Home Reviews Hk21 HK21 Custom Review

HK21 Custom Review

by Arnie


for a larger image)

(stock fps may vary)
Length: 960mm
Weight: 3.2
Kg (heavy)



500 rounds

70 Round
(Standard Mag)


HK21 ‘Custom’
gears and biscuit pistons”

Well, it’s basically a G3SG1, with a
shortened A3 front end, and a PSG stock. It was made to replicate as closely
as possible Heckler and Koch’s HK21 support weapon, with a few personal touches.

the HK numbering system, this gun is a belt-fed machine gun, running 7.62×51
ammunition.  Obviously the belt-feed
is hard to achieve with an airsoft weapon, however I intend to try and solve
this partially by using a C-mag on the weapon, which would be feasible on
the real thing.

My reasons for purchase were simple: I needed a long-range gun, and my MC51
clearly wasn’t going to cut it. It was available there and then, and at a
good price.

I had
the accessories from the MC51 that would
remain compatible, and although second-hand (normally I try to stay well clear
of used rifles), it was coming from a trusted friend, and therefore I knew
the gun’s history.

This also
meant that all the hard work had already been done, the rifle was broken in,
upgraded and ready to roll. So, for the princely sum of £300, I secured myself
a ferocious piece of kit, with loads of bits thrown in (Thanks, Alex). Oh,
yeah, and running about with an LSW kinda suits a nutter like me

How can I build one? Thanks to the modular design of
the G3 series, all the parts from the other weapons fit with little work.
Hence the addition of the A3 front end, and the PSG butt is merely a bolt-on

the bipod is a little more difficult. The A3 grip is not designed for bipod
use, and so leaves no gap at the front for one. Hence you have to cut into
the foregrip, and place a collar on the barrel, from which a stud protrudes
– you can then bolt the bipod to this. Do this, and you’re pretty close to
the appearance of the real thing.

– My particular one has been shortened slightly, by removing the
metal barrel extension, and simply refitting the flash-hider flush with the
foregrip. The PSG butt has also been gutted, and an 8.4V, 1700mAh battery
pack built into it.

penny for my thoughts…
The moment I got hold of this gun, I
loved it. The firepower, the range, the rarity of the custom build. As far
as I’m concerned, it’s as good as an M60, more versatile, and a damn sight
cheaper. The shortening work has made it slightly easier to swing about, especially
for nutters like me who insist on using it in urban environments. It has made
the weapon slightly less accurate, but it’s a support weapon; since when did
accuracy matter?

Open up
on the enemy with it, and they soon go scurrying away looking for an easier
time.  Due to the upgraded motor and
high-speed gears (see problems), it sent a storm of plastic towards the unlucky
target. It also came with a nice Firefly red-dot sight (see
), and a whole stack of hicaps.

two years, the gun is showing signs of use, the usual scrapes and knocks,
but works as well as ever, with exceptional reliability (except for a small
glitch last summer). It’s had a hard life, but keeps going regardless.


At time
of purchase:

  • EG1000
  • Systema
    FTK – M90 spring, cylinder set et al
  • High
    Speed Helical Gears
  • Polycarbonate
  • KM
    outer barrel.
  • Muzzle
    velocity – 308fps

then the gears have been swopped for standard speed helicals, and the spring
replaced for an M100. After two years of use the M90 had got a little weak,
and so performance suffered. Hence the change to boost it back to previous
form, which now sees it chrono’ing at 328fps.


Lack of Power
– of the electrical sort. Due to the captive nature of the PSG battery,
I find it necessary to run an SG1 butt to allow easy changes of battery.
Conveniently, this has been modified to allow 9.6V batteries (which
I don’t run, as they would definitely compromise reliability), but 8.4’s
now slide in easily.

I’ve been running
a 3000mAh NiMH battery, but due to the recent failure of the cells in
the PSG butt, I hope to be rebuilding it with some more useful larger
cells, which can run all day without a change. Then maybe the PSG butt
can stay on all day, instead of being swapped off at lunchtime

– The first set of high speed gears in this gun were destroyed by
dodgy ammunition (I shall mention no names, but the bags of “Excel” sold to
me certainly weren’t as marked). High speed gears are less forgiving,
by their very nature, because the speed increase puts more strain upon them.
The same ammo also knocked out an AK47, which simply shredded teeth off the
piston. Mine, however, shredded the piston and the gears, proving to be:

  • Much
    more expensive
  • Harder
    to source the spares, as nobody had high speed helicals in this country

one online shopping trip to Hong Kong later, and the spares had arrived. Due
to a processing cock-up, weaker, flat gears had been sent by mistake. Being
unable to return them, they were duly fitted. They lasted about 3000 rounds,
stripping their teeth spectacularly in the middle of an intense firefight
at Sopley.
I have this time replaced them with standard speed helicals for reliability,
relying on the EG1000 motor to keep the rate of fire up.

– this is a general G3 problem, the sling pin in the stock has
a habit of falling out. Loctite and Duck tape required here…


stated above, the PSG butt is being rebuilt, and hopefully a C-mag or boxmag
will soon make an appearance for that “belt-fed” look. Apart from that, my
only plan for the future is to fit a metal body, to increase the strength,
and possibly allow slinging of the weapon. Then I just need to practice my
“Harr! Get Some! Get Some!”
from Kubrick’s Full Metal Jacket.








for Money

Hard to say, I got it cheap from a good friend. If you
were to do this yourself it could prove expensive.


complete mayhem) 5/5




HK21E page
HKPro unofficial
HK21(E)/22(E) webpage

on this review in the forums

Last modified:
Wednesday, May 9, 2001 9:37 AM
copyright 2001 ArniesAirsoft

Cookies are used improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More