[Basic-Wedge]

I just received my new WE G39K yesterday, and I really like what I've seen of it thus far. After many hours familiarizing myself with the rifle, installing upgrade parts, and firing it in an effort to tune its output, these are some of my initial findings:


Straight out of the box, this rifle is a monster!

In unmodified form, it launched .25 BBs at 425 fps, using Coleman brand propane, at 20°C. A follow up test, later in the day, using duster gas, saw .25 BBs averaging 295 fps, at 23°C. Back to propane, and with the RA-Tech NPAS valve now installed, velocities averaging 394 fps were observed under 27°C temperatures.

So far, all velocities achieved with propane are far in excess of our local field limits. To tame down to acceptable velocity, the rifle will have to output no more than 350 fps with .25 BBs (about equivalent to 400 fps with .20 BBs). I'd be happier with even more leeway, say about 325 fps.

The NPAS valve has velocities heading downward, but I'm going to have to develop a better comprehension of how it works in conjunction with the rifle's nozzle before I can properly tune the system. I don't know if the valve should be mostly opened or almost closed, or how much I should trim off the tabs on the G39's piston. It all seems a bit muddled at this point.


I've read that many users experience slight over-hop, even with the hop-up unit set to its lowest setting. I experienced that too, but solved the issue by removing the stock hop-up nub, and replacing it with an “H” shaped SCS, or “Shredder Concave Spacer”. The stock nub is noticeably thicker than any nub I've previously encountered – I'd say it's simply too thick for this application. Now, with the Shredder, I'm getting a beautiful, flat trajectory over huge distance.

While I had the hop-up system disassembled, I took the opportunity to apply a thin wrap of Teflon tape around the hop-up rubber and down the barrel about 2cm. I've noticed some users report this helps stabilize the inner barrel. In my case, I did it with the hope of forming a more airtight seal between the hop-up rubber and the barrel. In any event, it doesn't hurt anything, and it may even help.


A comment I've read often is that the barrel nut is on so tight, extraordinary means must be employed to remove it. On my rifle, I used a section of 1/8th inch flat steel as a makeshift wrench, inserted it into one of the slots, then carefully loosened the barrel nut. I would not advise using a flat blade screwdriver for this, as the blade will surely be too thin and the tapering will work against you. Using a flat bar of steel seems much safer.


Once I'd gotten the inner barrel out of the rifle, I thought it might be a good idea to run some cleaning patches through it. I'm glad I did, because it was extremely filthy. I used a dozen patches before I had it cleaned, and some of the first patches picked up specks of brass and other flecks of metal. The inside of the outer barrel also needed cleaning, as there was quite a bit of debris in there too. The stock inner barrel is a stout 34cm long 6.03mm tight bore, made of thick brass. RA-Tech makes a replacement 6.01 tight bore, but with getting velocities under control being such a daunting issue, I don't see myself ever wanting a barrel which will, again, boost BB velocities.


A popular modification recommended for the WE G39 is to replace part #125, listed as an M3x3 screw (a 3mm allen head screw, 3mm long) with a similar fastener that's 5mm long. Early production models may have benefitted from this mod, but my rifle came from the factory with an M3x5 already installed.


There are several parts changes I've made that I'd like to recommend to other G39K owners:

I replaced the WE aluminum flash hider with a Classic Army G36K flash hider made of steel. The CA unit is noticeably heavier, and I like the improved balance that extra weight provides.

I also replaced the original charging handle, made of reinforced polymer, with a CNC'd aluminum unit from NeBula. The two parts look absolutely identical, but the aluminum handle should stand up longer to repeated use. The NeBula came from Tokyo Model Company in Hong Kong and sells for $28 USD. To swap out the handle, all it took was the removal of a single pin.

I also installed a WE IdZ stock and top rail. The stock folds, same as the original skeleton stock, but is adjustable for pull, and has a cheek rest with three settings. The top rail is a simplified design, featuring folding back-up sights, which snap crisply up or down. I've taken advantage of the increased amount of available rail space, and mounted a clone 3.4x Elcan scope at the back end. I'm hopeful this robust unit will handle the rifle's fairly stiff recoil.


The only portion of the rifle I haven't tackled in depth is the trigger group. For now, I intend to check the entire assembly for loose fasteners, then lubricate it with Break-Free CLP, the synthetic lubricant of choice for all my firearms going back many, many years.

On the exterior of the bolt carrier group I've been happy using Phil Waterproof Grease, but I'm still searching for the right lubricant for the inner parts of the BCG. None of my usual choices have given me the smoothness of function I experienced with the original factory applied lubricant.


That's all I have to report at this stage. My G39K shows plenty of promise. I've made excellent headway on it so far, but I have to focus now on getting the velocity under control, so I can use this in local games.