Airgun Accuracy

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Walther LG300 Dominator Tuning

There once was a Scottish airgun forum. This contained a lot of info on the Walther LG300 Dominator field target rifles. Unfortunately this forum disappeared a few years ago and together with it the valuable info on tuning and repairing the Walther LG300 Dominator.

I copied some text and picture parts of the forum in the past for later use and thought I would be handy to publish it here.

There are four parts:

  1. New here and being doing some work to my Walther lately
  2. Guide-pellet probe removal and reassembly
  3. Extended scope rail and barrel shroud removal
  4. Firing Valve

 

1.Post subject: New here and being doing some work to my Walther lately
I bought this dominator about 3 years ago used from a local gun shop. Right off the bat I knew I had reg. problems. I got the updated reg but it didn’t help. I kinda put it up for the past 3 years until recently.

I tore the reg apart did some machine work to it changed the configuration of the poppet valve and seat. I also made a new firing valve seat out of delrin. I am now getting a stdv of 2.1fps. I then added a pressure gauge so I can keep a check on the pressure of the reg. My air cylinder has had the pressure gauge removed and I added a quick fill fitting. The next thing was a barrel change I bought a HW barrel blank and machined it to fit. I am now shooting 18.5fpe. I am using CPH’s at 875fps. I changed scopes now to a Leupold 35×45 competition and just finished with the new elevation and AO knobs. My next project is a muzzle brake/stripper and I think I will be done.

The regulator. I milled the floating brass seat flat and made a new seat for the poppet out of Teflon. I then shortened the pin on the backside of the poppet that makes contact with piston to where there it only has .006 sticking past the floating seat. I also cut a new delrin seat to replace the firing valve seat. Once I was done and testing it I sat the gun outside and let it get it get downn to 30deg and shot it over the chrony and had no change in the velocity, I then warmed the gun up to 90 deg and still had no change in velocity. I also free floated the barrel.

What pressure do you set it at for 18.5 ft lbs? 1650psi

My own dommie has the revised regulator and so far it’s been behaving itself. I adjusted the hammer preload when I first got it (it was running a little too hot) and found that the first couple of turns on the hammer spring made no difference to the velocity, just the muzzle report! Further adjustment finally caused the velocity to drop. After some initial running in and minor re-adjustment, it’s been running at the same MV ever since.

I went all the way through the reg. I figured out that at 1700 psi there was 220psi being exerted on the belleville stack piston went through and measured and figured out which belleville washers were in there. I thought about changing them but as it turns out for that size piston there are the perfect size for the amount of deflection and compression force. Just a note to anyone that takes there’s apart and happens to drop the stack and have to restack them they are stacked 3×3 here is the best I can show you ((()))((()))((()))((()))((( and if I remember right there is a total of 27 of them. With the compression force of each mathmatically it makes more sense for them to stacked 2×2 but I tried it no go.

Here is a post on the “yellow” with my shot string graphed out.http://www.network54.com/Forum/79537/message/1237146819/How+much+recoil+do+you+feel+with+your+PCP%27s+shooting+at+18-20+fpe

Shot string over 67 shots

Shot string over 67 shots

The specs for the regulator says it’s set for 1450 for the 27 joule, 1160 for others. I was thinking bumping it up would up the maximum fpe you could get.

One of the best things I have read on the forums was tune the gun to where it wants to be and works well, not where you want it.

I started out with it lower, I had to bump it up when I went with the 24″ HW barrel. The alternative was to make a extension for the air resevoir. I kept making small adjustments to the reg pressure and hammer spring and graphing them with a trend line I could see if I was trending up or down and also look at my STDV, and ES and shot count. I found when I had the pressure lower I was having a larger STDV around 4. I bumped up the reg pressure and got it down to 2.1 or so, then I started on the hammer spring because I was slowly trending up in FPS over the a 60 shot string it was only about 4 fps but I wanted it flat. I am kinda picky when I am doing this stuff.

2. Post subject: Guide-pellet probe removal and reassembly
How to remove and reassemble the pellet probe for the walther lg300 dominator.
The content here is based on the pictures and explanation kindly provided by -=ed in his earlier thread. The pictures are linked into this thread for ease of reference.
Disclaimer: No responsibility, liability or any other kind of bilities will be accepted for mishaps, consequences or bad stuff that may arise from the use, misuse, abuse, etc of the information presented. Use this information entirely at your own risk!

1

Unscrew cocking lever retaining screw and remove the cocking lever, associated levers and your spectacles…

2

A closer look at the cocking handle and associated levers.

A closer look at the cocking handle and associated levers.

A closer look at the cocking handle and associated levers.

 

5

Hold the pellet probe with a hex key against the spring pressure to remove the pin.

7

Loading probe and levers removed

A closer look at the pellet probe, the pin and return spring. Note hole on underside of pellet probe.

A closer look at the pellet probe, the pin and return spring. Note hole on underside of pellet probe.

8

To reassemble push the pellet probe (with spring and end cap attached) into the action.

9

Once far enough forward the pin can be re-installed.

10

Re-install levers…

11

Re-install levers… part 2

12

Complete by refitting the cocking lever and it’s retaining screw.

Norman Allen: I performed this partial strip after getting caught in heavy rain during a competition. On getting home, the cocking lever felt a bit ‘gritty’. I stripped down as suggested and cleaned off the parts. I reassembled, noting the necessity of manually pushing the probe forward with an allen key to be able to engage that particular lever with the cocking arm. It may sound a bit daft, but what lubrication (if any) would you use on the various contact points? At the moment I’ve spread minute quantities of 3-in-one oil onto the contact points, but am open to any suggestions. Many thanks for a superb section…keep it up! Cheers, Norman
ed: I use a teflon-based instrument oil, removeing any seepage with a q-tip.

3.Post subject: Extended scope rail and barrel shroud removal : How do you do it?

Scooby:
-Remove cylinder & Reg
-undo the three barrel screws & pull out the barrel
-Pull the remaining square rail extension off, this will leave two pins in the action
-Remove the pins with pliers, if you leabe the reg on you will mark it when pulling these pins
-You now have to heat the barrel shroud up to melt the thread lock
-Once it smokes it should pull off.
Be careful how you cool the barrel to prevent bending
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How would you heat the barrel to reduce the possibility of a disaster?
_________________
If you can rent or borrow a “heat gun”, the kind that is used for removing paint ( a hair dryer on steroids ), it should work. Regards, Bill
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Unfortunately it’s a blow torch job. I stick the breech end in the lathe, set it on the slowest speed then slowly play the flame over the shroud until the thread lock smokes, it’s then just a case of sticking a screwdriver into the shroud slots & pulling it off. I usually leave the barrel to completely cool before removing it. Before I had the lathe I also did a few by holding them in a work mate. The main thing is not to put the hot barrel on a cold surface or cool under running water, let it cool naturally.
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Thanks alot for that info. Sounds like it needs alot of heat. I’ve heard someone say that heat doesn’t work on a few dommie shrouds – they have to be machined off in a lathe.
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Have just removed the shroud from barrel. First tried scarey amounts heat but that didn’t loosen it so it was machined down until it was paper thin and then peeled off like foil. Anyone got any ideas how the remaining glue could be removed without being scraped or burnt?
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Depends on the type of adhesive, acetone will deal with most stuff, cured epoxy may need a caustic solution. Cyanalites (super glue) has a softener, the name of which escapes me. Edit: I forgot to mention, if it’s some kind of acrilic, then ether is the solvent of choice, just don’t go to sleep on the job
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Numb Nut: I’ve already tried acetone, MEK, cellulose thinners and paint stripper – these had no effect.
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It sounds like it’s cured epoxy, which just leaves a caustic solution or mechanical means. Caustic soda is nasty stuff!
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Numb Nut: Thanks for the idea s10. Just tried drain cleaner on the barrel, let it to soak in for about 15 mins, it had no effect on the glue. I’ve used this same product to remove anodising from alu so it’s decent strength I believe.
________________________________________
Scooby: Stick it back in the Lathe & use emery paper to get it off, finish the barrel with a fine grade & it doesn’t even need shrouding to cover it up, just keep it well oiled & it won’t rust
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Numb Nut: Thanks for the emery paper idea – I’m keeping that as the last option – was tempted to start scraping away at the glue with a blade but keep thinking that something should be able to get rid of the glue without getting too medieval. It’s proving to be a challenge!
Talking of shrouds – am tempted to make a shroud from 20mm alu tube. Quite fancy a shroud that will quieten the muzzle crack down – a bit like the MFR or the daystate mk4 shrouds (but made without any complicated screw threading!). Need to find some pics of the baffles and see how easy they look to make. If in the end it turns out to affect accuracy then I can maybe cut some holes and fit an adjustable cone…
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Numb Nut: I got a prompt reply from walther informing me that the glue is loctite 638. In theory this should breakdown with methylene chloride, the main ingredient in the paint stripper I was using earlier, so I retried it, leaving it for several hours and used a bronze wire brush to scrub on it. After a couple of applications most of the glue was gone so I finished it by giving it a good rinse under the tap, polished it up with scotchbrite and then wiped with oil. The barrel now looks quite presentable, very shiney! Next step is to make a shroud using some Alu tube bought from ebay (17mm ID, 20mm OD, 500mm long). Hoping to try using some baffles to reduce the muzzle report. Looking for advice on what sort of baffles to use – the shroud will extend 50mm infront of the barrel, so might be able to get some decent noise reduction…

4. Post Subject: Firing Valve

It’s been quiet on here lately so thought I’d post a pic of the firing valve in my walther dominator. I think there are a couple of versions of valve – anyone happen to know the details? Which one is mine?
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Was just wondering if the valve pictured was a flat or tapered valve – wasn’t sure if the description applied to the front face of the valve or the sides. Isn’t one of the valve designs supposed to be problematic? Anyone know the details?
Incidently, in the above pic the valve is poking out of the regulator, so the sealing face is the top surface.
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That one is the later flat valve ,the early taper seat one has a green seal and has problems with temp shift as it gets colder the seal material gets harder and the speed goes up.
Don Old
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There are two types of white ones ,std walther ptfe type and the harder Nick M ones which are nylon.
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Thanks alot for that useful info, Villiers! This seal in this rifle is made from white plastic seal. I took a picture of it but it didn’t come out too good – unable to see the contours that are in the seal. Sounds like I can count myself lucky that I have the revised good valve.
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Just thought I’d update this thread to say that my Walther has started playing up – the chrono showed a rather high shot to shot variation and a low muzzle velocity. I adjusted the velocity back up a while ago (with hammer spring adjuster) but it’s dropped again.
It seems the problem is the factory standard exhaust valve seat – mine has a white PTFE seat. Appears this is soft enough to distort with the impact of the valve snapping shut after a few thousand shots. This has caused the metal valve to make a recess into the plastic material and requires the valve to be hit harder to open far enough past the edges of the recess in the plastic to get a decent blast of air down the barrel…
Looking forward to get a replacement valve seat from Nick soon – I understand that they are made from Delrin. Anyone else had this problem with the factory standard white plastic seal?

3 thoughts on “Walther LG300 Dominator Tuning

  1. what about the valve spring! i use the standart 6 lib spring with a 15 lib regulator and have many problems!extreme spread over 30 feet from 200 to 111 bars with 8.44 jsbs!!

    • Hello Kakos,
      30 feet per second E.S. is too much. But I doubt if the valve return spring (VRS) is the problem. The valve return spring is the same for all LG300 and even the LG400 models. There is no difference in valve return springs between 6 or 12 fpe (footpound) rifles. I have read somewhere that the LGM or LGM-2 rifles have a weaker VRS compared to the LG300 but apart from that they all have the same VRS.
      My guess would be to check the hammer and hammerspring. Clean away all oil or grease and run it completely dry. If still not okay check the pressure regulator with a regulator tester.
      Good luck with your repairs,
      Sven

  2. hi Sven ,if you ask Walther or Judith will give you different VRS for 6,12, 16 lib LG300 !the code of the spare is the same but
    there are differences in length!

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