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:
- 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.
- 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.
- 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).
- 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.
- 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.
- 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.
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.
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.
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.
My favorite supplier for Walther spare parts, including those for the regulator, is Judith Billharz from www.SchiessSport-Billharz.de. 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: http://www.schiesssport-billharz.de/shop/de/Ersatzteile-Walther/Luftgewehre . 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: http://www.schiesssport-billharz.de/shop/de/Unsere-AGB
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.
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.
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.
I measured some sizes of the parts:
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.
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.
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)
Made a drawing and some pictures of my reg tester.
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.
In 2008 the Walther factory published a fact sheet with instructions how to change the pressure regulator on the LG300 rifles:
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).
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 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.
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.
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.
The Belleville springs are the same for all the MK2 regulators as you can see from the dimensions in the picture.