The Tutorials Section:
Pulse Rifle Barrel Vents
Last updated: December, 6 2002 3:50 PM (CST)

How to Install a Metal Pulse Rifle Barrel Vent
on the Tokyo Marui M1A1 Thompson Airsoft Gun.

Please Note: Many of the following images and instructions were created by
Gary Weaver II. Gary stopped making pulse rifles, and parts over a year ago,
but his suggestions and directions are very useful and sound. I've included
suggestions as well from my own experiences in building AIRSOFT pulse rifles.
These instructions can of course be modified to work with Thompson SMG parts
other than those made by Tokyo Marui, however, this tutorial is aimed
at those who are specifically making a firing airsoft Pulse Rifle.

Although I have used these instructions in making my own props, I accept
NO RESPONSIBILITY if you ruin your own airsoft gun or other parts
using these instructions. They worked for me, they might not work for you.
These instructions are worth exactly what you paid for them.

Dean O Does periodic runs of movie authentic metal "Hero" barrel vents and
stock sets. They are very nice quality and quite durable. If possible I highly
suggest buying a set.
To do this modification will require tools. I suggest...

You will also need the following items. (1) Tokyo Marui M1A1 Thompson Airsoft Gun.
You need the M1A1 style, the cheaper, plastic, M1928 versions with the top
mounted charging bolt handle will not work for this mod.

You will need a metal barrel vent set. (duh!)

You will need to READ the manual that came with your Thompson.

I'm assuming you have some experience working on airsoft guns, so I won't
get into the nuts and bolts of gun disassembly.

Part 4: The Barrel Vent

You'll need to remove the outer barrel from the upper receiver of the Thompson.
Remove the solid stock and the rear sights from the upper receiver.
Push the locking button on the lower rear of the receiver up, and seperate the
upper and lower receivers. Don't lose the button and spring, you'll need them
to reassemble the gun.

Receiver, locking button and parts that will become the locking stock release button. Image By GWII.
In the stock is a silver piece that a bolt locked into. Remove these extra
parts and put them in a safe place. You 'll need them later.
You'll need to remove the outer barrel from the upper receiver of the Thompson.

Outer barrel. Image By GWII.

Mark the barrel where you'll need to cut it. The "L" shaped space that remains will
butt up against the flat back of the barrel vent.

Image By GWII.

Image By GWII.

Line up the 2 parts. See how nicely they match up now?

Image By GWII.

Line up the 2 parts. Butt the flat bottom of the barrel vents against the original
foregrip locking hole. You may need to slightly file the section where the barrel
vents will sit, to allow them to sit more level as the tounge that projects is slightly
beveled. Tape the 2 parts togeather when properly situated and drill a hole that will
be used to bolt or pop rivit the 2 parts togeather. You'll need to drill through the barrel
vent and also into the metal bracket underneath.

Parts taped for drilling of underside. Image By GWII.

After drilling, connect the 2 parts with either a bolt or pop rivit. On my first gun
I used a bolt. On my last gun I used an aluminum pop rivit. If you decide to use rivits,
be sure to put a couple washers on the inside of the vent, insert the rivit and pop
the parts togeather.

You may or may not want to Wait to actually connect the 2 parts permanently until you have
a new outer barrel.

For the outer barrel I used a piece of "Black Pipe." I bought this at my local Ace Hardware.
It's reasonably cheap, thick, strong and heavy. The inner barrel of the Thompson is slightly
over 6mm in diameter. Do NOT buy galvanized pipe. Go with the "Black" pipe. The process
they use to coat galvanized pipe actually makes the inside diameter too small! I learned this the
hard way by wrecking an airsoft gun barrel. The proper size black pipe will just slide over the
inner barrel slick as can be.

I cut my pipe about 13" in length. I did have to shorten it a little bit more, but because you have
that hacksaw it shouldn't be a problem. My barrel sitcks out similar to the screen Used "Hero"
gun. Some people like theirs shorter, make your own decision. You may need to crown the inside of
the new outer barrel pipe and remove any flashing caused by cutting the pipe.
This is normal.

Dean O barrel Vent. Image By Rook.

Dean O barrel vent. Image By Rook.

The long length of the new outer barrel recesses back into the upper receiver slightly.
Reinstall the barrel vent and old outer barrel on the Thompson upper receiver.
Slide the Black Pipe outer barrel over the copper airsoft inner barrel. When the barrel
is slid back as far as it can go, you'll need to add a piece of tape to hold it in place.

Get out that drill kids, now you need to drill a SMALL hole in the top of the OLD
outer barrel. When you penetrate the inside of the outer barrel, you'll nick the
outside of the new Black Pipe outer barrel. Remove the Black pipe and finish drilling
the hole in the black pipe. Now you have a hole through both outer barrels. At this point you'll
also need a SMALL, short length screw. The screw should be wide enough to fit snug
in the outer hole, but short enough that it won't dig into the copper airsoft barrel.
Screw it in place and your new outer barrel is locked in securely!

Make sure the locking screw is placed far enough back so it is hidden by the pulse rifle shroud.
Some people have even placed this screw on the side of the original outer barrel.
I always place mine on top and haven't experienced any problems from doing so.

Dean O barrel vent. Image By Rook.

GWII barrel vent, Image By Rook.

Looking at the image you may notice that the black pipe outer barrel drops slightly
at the rear of the barrel vent. This is common because of the way it straddles the
copper airsoft barrel. The front of the barrel vent also dips slightly. This is
common as well, and is not as noticeable when the grenade launcher is in place.

You could also place a couple extra spacers (small metal washers) at the rear of the
barrel vent to level it out some. It seems to help a little.
Back to the Tutorials Main Page.
Tutorial: How to install disassemble your M1A1 Thompson Airsoft Gun. Tutorial: How to rewire or modify the wiring on  your M1A1 Thompson Airsoft Gun.
Tutorial: How to install a metal barrel on your M41 Pulse Rifle. Tutorial: How to install a metal stock on your M41 Pulse Rifle.
Tutorial: How to build an M41 Pulse Rifle. COMING SOON!!
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