Home Projects Aliens M41a Pulse Rifle

M41a Pulse Rifle

by Arnie

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

notes by Arnie

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 Airsoft.org discussion
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.

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.).

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.

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.

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).

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

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

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

(PR side casting)
Image 6 (SPAS

Image 7


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

#2 :
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

about the counter electronics? (warning techie speak….)
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:

        • 2 – binary counters
        • 2 – binary driven
          7 segment display driver chips
        • 2 – 7 segment displays
        • 14 5k resistors
        • 2 – op-amps
        • 1 contact switch
        • 1 infrared transducer
        • 4 AA batteries
        • 2 de-bouncing circuits
          (a capacitor-resistor combination)

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)


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

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.
excuse for a quick grope…

get that damn flashlight out of my face..”
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…”

what is that gun in the background?
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:

main reason we need flashguards on guns: They just look so nice when
get points for spotting the drum mag on the side…

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

  • Gun in
    Aliens film name: M56 Smart Gun, 10mm x 28 caseless ammo
    RPM: 1200
    Sighting: Infra Red tracking unit

  • Real
    life gun:- World War 2 German 7.92mm MG42 “Spandau
    Belt fed, RPM 1200
    Still in service with Federal German Army today as the MG3 in 7.62mm NATO

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

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

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
airsoft replica!
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)
very useful resource, covering details of various props- run by Phil Steinschneider.

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.

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

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

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:

– the manual

Author: Derrick

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 76627.3052@compuserve.com
for more information…”


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

The rest
is ©2000 ArniesAirsoft

xenomorphs, marines or androdic lifeforms were harmed in the production of
this page. ( My my, we do read the small print don’t we ? )

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