Airgun Accuracy

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Walther LG 300 conversion to 16 Joule

Converting Walther LG300 and LG200 airrifles from 7,5 to 16 Joule

(originally posted on the Shooting-the-Breeze forum: )

I have converted two Walther LG300’s and a LG200 from 7,5 Joule/5,5 footpound to 16 Joule/12 fpe field target rifles. All these 3 air rifles already had the new MK2 type regulator (with the ring grooves on the outside).
This new type 7,5 Joule regulator can be set from the original 70 bar setting to a 92-95 bar output pressure. This will allow you to get to 16 Joule / 12 fpe without any other conversion to the rifle. You only need to increase the preload on the hammerspring while shooting it over a chronograph.

The Walther LG300 Dominator is a dedicated field target rifle has a MK2 regulator that is longer than the 7,5J MK2 regulator. The rear part, the secondary/low pressure chamber, is 10mm longer for the 16 Joule/12fpe regs compared to the 7,5J regulator. The number of grooves on the outside is the same however. The 10mm more length means more air to move the pellet. (picture by RobF from

LG300 long and short MK2 regulators compared

LG300 long and short MK2 regulators compared

But this does NOT mean that you need to buy a 16 Joule regulator to convert a LG300 from 7,5 to a 16 Joule field target rifle. When you set the MK2 short ringed type 7,5J regulator to 92-95 bar you will easily get 12 fpe from an LG300 or LG300 XT. I have done 2 recently with good result.

I even found an advantage in using the short 7,5J MK2 regs: The rifles are less noisy compared to a long 16 joule reg set at 80 bar. I think the long 16 joule regs are using to much air for a shot. The excess air leaving the muzzle and causing the extra blast noise.

The older MK1 type 10 meter 5,5fpe regs have no grooves, are shorter and cannot be used for a field target conversion to get 16J from the LG 300. They need to be changed to the new MK2 type. An 165 euro part which is set to 80 bar for the 16 Joule Walther Dominator field target rifles. This 80 bar reg setting is not high enough to get 12 fpe with the standard hammer and 42 centimeter / 16,5 inch barrel. With the original 80 bar output pressure I got the LG300 up to 220 m/s  (722fps) with the JSB Exact 8.3 grainers. Original 16J/12fpe Walther Dominators have a longer barrel (49 cm / 19,3 inch)  and a heavier hammer/valve striker. But when the reg is adjusted to 92 bar the LG300 rifle will get to 16J/12 fpe easily.

I made a regulator tester and a special tool to open the reg to adjust the regulator output pressure. But I found that all these 3 regs needed the same three/eights of a clockwise turn on the set screw to get to 92-95 bar. So it can be done without a reg tester.

Reg tester for Walther

Reg tester for Walther LG300

Opening the reg is not easy. It is screwed together very tight. I clamp the cilinder side of the reg in a big bench vise with aluminum V-grooved jaws and thick leather around the reg to protect it. Then use a special made tool which has bolt holes at 10 degrees angle and use high strenght M5 bolts using the full threaded length in the reg to unscrew the two parts of the regulator.

LG300 reg opened. Screw 1 sets the output pressure. Screw 2 is the locking screw.

Walther LG300 reg opened. Screw 1 sets the output pressure. Screw 2 is the locking screw.

To get a good working 16J rifle you also need to change the valve seat from the original blue or green type to the harder white PTFE type. This is a 5 euro part. The Walther part number is 2732505.

The only problem that is left by then is the cocking lever. This will interfere with the scope mounts or turret on a field target rifle when cocking the hammer. I shortened the original cocking lever, put in a M4 threaded hole and added a pin so it looked like an original Dominator cocking lever.

Modified LG300 Cocking lever. Notice it still rests on the stop pin.

Modified Walther LG300 Cocking lever. Notice it still rests on the stop pin.

The position to which it can be shortened is determined by the pin in the breech block that is the stop of the lever in its down position. It still needs to rest on this pin after shortening it.
The cocking lever is made from hardened steel. To be able saw, drill and thread it I heated the part that needed to come off while keeping the other side in the bench vise to protect it from the heat of the blowtorch so that part would stay hardened.

Dominator offset cocking lever

Dominator offset cocking lever

You can also choose to order an offset cocking lever (Walther part no. 2688638) for about 70 euro. But then you most probably need to adjust the barrel position back and forth in the breech so the tapered loading bolt with o-ring closes nicely in the taper of the breech of the barrel .
This is not difficult (3 screws on top of the breech block) but sometimes the barrel is out of adjustment range because of the new cocking lever. Meaning the transfer port in the barrel does not line up nicely with the transfer port in the breechblock. In that case you need to order a different size loading bolt lever. There are three sizes of this part: 0, 1 and 2. They are called “Spannstuck” in german. Position 8 in the exploded view drawings. The walther parts are 2605864 Spannstück 1, 2605856 Spannstück 2, 2607701 Spannstück 0. The number is stamped on them. I have seen them here: for about 14 euro each.

My own converted LG300 and LG200 field target rifles both shoot very well. I found an nice batch of JSB Exact with die number 80 that shoots 15mm/0,6inch 5-shot groups at 50meters/55 yards from the sitting field target position regularly with the LG300. Just a bit better grouping than I was able to do with my Steyr and EV2.

Groep LG200 IMAG1450

16,60 millimeter 5 shot group at 50 meters with the LG200 at 16J (16,60 mm outside to outside, CTC this would be 12,10mm group) shot outdoors from the sitting FT position.

So in short: A field target conversion of the Walther LG300 and LG200 can be done with good result, but it takes some tools and mechanical handiness.

New Reg Tester made

I made a new regulator tester, (reg tester / reg checker) for Trevor. I used an LG400 valve in the reg tester to simulate the shot and cycle the regulator.

Reg tester Walther LG300

1. Reg tester Walther LG300 parts: Body, 2 x M5 bolts, LG400 valve, valve return spring, BS012 o-ring and my own brass bling valve hammer (not included).

2. Reg tester Walther LG300; Regulator side

2. Reg tester Walther LG300; Regulator side. Valve and o-ring in position. Valve return spring not in this picture.

Reg Tester Walther LG300; Valve return spring in place.

3. Reg Tester Walther LG300; Valve return spring in place.

3. Reg tester Walther LG300; Valve side

4. Reg tester Walther LG300; Valve side. Hit the valve stem with a small hammer or piece of metal   and the reg will cycle (valve stem is made from hardened steel ).

Reg Tester LG300; Regulator and cilinder mounted.

5. Reg Tester LG300; Regulator and cilinder mounted. Pressure is set at 100 bar to test for leaks. 100 bar  is not an advised reg output setting for shooting 16 Joule / 12 FPE.


30 thoughts on “Walther LG 300 conversion to 16 Joule

  1. Are you able to supply a reg tester please.

  2. Any news on reg tester yet.

  3. Hi Trevor,
    Your reg tester is ready, tested and on its way to your address. See the pictures above for placing the valve, o-ring and spring.
    Thanks for the order, Sven.

  4. Good morning.
    Really interesting article CONGRATULATIONS!
    I try to ask a question:
    After adjusting the regulator to 92 bar, it is possible that with the lowering of the cylinder pressure regulator does mark the tester less bar?

    Cylinder 200 bar – 92 bar regulator = ok;
    Cylinder 150 bar – 92 bar regulator = ok
    Cylinder 140 bar – 90 bar regulator = ???
    Cylinder 120 bar – 88 bar regulator = ???

    This is what happens to me if I connect the controller to the tester with load cylinder at different pressures.
    What’s wrong? what can I do?

    • Hi Mario,
      2 bar difference over a cylinder fill is okay. And it will not have an effect on accuracy.
      The 4 bar difference between 150 and 120 bar input pressure is bigger than I normally see in a good regulator.
      I presume this is an 7,5 Joule (short) regulator? Because you set it to 92 Bar? Does it have the ring grooves on the outside?
      Do you test by screwing the cylinder on and off or does your tester have a valve to cycle it?
      In a rifle the pressure drop caused by a shot is about 20 bar. Does your reg checker reach this pressure drop?

      • Good morning!
        I try to explain my situation:
        I own a Walther LG 300 with regulator mk2 by 7,5j modified to get to 16 j.
        After a year of use, the weapon gave me a lot of problems and I decided to open the regulator. I have not found the problem, even after various tests, I decided to buy a regulator mk2 16 j. This regulator was set to 81 bar.
        Following the directions of your article I brought the internal adjustment to 92 bar and I got the results of the tests that I wrote in the previous message. Unfortunately my tester is not like yours. The data were obtained by downloading the cylinder at intervals and I got the mk2 200 to 150 bar is stable at 92 bar while later, begins to fall.
        I have not yet connected to this mk2 Walther but now I have a new problem. Or maybe, I found the original problem and that is that: with the mk2 by 7,5j modified, each time I connect and unplug the cylinder, a small amount of air comes out of the barrel.
        So I guess I should change the springs of the Lg 300 with those of a Walther Dominator. Or what do you recommend I do? Basically I think the problem has never been the regulator but the springs of the rest of the weapon are a 7,5j and not for a 16. Right?

      • Hello Mario,
        You do NOT need a new hammer spring. The hammer- or striker spring is the same for the 7,5 and 16 joule type of rifles. Only the 21 Joule Dominator has a stronger hammer spring.
        When air comes out of the barrel this means the valve seal is most probably not okay.
        What you need is a new Dominator valve seal. (position no. 73 part no. 2732505 “Ventildichtung” in the Ersatzteil Zeichnung Walther LG300 Dominator )
        The valve seal for the LG300 Dominator is white colour and made from a harder material than the blue or green valve seals from the 7,5 Joule LG300. This is an expensive part: 28 euro.
        When ordering the white 2732505 valve seal you may want to order the valve return spring ( position no. 85 part no. 2163900) at the same time. This is a cheap spring for 3 euro and replace it just to be sure. If you valve shows signs of wear or damage you want to replace that as well ( position 72, 2620847) which costs something like 15 euro.

        But the most important thing is to replace the valve seal with the white valve seal 2732505.

        Good luck, Sven

  5. Hi Sven this is not related to this article but as its your latest article I thought you may notice this? I am impressed by your convertion of the lg400 to 16j using the mk2 dominator reg ,so all I need is the adaptor that you make,would that be possible please. Martin G

  6. Thank you so much for the valuable information!
    I will do what you told me.
    Only two questions:
    1) you could suggest where to buy these three pieces?
    2) the regulator is ok at 92 bar ?

  7. Thanks again for the valuable information.
    I write now an e-mail.

  8. Hi
    I have purchased walther dominator 7j , manufactured 2015, i would sppreciate if someone can suggest process to change to 16j
    sincerely ashish

    • Well basically it is already written above here. But to give you a short list of what to do:
      Buy the 16 Joule pressure regulator (part number 2693038). This is original on 80 bar and needs to be set to 85 bar pressure. At 80 bar you will not get the full 16Joule. Send it to me to adjust. You can try this yourself but you need special tools to open it. It only needs a little adjustment. About 1/8 of a turn. If you go to high you will also not reach 16J. Read more in the Walther Pressure Regulators page . I can also adjust the 7.5J reg for you to 95 bar. You will reach 16J but I hear different stories about the accuracy when using the 7.5J reg at 95 bar. Some are good, some are not what it takes.

      Buy and install the white Teflon valve seal part no. 2732505.

      Shorten the cocking lever so that it just rests on the pin that it rests on in the downward position. Soften the corner to drill and tap for and M4 bolt.

      Adjust the hammer spring to set the velocity to 235 to 240 m/s (with 8.4 grain / 0.54gram pellets).

      Good luck, Sven.

  9. Ciao Sven,vorrei acquistare un regolatore di pressione per la mia Walther LG300 16j. Puoi dirmi come fare ? Grazie.

    • hi where can i buy 16j regulator online and what is the good price for it?

    • Ciao Giovanni, and Ashish

      My Italian is not that good but I think your question is where to buy a 16 Joule LG300 pressure regulator.

      The answer is that I buy my Walther parts at Schiesssport Billharz in Germany:

      Judith Billharz has a fast shipping service for very reasonable prices and her English is very good. I can surely recommend her. She is an airgun shooter herself and used to work for Walther in the past. So she knows what she is talking about when it comes to Walther guns.
      Good luck with your LG300,
      Cheers, Sven.

  10. Hello Sven,
    excuse my language but use google translate, I wanted to know if you could fulfill myself a tester reg for my regulator Walther LG300, if it were possible then we can feel by mail.


  11. Nello Sven sorry for my bad english You create for me a tester reg for my lg 300 ?

    • Ciao Allesandro,
      Yes I can make a reg tester for you. I will send you an email with further details.
      Kind regards, Sven.

      • Hallo Sven,
        Sie haben bereits für verschiedene Fans reg-Tester hergestellt. Ich möchte mich heute einreihen und bei Ihnen ebenfalls diesen Tester bestellen (für Walther LG 300 XT).
        Bitte teilen Sie mir vorher Ihren Preis mit.

        Danke Günter Bernheiden

      • Hallo Günter,

        Vielen Dank fur die anfrage. Ich werde Ihnen einen Email schicken.
        Mit Freundlichen Grüsse,

  12. Hi
    Wondered if you could help, I am looking for a quick fill with pressure gauge for my LG110. Can you help and how much would the fitting be with postage.

    • Hi Trevor,
      I have an expensive and a cheap solution:
      1. Buy an original Steyr cylinder with quick fill: for 255 Euro. Expensive but safe and sound
      2. Try your Czech language skills here: for about 70 Euro for the kit and about the same amount for installation.
      You would need to send your own cylinder to the Czech Republic from what I can make from it. This guy also does cylinder conversions for Walther, Walther! 😉 , Feinwerkbau, CZ200, Airarms e.g. so he seems to have a lot of experience. For the Steyr it means he has to modify the cylinder by cutting the original end off and cut new thread for his quick fill. Irreversible that means. For the Walther it would be reversible because he uses the original threading and does not change the cylinder.

      I modified my Steyr cylinder myself with a Best Fittings set. But you loose the gauge. I have opened the Steyr cylinder, removed the gauge and replaced it with a Foster male connector with valve . It’s not too complicated but you need the right tools. On the Steyr the gauge housing is an integral part of the cylinder. You cannot screw of the knurled section!

      Best option is of course to get rid off that Tiroler thing and stick with the Hun 🙂

  13. Hello, with the settings you provide on the site to reach the strength of the weapon up to 16, the possible number of possible shots from the reservoir pressure of 300 to 90 for walter lg 300 anatomic

    • Thank you for your question. I never fill my reservoir to 300 bar so I cannot tell you how many shots you can get from a 300 bar fill.
      I fill to 200 bar and I get 90 shots and then the pressure is 100 bar. Based on this I would say you get at least 180 shots from a 300 bar filled reservoir.

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