KJ Works CO2 1911 Gas Fix
Recently I chose to get into airsoft (July 2017) and one of the first things to buy is usually a sidearm. I chose to go for the KJ Works 1911 which from what I read had a great write up. I used to have a Smith and Wesson CO2 pistol that shot at 10J of energy and averaged around 70 shots, I figured a bb gun should equal this, it didn't. The gun would only shoot around 20 shots before the CO2 was empty, I could even see ice coming out the end of a gun, either it needed a hell of a lot of gas to push the slide back or it was leaking. I later found a major problem with these guns was that the blow-back cylinder would crack on the earlier generations, mine was a newer generation which has a stronger cylinder, still plastic.
I chose to investigate by taking the gun apart, I was really surprised to find that the gun broke down very similar to the real thing. I will add here that this page is not a guide, it is only what I did to fix my issue, so you can follow it, just don't hold me responsible.
The first step was to ensure that there was no magazine present, the slide then had to be removed by pulling it back and removing the slide pin.
The slide pin removed.
The slide then came off the front of the gun, the hammer released.
The slide return spring was then removed, it was first pulled off a pin connected to the barrel, the remaining spring along with a collet then slid out from the slide.
The cylinder assembly was then removed by unscrewing a 2.5mm allen bolt from the rear of the slide.
The cylinder assembly, don't loose the spring.
The piston held in place with a philips, the cylinder literally fell off the piston which meant there was no interference and therefore no seal. This is of course the reason why the gun is so bad on gas, it is literally blowing by the seal.
The bore of the cylinder measured 13.7mm.
The diameter of the piston seal also measured 13.7mm.
The seal was removed from the piston so I could measure the original part.
A sketch of the original part.
The part in 3D.
The new part I shall make, the only difference is the diameter of the section where the seal will sit, I increased it from 7.45 to 7.9mm.
I decided to make the piston from plastic via 3D printing since I wanted to finish the project quickly and making one from metal was simply just over-kill. I modified the design to suit 3D printing, the large fillet was placed to remove the over hang.
The design was placed in Cura which generates the code for the printer, my material of choice was PETG because simply it's excellent, it fuses together really well and has some flexibility.
The part printed pretty much perfect, the outer line is to get the nozzle extruding perfect before the printer prints the actual part.
I fit the seal and the cylinder fit perfect.
The gun was assembled and test fired, no visible CO2 or ice.
In a few days I will perform a test to see how many shots the gun will now take, it's previous record was 19 shots. If anyone reading this page wants a piston making then contact me, I can either make them in plastic (3D printed), plastic (machined) or aluminium (machined).
Please take a look at my other projects, there's more airsoft or other electromechanical.
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