Airgun Accuracy

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Walther pressure regulators

I got some questions about the internals of the different Walther pressure regulators so I thought it would be good to show some pictures on these pages.

I have seen 6 different Walther regulators for the LG300 and LG400 rifles:

  1. 7,5J MK1: The 7,5 Joule / 6 FPE old version, the 7,5J MK1. These have a darker “bronze” like color and no ring grooves on the outside. Are made out of one piece and there is no pressure adjustment screw.
  2. 16J MK1:The 16 and 21 Joule / 12 fpe old version, the 16J MK1. These have the “bronze color”, no grooves and are much longer compared to the 7,5J MK1. The 16J and 21 J MK1 can be split in two halves and the output pressure can be adjusted with a set screw.
  3. 7,5J MK2: The 7,5 Joule new version which I will call the 7,5J MK2. Has a silver color, ring grooves and is made of two halves that can be unscrewed to adjust the output pressure from the original 70-75 Bar setting to at least 95 Bar. 75 millimeter long (without cilinder probe).
  4. 16J MK2: The 16 Joule new version which I will call the 16J MK2. Silver color, ring grooves, made of two halves. Is 10 millimeter longer (85mm in total) compared to the 7,5J MK2. Has 14 Belleville washers inside.
  5. 21J MK2: The 21 Joule new version which I will call the 21J MK2.   Same as the 16 Joule but has 21 Belleville washers inside and a longer piston / plunger.
  6. LG400: The Walther LG400 rifle has it own new type 7,5 J / 6 fpe regulator, the 7,5J LG400. Silver color, wider ring grooves. Out of one part with an pressure adjustment screw at the back.  The internals are exactly the same as the 7,5 and 16J MK2. Adjustable from the original 72 Bar setting to at least 112 Bar.
Regulators from top to bottom: 16J MK1, 7,5J MK1, 7,5J LG400.

Regulators from top to bottom: 16J MK1, 7,5J MK1, 7,5J LG400.

The LG300 MK2 regulators. Bottom the 16J MK2, on top the 7,5J MK2. Notice the 10mm difference in length.

The LG300 MK2 regulators.
Bottom the 16J MK2, on top the 7,5J MK2. Notice the 10mm difference in length.

The 16 and 21 Joule MK1 and MK2 regulators are 10 millimeter longer to get a larger volume in the secondary pressure chamber. In combination with the higher output pressure this supplies more air per shot to reach a higher velocity of the pellet. The valve, valve return spring, air transfer ports and hammer spring are the same for 7,5J and 16J rifles. 21 Joule rifles use a stronger hammer spring.

I found that 7,5J regulators are usually set to 70-72 bar output pressure. 16 J regs are set to 83-85 bar and 21J regs are set to 100 – 110 bar output pressure.

After the very first introduction of the LG300 rifles in 1999, the 7,5J and 16J MK1 regulators suffered from a lot of problems with the consistency of the output pressure. After what I think was about 2 years or so Walther came with the new MK2 regulator. The main difference that I see is the different shape of the valve inside the regulator.

  • The MK1 has a cone shaped valve with an o-ring while the MK2 has a flat valve sealing area with a flat seal.
  • In the MK1 the piston seal sits in a groove in the housing. In the MK2 regs the piston that holds the belleville springs (a.k.a DIN 2093 or disc springs) has a groove with an o-ring seal.
  • The MK1 regs have a brass threaded part to screw the air cilinder on. In the MK2 regs this part is from stainless steel which is less prone to damaged threads.
7,5J MK1 regulator internals

7,5J MK1 regulator internals. Notice the cone shaped valve and piston without o-ring.

Regulator WalLG300cut

7,5J MK1 regulator. Notice the position of the piston seal.

7,5J MK1. Better view of the cone shaped valve

7,5J MK1. Better view of the cone shaped valve that is typical for the MK1 regs.

16J MK2 reg internals. Notice flat valve and seal and o-ring on the piston

16J MK2 reg internals. Notice flat valve and seal and green o-ring on the piston.

Opened 16J MK2 regulator on the reg tester. The red screwdriver is on the locking screw. The hex key is on the pressure adjuster.

Opened 16J MK2 regulator on the reg tester. The red screwdriver is on the locking screw. The hex key is on the pressure adjuster.

The regulators on new LG300’s (from about 2012?) and the LG400 regs have a small filter in the inlet to keep dirt out of the reg internals.

LG400 regulator. The yellow part is the filter.

LG400 regulator. The orange part is the filter (purple part is the firing valve).

LG400 regulator internals

LG400 regulator internals

I measured the internal parts of the LG400 regulator and they are exactly the same as the parts used in the LG300 7,5J MK2 and 16J MK2 regulators. So for ordering parts of the LG300 MK2 and LG400 regulator you could use the part numbers (second column) in the table below. Please inform your supplier about the regulator type (LG300 or LG400) you want parts for. Just to be sure. These drawings and tables are from the Walther website.

Price codes (like A or U1) are in the right hand  column of the parts list. Corresponding prices are in the table below (A = 2,20 Euro, U1 = 155 Euro). Prices are for the period April 2013 – April 2014.

LG400 regulator exploded view (from Walther Ersatzteilliste)

LG400 regulator exploded view (from Walther Ersatzteilliste)

LG400 Walther Parts list (Ersatzteilliste 2777398)

LG400 Walther Parts list (Ersatzteilliste 2777398)

Price codes for Walther spare parts (as of 2013)

Price codes and related prices in Euros for Walther spare parts (as of 2013)

My favorite supplier for Walther spare parts, including those for the regulator, is Judith Billharz from The service is very quick, it usually takes 4 days before the parts land on my doormat. Shipping costs are reasonable: 7 euro for a small package. The web-shop is here: . But I usually send her an email with the part numbers from the Walther “Ersatzteilzeichnungen” that are also on the website. German or English language are both okay for the email. The email address can be found here:

Dis-assembly of the LG300 MK2 pressure regulator



The Walther LG300 pressure regulator is build out of two halves that are screwed together. To adjust the regulator output pressure these halves need to come apart because the setscrew and locking screw are inside. From the factory these halves are screwed together VERY TIGHT. To take the two halves apart I made a special tool from an old 17mm spanner and use v-groove jaws in a big bench vise and protect the reg from damage with thick leather in the jaws.

Regulator in bench vise with spanner on

Regulator in bench vise with spanner on

Spanner close up

Spanner close up, notice protective plastic sheet

The spanner has two 5,5mm holes for the high strength M5 bolts that bolt into the reg. These bolts are made to length so they do not bottom out but are as long as possible to give maximum hold in the threads. Between spanner and reg I put some plastic sheet to prevent scratching the reg surface. The bottom of the jaw of the spanner has been cut out so it does not touch the protrusion of the reg. This protrusion needs to give an airtight seal so must not be damaged.

Reg opens

Reg opens

Reg opened, set screw is visible.

Reg opened, set screw is visible.

Other half, secondary or low pressure chamber

Other half, secondary or low pressure chamber

Recently I do NOT use the spanner method anymore. See below for a safer method. I heard that people also use two rubber strap oil filter wrenches with succes.

When the reg is opened like this the output pressure can be adjusted. Undo the locking screw first and then adjust the set screw with a 4mm allen key. Clockwise increases the output pressure. I found that 1/8 of a turn gives about a 10 bar higher pressure.

Four 2,5mm drills to open the reg.

To service the regulator internals you need to open the other side of the regulator. This is the side that the pressure cilinder screws onto. This side has 4 small holes. In these holes I put 4 drill bits of 2,5mm diameter.

Then I put an adjustable spanner on flat against the regulator. Adjust the width of the jaws so it touches all four drillbits but does not bend them.

Then I put an adjustable spanner on flat against the body of the regulator. Adjust the width of the jaws so it touches all four drillbits but does not bend them.

7,5J MK2 reg taken apart

7,5J MK2 reg taken apart

I measured some sizes of the parts:

7,5J Reg Belleville O.D. size

7,5J Reg Belleville O.D. size 9.64mm

7,5J Reg Belleville thickness 0,50mm

7,5J Reg Belleville thickness 0,50mm

7,5J Reg Plunger length: 15.77mm

7,5J Reg Plunger length: 15.77mm

The plunger is 15,75mm long. The larger dia part is 6,45mm in length and 9.95mm in diameter. The diameter of the stem is 4.97mm and is 9,32mm in length. The measured I.D. of the 14 Belleville springs is 5,32m. The measured O.D. is 9,64. The thickness is 0,50mm. Looking at the info from some large suppliers or producers it looks like the Bellevilles are probably sold as DIN 2093 with the size being 10 x 5,2 x 0,5.

EDIT: Based on a remark by Heiko I have tried to fit some 10×5,2×0,5mm belleville springs in the Walther MK2 reg and they do NOT fit. Has to be the smaller 9,64mm OD that I measured. Not found where to buy these, except at ridiculous price from Walther.

The 7,5 Joule MK2 regulator and the 16 Joule MK2 both have 14 Bellevilles that are stacked like:

low pressure side-  (()) (()) (()) (( -high pressure or 300 bar air cilinder side [put the 2 concave discs “((” on the plunger / piston first]. These regulators can be set from 45 to 85 bar output pressure.

LG300 Regulator Belleville stacking order

LG300 7,5 and 16 Joule Regulator Belleville stacking order. Piston is in red colour.

The 21 Joule MK2 regulator has 21 Belllevilles that are stacked like: low pressure side- ((( ))) ((( ))) ((( ))) ((( -high pressure side. These can be set form 90 to 115 bar output pressure.

21 Joule Mk2 Belleville stacking

21 Joule Mk2 Belleville stacking

The 7,5 Joule LG400 regulator has exactly the same internal components as the 7,5 and the 16 J MK2 reg. The belleville washers are stacked the same way as well. (this information is factory confirmed now)

Regulator Tester

Made a drawing and some pictures of my reg tester.

LG300/400 reg checker dimensions

LG300/400 reg checker dimensions

Regulator Tester; reg side

Regulator Tester; reg side

Reg tester; valve stem side

Reg tester; valve stem side

This model reg tester can be used for both the LG300 regs and LG400 regulator.  It is made from 20mm thickness aluminum. For LG400 regs I use the original Walther regulator seal on the reg tester. For the LG300 reg I add an extra rubber washer that is actually a 13.30 dia x 3,20 thick rubber tap seal. This tap seal goes under the LG300 reg seal. The valve is made of a M3 countersunk screw with a small o-ring underneath to seal it.

The manometer is a 60mm dia. Wika 160 bar manometer with 1/4G (= 1/4 19tpi BSP.F) thread.

To operate the valve of the reg tester I bounce the whole assembly of air cilinder, regulator and reg tester on a vinyl floor. The lift height from the floor is only a few centimeters.

See this video for the test of an LG400 regulator set at 100 bar. And no, i’m not damaging my wooden floor 🙂

RogB Regulator Tester; Made on a pillar drill.

RogB. made a regulator tester using only a pillar drill. He has posted some usefull comments below. Here are some pictures from RogB’s reg tester.


RogB’s regtester, backside.

RogB's reg tester with LG400 regulator

RogB’s reg tester with LG400 regulator

In 2008 the Walther factory published a fact sheet with instructions how to change the pressure regulator on the LG300 rifles:

Changing Reg_Page_1Changing Reg_Page_2Changing Reg_Page_3

Opening the LG300 Regulator

I used to open the LG300 regulator using a bench vise and v-grooved aluminium jaws protected by thick leather. The risk is then to close the vise too tight and the reg body will become oval. To prevent this I always closed the bench vise slowly while turning the spanner until the regulator stopped slipping.

But there are much better options!

Sidney from Belgium provided me with some 35 millimeter clamps normally  used for large high pressure tubes. With some paper  wrapped around the regulator body this setup will clamp the regulator all the way around without any risk of damage. Put one side in the bench vise and put a big spanner on the other side to open the reg (counterclockwise).

LG300 regulator in 35mm hydrualic tube clamps

LG300 regulator in 35mm clamps

35mm Hydraulic tube clamp

The 35mm clamp openend

But it can even get better! Phil from the UK made me a very nice set of tools to open the regulator and a regulator tester as well. Thanks again Phil. I owe you.

Phil G.'s clamp and reg tester.

Phil’s clamp and reg tester.

Phil G.'s Clamp and Reg Tester

Phil’s Clamp and Reg Tester

Phil his clamp and the reg tester are beautifully made of aluminium. Both have a flat to put a big spanner on. Some paper or tape is put between the clamp and the reg body to prevent scratches. Phil also made me a tool with four pins to open the input / cilinder side of the regulator.

Phil's tool to open the cilinder side of the regulator.

Phil’s tool to open the cilinder side of the regulator.

Opening the input side is not that difficult as long as you take care not to damage the threading with your spanner. Press the spanner against the reg body when turning it. It is tight but does not take overly much force (like splitting the LG300 reg does) .

For H. as an answer to his question: It can be done with the reg on the rifle but I would NOT advise to. It is not much work to take the reg off (two M5 / 4mm Allen key) and it saves a lot fiddling later on when you want to take out the reg internals. It also saves you from potentially scratching or damaging your breechblock or barrel surfaces.

It can be made even easier when you first back off the pressure adjustment screw. This reduces the force on the belleville springs and thus on the threads of the input side.  The disadvantage is that you loose your original reg pressure setting when loosening the set screw. You could of course measure the depth of the setscrew in the reg body with a caliper to be able to return to the original setting. Counting the number of turns is usually not a good method because a small 10 degree turn already makes a large difference in output pressure.

 The Walther LG300 21 Joule MK2 regulator

I had a chance to open an MK2 21 Joule regulator to see the internal difference between the 16 and the 21 Joule regulators. I first checked the output pressure setting and found it to be 100 Bar (factory setting). I used Phil’s tools on both the reg and the input side and they worked flawless to open the regulator without any damage.

First thing I noticed after opening was that the output pressure setscrew was poking 4.20 mm out of the reg body. On the 16J regs this screw sits completely inside its threaded hole.

Walther 21 Joule regulator opened

Walther 21 Joule regulator opened

I opened the reg from the fill side and found 21 Belleville springs or disc springs on the piston. The 16 Joule reg has 14 of them. To house these 7 extra Bellevilles the 21 Joule regulator has a longer piston / plunger: 19,96 mm. The 16J reg has a piston that is 15,77 mm long. This also explains why the setscrew is poking out: Walther uses the same setscrew for all MK2 regulators and to make space for the longer piston it sticks out of the reg body.

Walther 21 Joule regulator piston and belleville dimensions

Walther 21 Joule regulator piston and belleville dimensions

The Belleville springs are the same for all the MK2 regulators as you can see from the dimensions in the picture.


42 thoughts on “Walther pressure regulators

  1. Thanks Sven for all the helpful information, especially for the reg checker details 🙂

    • The reg checker is working well, the two problem areas were getting a good seal on the firing valve and the dimensions on the drawing.
      I made 2 at 35x35x25 and both were very difficult to drill and had to be scrapped. I think the minimum size that works best is 50x35x35. I had a 35×35 bar which is 107 long and is easy to hold and drill.
      The valve requires a very good seal in order to stay air tight, so the face where the O ring seats needs to be lapped flat, rather like lapping an engine valve seat.
      It is definitely worth making one, it is not expensive and easily done as long as you have a pillar drill.

      • Thank you for the valuable comments Roger. I made mine on a lathe and milling machine. But you showed it can be done with a pillar drill. Could you post a picture?

  2. I would if I knew how to post a picture on here 🙂

  3. Hi Sven, is it maybe better to open the LG300 Reg with such Tool:$_12.JPG

    Because of when you open the Reg you said it needs a good amount of Force to open it,
    Maybe the Boltholes became a oval-shape and then they are no more round and get finally damaged?

    • Hello H.,
      The two rubber band tools that I tried myself did not work. They slip. But I have been very fortunate and both Phil and Sidney (Thank you very much gentlemen) provided me with a set of tools that are safe to use and much more sophisticated than the bench vise shown in the pictures above. I will take some pictures and post them here.

  4. Ok, thanks. When i want to service the Reg and put 4 2,5mm drill-bits in the holes, does it need much force to open the front Screw?
    Can i do that without remove the Reg from the gun?


  5. Fantastic news about the hydraulic clamps, I will order some! Also a lovely job on the clamp/reg tester, that is quality work. Thanks for posting this Sven.

  6. Thank you Sven ! Very cool things!
    But are you really sure that i must turn the clamps clockwise?? not as normally anti-clockwise??

  7. Ok, now iam really wise about that. But one thing i want to know, the hydaraulic clamps are sold as 2 different models – the heavy Type C and the Light type A.
    Can you make a photo where i can see the inner sides of the hydraulic clamps?

    Thank you very much! I hope i dont annoying you.



  8. Hi Sven, can i use this Tool to open the Pressure-Side ???: [img][/img]

    • Hi Heiko,
      Yes, at first sight that looks like a useful tool. There are two remarks: The diameter of the two pins should be close to but not over the hole size in the reg. And the end of the legs are quite wide and could touch the threading of the regulator. May need to remove some material there.

  9. Thanks Sven!
    But now i have some doubt, because the are not 4 holes for fun, i think when i use the 2 bolt tool the holes became an oval-shave and get finally damaged… i have tried
    it with 4 drill-bits and with the reg on the rifle, but no way too tight… i have nothing damaged but cant still open the front…. No idea at the moment.

    When i remove the reg from the rifle and put it in the hyd-clamps, what is the torque for the M5 Bolts for reinstall??

    Thank you!!


  10. Hallo Heiko,
    As mentioned above: Take the reg off the rifle when you want to work on it. And I agree: When there are 4 holes you should use them.

    The Walther instruction leaflets in the pictures above do not give advise for the torque for the M5 reg bolts. And a torque wrench will not fit anyway because the sides of the bolt heads are too close to the breechblock. I use quite a light force with a normal sized allen/inbus key, not the long arm one. Do not overdo it. It is just M5 in aluminium. The risk is to strip the threads in the reg. You may think that this 110 bar reg pressure needs a lot of force to keep the reg in place. But it does not! The area that the pressure pushes onto is only 0.71 square centimeter. 110 Bar is 110 kilogram per square centimeter. So 0.71 x 110 = 78 kilogram of force. The two allen bolts can easily hold this. (A class 8.8 bolt has a 6400 Bar yield strength (and a 8000 bar tensile strength) This is of course the strength of the bolt and not the total construction of the reg and breechblock. But it indicates the forces we are dealing with.)

    Push the reg against the breechblock and tighten both the bolts by screwing both of them alternatlely. You will feel when the reg sits tight against the breechblock and has compressed the o-ring. That is enough.

  11. I was going to order 2 sets (14) disc springs to keep as spares when I found out the price €3.50 each disc from Walther! Disc springs in the size you measured are £15 per 100 in the UK.
    Have you tried any alternatives? I think it is beneficial to replace the Bellevilles when you do a full reg overhaul.

  12. Hi Roger,
    Yes I know the price Walther charges for the bellevilles / disc springs is ridiculous. That is actually the reason I put the dimensions of the disc springs on this page. Much cheaper to buy them elsewhere. Look for DIN 2093 on the internet and you will find numerous suppliers.
    I have not tried alternatives for the originals. The reason is that I do not believe the disc springs in a Walther regulator will wear over time when used at the pressure settings between 70 and 95 bar. They make only a very small movement and are not overly compressed.
    I think it is even better to keep using the old ones. These are already “broken in”.
    I know many 10 meter airgun shooters that shoot their Walthers three times a week for over 60 shots. I did do that myself in the past with my 10m LG300. That’s almost 10000 shots per year. And they do not replace or service their regulators or the disc springs. I do not shoot a lot, only once a week. But my Dominator is from 2001 and got a new MK2 type reg in 2004. I never serviced that MK2.

  13. A good point well made. I will leave the Bellevilles and just get the other bits. Thanks Sven 🙂

  14. Just one further thought on this Sven. In FT and HFT we use these rifles outdoors far and beyond their intended 10m indoor design specification, in temperatures well below zero to +35 perhaps, along with getting soaked with rain many times a year, then transported home in a wet bag. In HFT we are laying down in the mud quite often so dirt easily finds its way inside. It is not impossible for corrosion to take place internally, even inside the reg, due to condensation and so on.
    It is worth bearing in mind that a thorough service after extended outdoor use may need to include the replacing of parts that 10m shooters find are in perfect condition.

    • You are right Roger. When there is any corrosion visible on any part inside the regulator it should be replaced. And the chance that moisture enters the regulator is much bigger in HFT or FT outdoor circumstances than indoors.
      The venting hole in the regulator is a possible entry port for moisture. And it leads directly to the disc spring package. One of my regs has this hole located just on the top right hand side of the reg, next to the barrel. I put a small piece of thin translucent sellotape over the venting hole when shooting. This keeps rain and dirt out. And I hope it is thin enough to be pushed aside when the reg needs to ventilate. Returned at home I remove it.
      Most regulators have this hole at the bottom under the stock which gives less chance for moisture and dirt to enter.

  15. Scotch Tape being applied now, what a good idea! I have heard of regs having this rust and dirt problem so it is worth taking steps to prevent it. I also heard from Judith Billharz and she will supply the correct Walther disc springs at €2.50 each. I would rather buy 100 and give some to friends if the exact replacement DIN 2093 can be identified.

  16. Hi Sven, thanks for inspecting the 21 Joule Regulator.
    But can i only open the 16 Joule Reg and add 7 Disc-Springs and then stack them like in the 21 Joule Version, but without changing the Plunger?

    • Hallo Heiko,
      Regarding your question: No you cannot add 7 disc springs on the 16 or 7,5 Joule piston. 1 or 2 might go on but not 7. The discs will not be on the piston stem but loose and impair the reg function. But you can try to buy the longer piston from Walther. The part number in the LG400 regulator drawing is 52 for pricegroup L which is only 9,80 Euro. My guess is that the longer 21 Joule piston will be the same price. Try Judith Billharz to get this piston. She was able to help me to get other regulator internals that are not on the Walther LG300 drawings.
      Regards, Sven.

  17. Scusate ma dove posso comprare un regolatore per la mia Walther LG300 16j ? Grazie.

  18. Hello,
    Do you know if it is possible to convert a Walther LG30 to 16joule?

    • Hello Martin,
      I’m not familiar with the Walther LG30. It looks like an spin off from the Hammerli AR20, but I’m not sure. The LG30 is completely different from the LG300 so I have no idea about it’s capabilities.

      And I do not know a lot about the AR20 as well. But what I know is that there is a 16 Joule version of the AR20. The AR20FT. So it may be possible to change parts from the AR20-FT, like the hammer and the pressure regulator to get 16 Joule from the LG30. But this is all a big guess.
      I would advise to study the exploxed views and parts diagrams of both the AR20 and the LG300 at the Walther website.
      It can very well be that it is a better, and cheaper, option to sell the LG30 and buy an AR20FT.
      Good luck, Sven.

  19. Hi
    I will be rebuilding my lg300 regulator soon with genuine Walther seals, is the regulator assembled dry or do some seals have to lubricated.

  20. I will be rebuilding my lg300 regulator soon with genuine Walther seals, is the regulator assembled dry or do some seals have to lubricated. Sorry to ask you again but can not remember if any regulator internal seals were greased or lubricated in any other or was the regulator just assembled with dry seals.

  21. Hello Trevor!

    Yes the O-Rings are greased but use a Grease not an Oil. Dow 33 is a very good Grease for that job. Use it very sparingly!

  22. Thanks for the info

  23. Trevor, you can also use Molykote 111 for O-ring lubrication. It is designed for that. I’ve been using it for a few years and have seen no ill effects or poor sealing on any O-rings so far

  24. Dow 33 Medium is perfect!

  25. Important INFO: Hello Sven, today i tried to replace the Belleville Disc Springs i a 11 year old 7,5J MK2 Regulator. I bought back in 2014 some DIN 2093 10 x 5,2 x0,5 x0,75 Disc Springs (Made out of 1.1231 Spring-Steel)… so far so good, but they DO NOT fit inside the Regulator, because they are 10,0mm in outer diameter – so they are slightly to large – and dont forget when they under Pressure their diameter will increase even more!!

  26. I have an issue with my 5 year old LG Domminator 16j which I believe is reg related:
    I tried to fire it several times and got a weak “thunk” sound and found the pellet was being fired but at a VERY low velocity.
    At 10 yards using JSB 8.4 pellets I was striking a full 5cm below the point of aim.
    I chrono’d it on my combro which gave a reading of 380fps. I tried it later and it went up to 765 followed by 850 then 855 then 1050(!!) then back down to 520!
    Anyone on here that could could point me towards the likely cause and, hopefully cure?
    Or is it new regulator time?

    • Hello Jon,

      It can be the regulator, and that’s most likely. But it could also be the striker or striker spring. Because the striker and spring can be checked easily I would suggest to do that first. And please check if the barrel is still fixed in the breechblock. When the barrel is loose the transfer port changes position and can get misaligned with the port in the block. Check the three screws on top of the block that hold the barrel. I’ve heard about a loose barrel once before.

      But as you suggest it’s more likely to be the reg. Dirt, dust or moisture can have entered through the cylinder connection or through the small venting hole. Reg’s can be repaired and the parts needed can be ordered at Schiesssport Billharz in Germany. Look at the LG400 drawing to see an exploded view of the internals with part numbers, that are the same for the LG300 and LG400 regs.

      The problem is to open the regulator without damaging the threads. You need a special tool for that. And the other problem is to set the reg to the right pressure after the repair. You need a reg tester to do that.
      Most people do not own these tools and that makes it hard to service a reg yourself.

      I can repair the regulator for you. If you’re willing to send it to me and pay for the return shipping and parts needed. When you’re living in the UK you can also try to contact Hmangphilly on shooting-the-breeze or Trevor Ford.

      Otherwise a new reg can be ordered from Schiesssport Billharz or other shops in Germany. They are about 170 to 180 Euro.

  27. Hello Sven,
    what Belleville Disc Spring do you use for the Reg, beacause of the 10 x 5.2 x 0,5 dont fit??

    • Hello Heiko,
      Many thanks for your comment.
      I use the original Walther belleville springs (from a 7.5Joule LG400 reg that I do not use.
      You are right, I tried a 10mm outer diameter and that does not fit.
      When I find the right size and a place to order form I will let you know.
      regards, Sven.

  28. Hello Sven,

    I have a LG300 with the Mk2 16j reg. I have a very slow air leak coming from the vent hole in the reg. I have a lot of experience building and repairing Air Arms regulators, and using the diagrams and the photos on this thread I think the parts I need are 2654326 – disk, a 13×2 O ring and a 6×2 O ring. Are there any other parts I should replace while I have the front of the reg off?

    Thanks, Neil

    • Hello Neil,
      As far as I know are those three parts the ones that wear.
      If your reg has an inlet valve that has a conical sealing side than its worthwhile to replace it by the new style that has a flat side. It’s not expensive.
      Good luck with the job,

  29. Thanks Sven,

    I’ve done a lot of work on Air Arms regs over the years, so it was not too hard to figure out the routes that air might take, but it’s always worth asking someone who really know the regs inside and out. I’ll take a look at the inlet valve while I have the reg out.


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