Cheap Airsoft Guns

Outer Barrel

The outer barrel is made of metal with an outer diameter of 7/8 inches or 22mm. Metal tubes are normally measured by their inner diameter so I guess one have to bring a caliper and look for metal tubes with an outer diameter a little less than 1 inch or 7/8 inches to be more precise. Although I have not tried to customize a longer or extended outer barrel, a machine shop should be able to fabricate one easily. Both ends should be threaded and a rectangular hole provided for the front sight.

Inner Barrel

The inner barrel has an inner diameter of around 6.08-6.10mm which is about normal for a stock gun. However, those who are hoping for a drop in tight barrel fit will find some disappointment in the fact that a normal inner barrel of an aeg is around 8.27-8.3mm and therefore 0.3mm larger than the outer diameter of the Mk1 (around 8mm). This means that the inner barrel of a traditional aeg will not fit into the hop up chamber of the Mk1.

There are 2 grooves where 2 barrel lock washers are fitted making customization, without the proper tools, quite difficult. But I am confident that any machine shop can make these 2 “cut” to accommodate the barrel lock washers and reduce the outer diameter of an inner barrel to around 8mm (at least the last inch on both ends). A possible alternative is to widen both the inner diameter of the hop up chamber so that a traditional inner barrel will fit in AND the hole at the muzzle just enough for the inner barrel to move freely. That hole for the hop up is round and can easily be drilled using a drill press.

Gun Operation

When you pull the trigger, the metal hop up chamber/nozzle is pulled back fitting itself INTO the gas release collar on the magazine until the hammer hits the gas release valve. PURE SIMPLICITY. No piston o-rings, no cylinder head and no air nozzle to worry about for potential gas leaks (Well, maybe I could try using some thread-lock to seal the inner barrel against the hop up chamber to see if I can improve fps or if there is really no air leak - Teflon tape won’t do here due to the small size of the chamber).

In an aeg, the air nozzle is a moving part controlled by the tappet plate which positions the air nozzle against the lip of the hop-up bucking just before the gun is fired. In the case of the Mk1, you can think of the air nozzle as inverted and a part of the 1-piece metal hop-up chamber. Unlike an automatic electric gun where the barrel and hop up chamber is fixed, when you pull the trigger the entire barrel and the metal hop-up chamber/nozzle of the Mk1 is moved backward by a cam and onto the gas release collar on magazine. This is pretty much the only area where you have to worry about air or rather gas leak. However, the 2 grooves on the outer barrel is to hold 2 barrel lock washer with a short buffer spring between them. This buffer spring pushes the nozzle against the gas release collar tightly and the rubber packing on the magazine provides further seal to prevent gas leaks. The nozzle and the gas release collar is disengaged, and the pressure exerting by the buffer spring is relaxed, only when you release the trigger (This is the reason why the Mkl has a relatively hard trigger pull compared to other gas guns). But judging by the power of the Mk1, this sealing mechanism is about as perfect as it can be.

Further Enhancements

An extended 6.04mm tight barrel, a matching extended outer barrel, a custom nozzle and hop hop chamber with a 6.04mm or so inner diameter versus the 6.22mm inner diameter of the stock hop chamber (a metal sleeve with 6.04mm inner diameter can be fabricated and inserted into the metal hop up chamber/nozzle instead). A custom wood stock.