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If you caught the last installment of my A&K M60VN Review, you no doubt saw the underwhelming footage of this general purpose machine gun's performance at 30 yards.  As I stated in that blog entry, I had a sneaking suspicion that there was an internal issue with the hop-up.  Turns out, I was right.  Somebody at the A&K machine shop didn't quite have their settings dialed in on the CNC machine.  I think my photos pretty much explain what happened.  See below.

First, to get to the hop-up, you must remove the outer barrel on the gun using the barrel release lever seen just above the hand guard. 

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A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
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Push the bolt in and rotate the barrel release lever 90 degrees
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
Go no further than 90 degrees, barrel won't release otherwise
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Get the rest of my expoloratory Airsoft gun surgery on the A&K M60VN Machine Gun after the jump...
Make sure to unplug the connectors for the ROF Control MOSFET Unit before pulling the barrel assembly all the way out. 
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A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Since I had no idea what I was dealing with, I decided to take the whole barrel assembly down so that I could at least get a full understanding of how it worked and was put together.  Therefore, two allen/hex screws must be removed, top and bottom of outer barrel.
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
The inner barrel and hop-up assembly have now been removed from the A&K M60VN outer barrel.
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Looking at the assembly from the opposite angle, you can see the spring which keeps the hop-up seated firmly against the gearbox when the M60VN is fully assembled.  Be sure not to lose this spring as it is not secured as it sits here in the photo. 
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A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
To get the hop-up dial off, in order to access the piece that presses down on the rubber bucking, remove the o-ring seen in the picture below.  Use a precision tip (nothing razor sharp that might cut the o-ring though) and insert into the dial's notch to pry the o-ring out of its groove. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Part of this issue is a soft nub.  Too soft, in this case. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
However, the main culprit is some shoddy machine work on the hop-up assembly (below).  See inside that hole?  We shouldn't be seeing what we're seeing there with those rough edges, which were preventing the nub from being pressed down onto the rubber bucking.  This is probably the major reason why I had to arc my shots in that performance test video at 30 yards, which is farther than most performance reviews you'll see out there, but isn't really that far in the whole scheme of actual skirmishing. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
DREMEL 4000 in a Drill Press Kit FTW
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Ahhhhhhhhh.....That's the sound of my satisfaction.
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
I checked the clear rubber nub with the inner barrel and hop-up bucking installed once I Dremeled out that blockage in the hop-up chamber, but it still wasn't pressing the bucking down far enough into the barrel as I would have liked and I suspected that it was due to the softness of the bub's rubber material.  So I then tried the a harder rubber nub that I had in my spare parts drawer (THIS IS SUCH A CRUCIAL DRAWER TO HAVE).  It's instances like these which justify the fact that I rarely through small Airsoft parts or even scraps of various materials away in case I might that stuff for a future project like this.  Anyway, as you can see in the photo, the black nub, while of a harder consistency than the clear nub, is shorter than the clear nub and therefore the net effect on the hop-up bucking was the same as the clear.  Not enough.  So I determined, as per usual, Harder and Longer is better.  So the easiest thing I found was to actually use a PolarStar Concave Spacer, but not in the traditional way that it was designed to be used.  It is not only made out of some type of hard plastic, but also is of the desired length I needed. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Voila. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
That should be plenty of engagement to get the hop I desire.  I know it's out of order, but this is the "BEFORE SHOT," and is pretty much what the inside of the inner barrel looked like with the old nub, even fully engaged.  Pretty much zero hop because of the blockage. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
While I had the inner barrel and hop-up apart, I decided to drag a little paper towel through the barrel to see what else might be in there besides oxygen.  I found dirt wanted to hang out as well, however, my inner barrels are racist against dirt and therefore don't allow its kind to cohabitate inside my barrels.  That was dumb, I know. 
A&K M60VN Review, A&K M60VN Hop-Up Issues, Airsoft Machine Gun, Medium Machine Gun, General Purpose Machine Gun, Airsoft Gun Reviews, Pyramyd Airsoft Blog, Tom Harris Media, Tominator
A&K M60VN Review - Fixing the hop-up
Tom Harris for the Pyramyd Airsoft Blog
Anyway, I've put quite a few rounds through this thing, trying to figure out what the dealio was before I took it apart, and I think I was using some dirty BBs at the time.  Anyway, CLEAN YOUR BARRELS every now and again.  That's all for today. While you're waiting for the Tominator's next installment of the Pyramyd Airsoft Blog, please help him continue to pursue his passion and provide you with a continual stream of Airsoft gun reviews, industry news and other stuff from the 6mm world by nominating and then voting for the Pyramyd Airsoft Blog in the 2nd Annual Players' Choice Awards, hosted by PopularAirsoft.com.  The links are below.
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