TM Marui GearBox Upgrade

SG1
Gearbox Modification

“The trials and
tribulations of fitting a systema SG1 power upgrade FTK”

or

“How to make an
SG1 do a decent impression of a PSG1 sniper rifle”

Why?
Well
it’s
quite easy really. I was fitting an upgrade to my SG1, and afterwards the
gears wouldn’t turn because they touched part of the gearbox. I’ve drawn up
a quick diagram to show you what I mean. I didn’t feel much like taking photos
when I did it though, as I was feeling rather stressed…..

(Hey look… I did this
in Photoshop in 2 minutes. I was too knackered to do anything better)

So
what was going in the gearbox ?
I
was fitting a Systema UK Pro FTK, which replaces most of the gearbox, and
cylinder/piston set. It upgrades the power to 328 fps. The kit comes with
these replacement parts:

    • gear
      set
    • nozzle
    • cylinder
    • piston
    • M100
      Spring
    • metal
      bushings
    • (misc washers etc.)

 

So
what ‘s the solution ?
It’s quite simple, I took it to a friends
house, who had taken more gearboxes apart than me. With the use of a rather
sharp chisel it was possible to shave the offending lug of gearbox chassis
so that there was room for the gears to turn. You must be very careful though,
as if you slip you could easily cut through a spring or electric cable. Thankfully
all we had to remove was 3-4mm of aluminium.

‘Beware
the spring’ !

I’d recommend that when you assemble a gearbox, that you apply plenty of silicon
grease to all moving parts, and contacting surfaces. Make sure that all the
parts can move freely. With metal bushings there is very little friction to
the gear movements. Oh, and ‘beware the spring’ , when you crack the casing
to get inside, the spring will almost certainly fly out. Watch out ! – It’ll
have your eye out if you are not careful. As it is, I managed to twat Drew
with it twice, in the process of taking this box to bits.

This is the best
image I could find to describe the problem.

You can just see
the steel rectangle behind the clear plastic of the trigger mechanism.

Was
it worth it ?
It
was worth every penny, my SG1 now has an awesome range, and hurts like
hell at 30 feet =). I was daft enough to get someone to fire it at me, so
that I knew what it felt like (Arnie’s #1 Rule: don’t fire anything
at someone else that you are willing to have fired at yourself).

The rifle
has now gone from 280fps (stock) to an impressive 328fps, which is a near
to the 1 Joule limit as I want to get. In the future I may put an M90 spring
back in and put in a tighter barrel, to see how accurate I can get it, but
at the moment, it’s real fun watching people 50-60 feet away run like hell
from me.

As for reliability,
we’ll have to wait and see. I have put 12 Hi-caps through it now, and it still
purrs like a large angry tiger. I haven’t had any feed jams, yet. I
couldn’t vouch for the high-speed systema gears or FTK though. Drew went through
2 sets of gears at £60 a time. Being the sensible chaps that we are
we’re going to stick with the high power gears for the foreseeable future.

Oh, yeah
the kit was £180 from Wolf
Armouries
.

For some
decent instructions, with images, on how to take a gearbox to bits checkout
this page : Airsoft
Mechanical Disassembly Guide

 

Arnie


Except
where listed, all contents are copyright 2001ArniesAirsoft




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