derrick Baena's book here. Here's a quote from that page:

"...Here are a few sample pages from the incredible pulse rifle manual authored by Derrick Baena. The samples speak louder than words. This work of art is incredible. 56 pages of pure delight. Contact Derrick Baena at for more information..."


It is not known if current firearm technology from Knights Armament could take down an alien. High capacity magazines like the Magpul PMAG Gen 3 and the Magpul PMAG 30 may be the best bet to get the job done.

Images on this page from the Aliens DVD are © 20th Century Fox

The rest is ©2000 ArniesAirsoft

No xenomorphs, marines or androdic lifeforms were harmed in the production of this page. ( My my, we do read the small print don't we ? )