KWA KM4 SR7 Internals


KWA KM4 SR7 Internals |

(This is the second post in a series on the SR7.  To see the first post click HERE.)

Arguably, the most important part of any airsoft gun is the internals.  The internals are what allows the airsoft gun to engage other players; and be reliable and effective on the battlefield.  Different gearbox designs (Version 2, Version 3, etc.) each have their strong and weak points when it comes to their internals.

The most vulnerable part of most gearboxes are the shell.  The shell encases all of the parts inside of the gearbox.  It also absorbs the impact causes by the pounding of the piston.  This can cause the shell to crack.  Other common airsoft internal issues include, pistons stripping, teeth on the gears breaking, and trigger contacts frying.

Most of the time, if you want to solve these issues yourself, or if you want improved the performance of your AEG you have to spend money on aftermarket parts and potentially hire a tech to install your new parts.  This can add up to quite a bit of money very quickly.

KWA Performance Industries wanted to solve the common internal issues (as well as less common ones); and give airsofters excellent performance right out of the box, by designing their internals to function as flawlessly as possible.  Their answer to internal and performance issues was the 2nd Generation Extreme Gearbox and the 2nd Generation Hop Up.

(Note: I personally have not opened up my KWA’s gearbox.  I can be a bit fumble fingered at times; and the internals don’t need to be upgraded anyway.  I got the internal parts information from several good sources.  You can find an older post from the KWA forum HERE, that lists the parts and compares them to the 1st generation KWA gearbox.  HERE is a list of all the parts you can purchase for the SR7 direct from the KWA website.  Also, check out this video from AirsoftGI to get more information on the 2GX gearbox.  I will be listing the internal parts and my thoughts on how they improve the KWA SR7 below.)

Let’s take a look at the 2nd Generation Extreme Gearbox:

Completely reinforced gearbox shell- KWA reinforced the gearbox shell, inside and out, to prevent gearbox cracking caused by the relentless pounding of the piston on the front of the shell.  They also reinforced the trigger post (This is the piece that sheared off inside my JG M4 CQB during the Tech Saga), by almost doubling the size and sloping the base for more surface contact.  You won’t have to worry about any issues there.  They also reinforced around the anti-reversal latch.

9 mm Ball Bearing Metal Bushings- These ball bearing bushings reduce friction inside the gearbox resulting in a higher rate of fire and a better gearbox reliability.  They are a nice, large, 9 mm size which gives them better strength.  Although you sacrifice some reliability that regular bushings offer, due to the lower FPS (therefor less tension on the bushings from the gears rotating) of the SR7, it’s not an issue.

Metal Air Nozzle (no O-ring)- The metal construction is a nice upgrade from your standard Ploy Carbonate nozzle.  An O-ring would be nice to provide an even better air seal; but the KWA already has one of the best compression systems on the market right out of the box.

Ported Metal Cylinder- It is ported to help give the SR7 it CQB FPS.

Poly Carbonate/Brass Cylinder Head (single O-ring)- A basic cylinder head.  An CNC aluminum head ($15+) with Sorbothane padding ($5) for corrected Angle Of Engagement (AOE) with the piston, would be a way to improve this component later.

Aluminum Piston Head (non ported/single O-ring)- Its aluminum construction will last a long time.  To my knowledge it is not ball bearing.

Poly Carbonate Piston- The last tooth is heat treated metal for extra strength.  The pick up tooth (the first tooth to make contact with the gears) is fully reinforced.  The second tooth is not removed.

M100 Spring- The M100 spring is just right for the SR7.  It gives CQB FPS and less wear on the internals due to less tension from the spring.  It also appears to have variable pitch for even smoother operation.

Ball Bearing Metal Spring Guide- The ball bearings makes the compression system run smoother because the spring is able to twist on itself, reducing tension.

Heat Treated Metal Gears-  The heat treating process strengthens the gears and reduces wear on them.  More strength equals less issues.

Metal Cut Off Lever- Your standard cut off lever.

Selector Plate- Standard.  Has an electrical cut off plate to give you enhanced safety.

Trigger Switch Assembly- Silver plated for better trigger response and less resistance from the wires.  Looks like it has a heat treated spring for extra strength.  I would recommend getting a Mosfet for longer contact life, especially if you are going to use a lipo.

Metal Trigger- Standard.  Trigger pull is stiffer than you find on some AEGs.  It is closer to the real deal.

Wire Set- Silver plated for better trigger response and less resistance.

Anti Reversal Latch- Heat treated for strength.

KWA KM4 SR7 Hop Up |

Now for the 2nd Generation Hop Up:

The 2nd Generation Hop Up is a two piece unit, made out of a nice polymer.  It has the same texture as the crane stock’s polymer.  (I found it interesting that they continued the texture of the polymer to the inside of the gun.)

It is easy to adjust and my hop up setting stays in place during a game.

The best part of the 2G Hop Up is the hop up nub.  It has two points of contact (3 points when you count the bottom of the hop up bucking).  With the two points of contact from the nub you will encounter less “flyers” and better accuracy at longer ranges.  I have pitted the SR7 against field AEGs with longer barrels and higher FPS and have done just fine.  I can get the 2G Hop Up to put a 0.25g bb out to 120 feet (with the bb having an almost flat flight path till the last 10 feet) and hit a man sized target after adjusting for wind shift.  That is very good for a “CQB” AEG! 

I hope that this post has given you a solid over view of the KWA SR7’s internal make up.  The internals of the SR7 were the main reason I purchased one.  I was very impressed by the well designed and well constructed 2GX gearbox and 2G hop up.  If you are looking for a very well built gearbox and excellent internals (without needing any upgrades), be sure to check out the KWA SR7.




Bookmark the permalink.

Leave a Reply

Your email address will not be published. Required fields are marked *