TM Marui GearBox Upgrade

SG1 Gearbox Modification

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

"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:

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