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Servicing your HW100
This is a collection of great tried & tested tips, tricks and advice from our Service Engineers & Customers. This section will keep growing, so keep an eye on it!
It can be quite daunting the first time you attempt to service the HW100 yourself. Some of the most common mistakes people make are overtightening the gun when putting it back together, using the wrong tools or o-rings/seals or scratching the gun whilst trying to remove old orings. PLEASE be careful - the HW100 is a precision instrument. If you don't have the right tools or the confidence to attempt it yourself, please contact us or your local Gunsmith to do it for you.
Learn More
One of our customers, Martin Healy has made a series of 3 You Tube videos on how to service your HW100. MANY of our customers have found them helpful...
HW110 - ANTI TAMPER REMOVAL
There are quite a lot of "armchair experts" giving advice on how to remove the anti tamper from your HW110. PLEASE be very very careful when you attempt this yourself. The HW110 is not like the HW100 which can be taken apart with conventional tools - the HW110 needs custom/specialist tools to get inside the hammer assembly to remove the anti tamper or replace the hammer spring. SOME HW110's, if you are really lucky, the anti tamper just falls out (it has been known to fall out and get stuck elsewhere inside the gun!). Usually, it is locked into place.
If you have watched a video or been told to remove the anti tamper using heat - please note, if you apply heat to your hammer, your hammer spring will most likely be ruined and will need to be replaced - you cannot get access to the spring to change it without specialist tools. If you are told to "just" cut a slot across the top of the anti tamper so that you can screw it out, please note, damage to the top of the adjuster (looks like a thin skirting surrounding the anti tamper) will restrict the tension adjuster from retracting into the hammer, likewise just trying to "pinch" the anti tamper to try and pull it (see picture) will damage the edge of the adjuster. The adjuster needs to be straight to retract - if it is mushroomed or mis-shapen, it may not be able to retract - the adjuster bar inside the unit is VERY thin, if you turn it too hard, it WILL snap, which means you will need to replace the whole hammer assembly (approx £65) and you are back to square 1.
If you have successfully removed the anti tamper, or it has fallen out and now your power is all over the place, this is because your adjuster is now "free spinning" and everytime you take a shot, the adjuster bar is moving slightly - so your power will be going up and down.
If you can confidently remove the hammer assembly from your HW110, send it to us to remove the AT for you - we only charge £60. If you CAN'T remove the hammer assembly but want to be able to control the power output on your HW110, just send us the gun, we will remove the AT and set your power output to approx 11.5 ft lb for you - we only charge £65 - we can even add a titanium air tube whilst we have your gun so your gun is lighter and you get more shots! If you want us to carry out a full service & remove the AT - we only charge £125. We supply a professional AT removal service using the correct tools. Check our SERVICE page for more details or contact us.
(Left) Attempted AT removal resulting in damaged adjuster. (Right) Repaired by HW100Tuning.
using your fill probe - important!
We are seeing a lot of air cylinders coming to us for service because users are not putting lubricant on their fill probe when they are filling their air cylinder. Dry bits of rubber are shearing off the probe & getting blown into the fill valve - debris in the fill valve will cause a slow or fast leak & can also stop you from filling the cylinder with air eventually. If you look in the Weihrauch User Manual, it will tell you never to oil your threads, valves or charging equipment for the air cylinder as there is a danger of explosion. This is because a lot of people don't realise that you can't just put ANY old oil or grease on your PCP - it has to be a VERY specific type of oil/grease - it has to be inert (chemically inactive) & therefore not dangerous to use on the fill probe. ALL rubber oring seals work better with a little bit of grease/oil on them - including the fill probe! See below for which oils/grease are safe. PLEASE, make sure your fill probe is clean. Any bits of muck on your fill probe are going to get blown into your fill valve.
HW100tuning Brass Fill Probe & Seals
Oils, Lubricants and Grease
NEVER put WD40 on your gun!
Only special lubricants/oil/grease specifically designed for pcp-air guns should be used. These are sophisticated oils specially formulated for this purpose. Of the hundreds of oils available, only a few have the proper viscosity, lubricity, lack of acids for use in fine quality pcp-air guns. Our workshop recommend Molykote 33M or our own Professional Airgun Lube - it is perfectly inert (chemically inactive) silicone based and perfectly safe to use on your PCP - even on the fill probe seals.
Never oil the connecting threads and valves of your rifle’s air cylinder and always protect the thread and inlet valve with the dust cover cap provided. That goes for the original Weihrauch cylinder AND our Titanium Cylinders. ALWAYS lube your fill probe with a silicone based oil/grease - otherwise dry bits of rubber from your probe can shear off and get caught in your fill valve as mentioned above.
HW100tuning Airgun Oil - PCP Safe
What is leaking - the gun or the air cylinder?
The easiest way to determine whether it's your gun OR theWeihrauch air cylinder that is leaking on your HW100 is to take the air cylinder off the gun, put some air into it, pop a balloon over each end of the cylinder, making sure that you cover the fill port and the gap where the end cap is screwed onto the tube (see picture). Check that the balloons do not have any tiny holes in them, leave it for a few hours and if either of the balloons inflate, you know that it's your air cylinder that is leaking, and you also know which end is leaking! If it doesn't inflate - you have a leak on your gun. The first seal to replace is the 2665d - the one that you can see inside the block where you screw your cylinder in. Be careful taking the old seal off - don't scratch the brass valve! If it's still leaking after that, try a full service seal kit - or send it to us!
Detecting a leak on the Weihrauch HW100 Air Cylinder
WHY IS MY GUN FIRING ITSELF?
You have most likely smashed the sears. If you have undertaken any work to the gun, ie. replaced the anti tamper, when re-assembling you MUST make sure that the trigger unit is NOT in a cocked state (press the trigger before attaching to the gun). If you fit the trigger section to the gun when it is cocked you WILL smash the trigger sears - usually the middle sear.
How do you know if you have smashed the sears? On cocking the gun, when you push the cocking lever forward, the gun automatically fires itself (this is because the sear adges are smashed and there is nothing for it to "latch" to).
Weihrauch HW100 with a chipped middle sear
Fill the Air Cylinder From a Dive Bottle or Pump?
Weihrauch recommend that you use "Divers air quality only" to fill your air cylinder - this is because it has a VERY small moisture content - you can only get this quality air from a dive bottle. Most pumps can only guarantee to provide air that is 90% moisture free - even with a dry pack filter attached.
Any time that you fill your cylinder from empty, remove it from the gun to fill with air 150 to 200bar, then screw it back onto your gun. This is so that the exhaust valve gets a good shot of air to create the best seal. You should do this anytime that your air cylinder has completely emptied to avoid leaks…
JSB Pellet Label Explained
On the back of the tin of JSB pellets you will find a sticker with three sets of numbers (JSB Exact Jumbo Cal .22 pictured):
1st Number: 15050017
2nd Number: 1
3rd Number: 5.52
The 1st number is broken down into the following:
- 15 = The number of the pressing die that was used to make the pellets.
- 05 = Production Employee ID.
- 00 = Quality Control Employee ID.
- 17 = Year of production.
When buying pellets, look at the last 2 digits for the year of production - try and get the newest pellets you can - JSB had a "bad batch" in approx 2015 where the domes on the pellets were not as full as they should be and gave very poor results.
The 2nd number (1) is the manufacturing batch number.
The 3rd number is the calibre head size 5.52.
Free Support
We understand that it can be frustrating when your beloved air rifle isn't working as it should - whether you need it for work or for play. We spend a lot of time offering free support - and are happy to do so - but if you want to send us £1 (or whatever, it's entirely up to you) to say "thankyou" we are always most grateful...
