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Glock 18C High Power Kit Installation and Review

Got one of these? Want to keep it looking just like this? Then you should probably navigate away from this page.

Otherwise, if you’re truly determined – then click onwards for the upgrade kit guide and review.

Review and info about the High Power Upgrade Kit for the G18C

Everything you have read or heard about the hammer spring installation on theG18C GBB is true. It’s a horror show. But if you are brave or foolish and still want to attempt it, or you have already attempted it and are desperate for clues on how to reassemble your gun, then maybe this page can help.

WARNINGS: Like a puzzle, there is only ONE way to put the parts together to get a working gun. Unlike a puzzle, the parts can fit together in many ways.

Parts WILL try to escape. I will attempt to warn you of them in this guide. If you lose ANY part you are fucked.

This is NOT a complete step-by-step guide. The information here should help you but DOES NOT DO ALL THE THINKING FOR YOU.

Still here? OK then.

Contents of the High Power Upgrade Kit

First, we have the 150% hammer spring. This is the worst to install.

It’s pictured here next to the original hammer spring. The high power on the left, the original on the right.

Notice the high power one (mine is a “Hurricane” brand upgrade kit) is shorter. The high power spring mashes the gas release valve on the magazine faster and harder for more gas release.

Next is the metal recoil rod and strengthened spring. This is super easy to install – just replace the original.

The original plastic one is shown on the top, the upgraded one is on the bottom.

It gives a crisp, hard action to the gun. The action’s otherwise a bit mooshy with a metal slide and original recoil rod & spring.
Finally, we see a Hurricane high-flow valve next to a homemade highflow valve made out of an original valve with two tines cut out. You can click the image for a closer look.

The hacked original valve is on the top; the hiflow valve from the kit is on the bottom. As you can see the real hiflow valve is beefier looking and is of a slightly different construction.

To install the valve, you need to unscrew the original from the mag and replace it with the new one. This can be a bit tricky. An expensive tool is available to make this easy, but you can make do with some ingenuity if you have a well-stocked tool bench. Think of the tool required as a two-tined “forked” flathead screwdriver.


The only piece that isn’t easily installed is the upgraded hammer spring (though you do need a special tool to do the magazine hiflow valve – or some ingenuity). Without the new hammer spring, the gun seems to work well – but to get the highest performance, you need to install the stronger hammer spring.


I think it is, but only if you either have a metal slide and dislike the mushiness of your action, or if you need the increased muzzle velocity. There is a definate difference, at least to me. Your mileage may vary.

Note, however, that although the gun now shoots hard and fast – I can no longer fire an entire magazine in full auto without noticing a definate slowdown near the end. Prior to all upgrades, I could fire the whole magazine with no extreme cooldown effect.

The cooldown is extremely noticeable if you are firing a cold magazine. If the magazine is warm, you can still get about 1.5 mags worth of shots if firing in semi-auto or bursts of full-auto. An entire magazine of full-auto will result in a slowdown near the end of the magazine.


First of all, remove the G18C’s slide assembly. In other words, field strip it.

Some details about how to field strip the G18C can be found in my review and tech info on this gun, but if you don’t know enough to field strip the gun without help you should probably not be attempting these upgrades!


You will need to REMOVE two retaining pins. The best way to do this is with a thin and strong rod smaller than the retaining pin; a bamboo chopstick tip (may need to cut down), a plastic rod, etc. Using a metal rod to push the pin through will scratch up the end of the retaining rod.

Place your chosen implement against the retaining pin with the gun flat on a hard surface. Tap away with a hammer or rubber mallet until the retaining pin gives way.

Remove the larger of the pins just above the trigger (part #59) as well as the pin all the back on the handle straight behind from the trigger (part #86).

Removing Part #86


Disconnect part #64 (a little spring holding down the trigger bar going to the hammer assembly) from the metal trigger bar (part #92). Leave it connected to the rest of the gun. Be gentle.


Begin lifting out the hammer assembly, but before you go too far…

Look at this picture, which gives a good look at the hammer assembly. The bar leading out to the left is the trigger bar. The spring right in the center of the image WILL pop out the instant it has a chance.

As soon as you can see it, remove it and set it aside – it’s part #82. Remove also part #81 (the part it’s with). We won’t need them again until we re-assemble; they are almost the last two pieces we will be re-assembling. Again, watch that spring when taking it out AND when putting it back in.

Lose it and you’re screwed. That goes for ANY piece. I won’t bother mentioning this point again since you’re either aware of it by now, or careless. Either way, repeating the warnings won’t help you more.

After lifting out the hammer assembly, you can lift out the trigger assembly (not pictured). It should lift pretty much straight up and out (at a bit of an angle) now that it isn’t anchored in by part #64 or the retaining pin.

Here are some images showing a look inside the hammer assembly. Click for high-res versions. You can use these as a guide if you get stuck.

Note that picture #3 shows placement of the flat end of the hammer spring (look at the upper-right inside the hammer assembly). In other words, where it should be to have tension. There are many places where the spring’s flat end could fit, but this is the only correct spot. It is NOT against part #267. It is on a flat ledge inside the frame of the hammer assembly. This is a total pain to reassemble.


Remove the retaining pin (part #76 I think – mine has a “knob” on the end but the schematic doesn’t show that).

Take it out all the way. This parts holds together parts #263, 264, 265, and 78. Part #78 is the one that actually pops out to hit the gas valve on the magazine.

You can lift out part #265 and the hammer and the hammer spring. Leave the rest. Part #78 will “dangle” somewhat inside the hammer assembly. The trigger rod (part #92) loop is looped around the side of the hammer.

Here you can see inside the hammer assembly with the aforementioned parts removed.

Click for a high-res version.

In this picture part #78 is stuck up against part #267 (left).

You know, looking back on it now this thing is as complicated as a cukoo clock.


Take the original hammer spring off the hammer (part #263).

Replace it with the higher power spring. Here is a picture of how they fit together.

Click for a larger version.


(Optionally, you may take the rest of the assembly apart at your own risk. It may make reassembly easier.)

This is the tough part.

There is no step by step. You need to re-install the hammer and new spring into the assembly, then re-install part #265, then hold everything in place until you get the retaining pin back in.


  • Remember where the end of the new hammer spring is supposed to rest. Inside the ledge of the frame. It will want to go ANYWHERE else.
  • Ensure the slotted end of the gas release hammer (part #78) goes into the slot in the middle of the hammer (part #263). It (part #78) will want to get pushed down by the hammer (as you insert the hammer from the top) and get stuck vertically inside the frame. The blunt non-slotted end needs to be pointing out of the slot for it – located in front of the frame.
  • Part #265 should be inserted as well. Get it the right way around and make sure it sticks between the frame and part #267 properly. Review the schematic and images.
  • Don’t forget that part #92 (the trigger bar) loops around the end of the hammer BEFORE the retaining pin is put in.
  • Don’t forget to replace the first two parts we removed (#81 and small spring #82) before sliding the hammer assembly back into the gun. The spring will want to escape with the slightest chance.


When you’re done, you can put the trigger assembly back into the gun, re-attach the little spring (#64) to the trigger bar (#92), then push the hammer assembly back into the gun. Take this opportunity to replace any lube you removed from the assembly.

Then, replace the retaining pins that we took out at the beginning. Tap them back in with a small hammer or mallet.


If re-assembled correctly, you should be able to:

  1. Push the hammer down to cock it.
  2. Push down Part #81.
  3. Push the tip of Part #265 forward and hear/feel a small “click”.
  4. Pull the trigger (which pushes Part #266).

Step #4 makes the hammer fall and pushes out the gas release hammer (Part #78).


Cock the hammer (steps 1-3 above) and put the slide back on the gun. Then test by pulling the trigger. The hammer should fall.

Try dry-firing the gun with an empty magazine inserted. If all seems well, then fire with a gas-charged magazine inserted. Then try with a live magazine and BBs. Try both semi-auto and full-auto.


Bummer. Review this info and try again. Or send it to someone who can install/fix it for you. Your favorite retailer should also have an install/repair service. Good luck with that.

G18C PARTS SCHEMATIC – Click for larger version