dead to shoot domi

Discussion in 'Walther' started by hmangphilly, Jun 20, 2015.

  1. hmangphilly

    hmangphilly The Doctor

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    been shooting me domi again ....i missed it .

    just wondered is there any such thing as a dead to shoot domi ?

    as far as i know they all give a little nudge ......
     
  2. Neil

    Neil MFTA Winter League Champion 2011 and winner of som

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    All of mine did to varying degrees but I still loved them for ten years.
     
  3. NeilM

    NeilM Well-Known Member

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    The ones I shot in the past and more recently all have that nudge.

    I have never looked into why, but if it was a jetting effect, then a really good muzzle brake / stripper may be able to dissipate the air enough to reduce the effect.
     
  4. Ratinator

    Ratinator 77.74

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    My old dommi

    The dommi I owned developed a problem with the pin that runs through the hammer shaving bits of Ali from the slot that it ran in. I solved this by getting the slot machined out to accomadate a small roller bearing , this transformed the way that the gun shot.
    Mr D called it a Steyr Walther , coupled with a side venting shroud it would just have a slight backwards motion on firing.
     
  5. hmangphilly

    hmangphilly The Doctor

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    Interesting , thanks for that . I'm sure a lot of the movement is muzzle blast . The 16j hammer and spring are pretty chunky though. A
    Fair bit of mechanicals going on there.
    Saw your domi for sale around the time I decided I wanted one. Kicked myself at the time :(
     
  6. Ratinator

    Ratinator 77.74

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    Not sure where it is now

    The guy that bought it from me sold it to his mate so I lost track of it . It was a desperate measure to take but I could not see an alternative , it really did transform the firing cycle. The anodising had worn through and it caused me to have very inconsistent fps , if the pin dragged it was low on power . I think it's one area on the dommi that needs keeping a check on , not sure if a smear of grease would reduce wear. As for the muzzle mine seemed more aggressive with the ti pepper pot on .
     
  7. sven

    sven Member

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    Hi Phil,
    The dominator has a heavy hammer and spring. I don't know why Walther chose to use these because the lighter hammer and spring from the 10meter /7.5J version will do the job as well and cause less hammer bounce thus less jet effect. I have a converted LG300 and a Dommi. The converted LG300 has the light 10m hammer and spring and when I shoot it I find it has less shot reaction compared to the dommi.
    If you'd want less nudge than that the LG400 with the magnetic absorber has the least felt shot reaction of the Walther rifles. And the LG400 is a much lighter rifle compared to the dommie indicating that the technical differences really do their thing to reduce shot reaction. The hammer and valve are lighter than the LG300 and (probably because of that) the air consumption of the LG400 is lower. Indicating there is less jet effect in the LG400. And the magnetic absorber shaves off some more "nudge".

    So to get less nudge with the dommi you could try to achieve that by using the lighter hammer and spring from the 10m/7.5J LG300. This will reduce hammer bounce and jet effect. And maybe have a go with tuning the reg pressure (but I think you've already tried that in the past).
     
    Last edited: Jun 22, 2015
  8. RobF

    RobF Administrator Staff Member

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    Got my 300 XT running 6ft-lb phil we can play with... won't be missing paper with that till the winter at least so it's not getting any exercise...

    I need to get on that cradle for the action and then we can test kick with the widget... should have strapped it on yesterday but forgot...
     
  9. hmangphilly

    hmangphilly The Doctor

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    Ooh ooh , just had a mega idea about the mechanicals

    ,,watch this space .

    Cheers Sven that's interesting stuff . I might have some thing to help with what's left of your blast ...

    Rob this cradle thing . We might be overthinking it.
    How's about 3 fine delrin contact points on a flat surface like an old mirror ?
     
    Last edited: Jun 22, 2015
  10. RobF

    RobF Administrator Staff Member

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    We can give it a go... i've got something to support an action... just that free float that is consistent that we need...
     
  11. hmangphilly

    hmangphilly The Doctor

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    hey sven ,
    could you weigh your 10m hammer for me if you get a chance . i'm thinking of making a slimmed down version ....they're too dear to buy , and i'm too tight :)

    i'd be interested to see how that magnetic system works , i can see it's on the probe.

    as you know i've mucked about with smaller valves , port sizes and reg pressures , then i got a bit sidetracked...

    blast is certainly a major contributor to recoil in my domi ,and as neil m says, a muzzle brake makes a big difference....although the term recoil is a bit harsh for what i get.....i just think i can get it a bit closer to the level of where we're at with the steyr now ....which is pretty low recoil / shot reaction / blast/ jetting , call it.what you will .

    tell you what though i did have it shooting low recoil with a nice fitting delrin guide in the main spring ...then swapped it to a looser one 'cos i was afraid of temp variation never did actually check if it did vary .....i'll have to revisit that....i think i might have had a long valve / thin seat combination to effectively short stroke the hammer by a mm or 2 ....i'll check my notes

    sven what are you using at the muzzle ?
    is your barrel shrouded?
    what's your barrel diameter ?
     
    Last edited: Jun 23, 2015
  12. hmangphilly

    hmangphilly The Doctor

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    yes interesting to see what it registers with normal hold , and how altering the hold affects the shot reaction.

    that might be as pertinent as figures from an artificially supported rifle.

    them springers bounce about tho don't they ?.......blimey ....I'd forgotten all about that .......cant shoot 'em for toffee :(
     
  13. RobF

    RobF Administrator Staff Member

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    have a go with mine, it's pretty sweet now i think... we'll so far the pellets are roughly going where they should...

    now we have some nice weather my clients have decided to make me work :(
     
  14. sven

    sven Member

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    I put the answers in you r post:
    QUOTE=hmangphilly
    hey sven ,
    could you weigh your 10m hammer for me if you get a chance . i'm thinking of making a slimmed down version ....they're too dear to buy , and i'm too tight :)
    The LG300 hammer is 28 gram (From memory: dommi is 34 and the LG400 is 14 gram
    i'd be interested to see how that magnetic system works , i can see it's on the probe.
    [​IMG]
    When you look at the picture (this one from LG300 Pro Touch) it is a little confusing because the magnet (26) and the absorber mass (27) are pictured as two parts. In reality the magnet sits glued inside the mass. The magnet sticks to the probe (29) when you cock the rifle. When fired the impusle force releases the magnet+mass and the spring (24) pushes them to the rear. The amount of rearward movement can be adjusted by screw 34 that controls the air flow out of the hole behind the absorber mass.So there is no air used to move the absorber rearward. It is just the shot impulse that overcomes the magnetic force. The pellet probe is a solid piece with no porting for air. On the newer LG300 rifles the magnetic absorber can be retrofitted to replace the pneumatic type. The older dommi will not have a large enough chamber for the absorber system. But maybe the newer dominators are based on the LG300 breechblock that do have the larger chamber.

    as you know i've mucked about with smaller valves , port sizes and reg pressures , then i got a bit sidetracked...

    blast is certainly a major contributor to recoil in my domi ,and as neil m says, a muzzle brake makes a big difference....although the term recoil is a bit harsh for what i get.....i just think i can get it a bit closer to the level of where we're at with the steyr now ....which is pretty low recoil / shot reaction / blast/ jetting , call it.what you will .

    tell you what though i did have it shooting low recoil with a nice fitting delrin guide in the main spring ...then swapped it to a looser one 'cos i was afraid of temp variation never did actually check if it did vary .....i'll have to revisit that....i think i might have had a long valve / thin seat combination to effectively short stroke the hammer by a mm or 2 ....i'll check my notes

    sven what are you using at the muzzle ?
    I use a self made delrin moderater that fits inside the carbon shroud. https://airgunaccuracy.wordpress.co...sh-in-silencer-sound-moderator-for-the-lg400/ And on the 300 and 400 I use the original Walther muzzle weight/sight base

    is your barrel shrouded? Yes. I use the original barrel shroud combos on them.
    what's your barrel diameter ?I use the original barrels on my Dommi's , LG300 an LG400. I think these just a tad under 15mm with a shroud of 20mm O.D.
    Cheers, Sven.
     
    Last edited: Jun 24, 2015
  15. hmangphilly

    hmangphilly The Doctor

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    Thanks Sven

    Hammer specs gratefully received , I don't think I'll be going down from 34 to 14 grams with std domi valve but mid 20s might be a good place to start.
    I could prob drop thd weight if I used my 1.5 stem smaller head valve , we'll see .

    That magnet / stabiliser system is interesting .
    No room to build into std domi probe but got me thinking .

    Liking the mod , very tidy .
    Been messing with a similar project .
    And spookily 7mm outlet seems nice here too .

    How does yours affect the feel of the gun ?
    Mine seems to dampen it considerably , still fine tuning but positive noises from chief test pilot :):)
     
  16. hmangphilly

    hmangphilly The Doctor

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    well

    [​IMG]

    well it cocks and fires , trigger feels ok .

    std reg seems balanced at 84 bar so go with that at the moment
    std ...ish size and profile valve ....but the seat a bit deeper at 2.85 instead of 1.85
    std springs x 2
    larger reg reservoir cant remember the volume ... measure later

    my power peeks at 753 fps with 8.4s any spring adjustment either way and the fps goes down ,
    whassat just under 10 .6fpe.?....we'll see how it shoots but my head would like to get it to 780 ish

    i'll have a little muck about later, see if we can get her up there.

    it still nudges though :eek:o

    hope this don't turn into an epic project, i've got other stuff to do .......easily sidetracked that's me
     
    Last edited: Jun 25, 2015
  17. hmangphilly

    hmangphilly The Doctor

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    power's back

    fitted a std valve .....thanks rob :)
    std dimension seat 1.85 mm deep
    and a skinny little .43mm wire 5.4 x 16.5 mm spring

    had to turn it down actually so looks like i had too much return spring , sounds quite soft at 770 ...8.4s and 810...7.9s.
    lets see how she settles and feels after a few pellets soft at the mo but deffo not dead ...i dont think i'll get that without some kind of stabilizer arrangement......we'll see
     
  18. sven

    sven Member

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    Hi Phil,
    Nice work, making your own hammer.
    Would you say that the lighter hammer itself does not reduce the nudge?
    But that the lighter valve return spring in combination with the lighter hammer does reduce the nudge?

    You already have done a lot of work on the Walther so maybe you don't need this advise, but:
    In my opinion to reduce the nudge it is necessary to reduce the amount and/or pressure of the air that leaves the muzzle after the pellet (jet effect). The hammer bouncing and "valve open time" affect the amount of air that leaves the muzzle. I have seen data that shows the LG300 hammer bounces 4 times for every shot and that it is hard to reduce the number of bounces.
    Hammerspring pre tension, Valve return spring tension and Reg pressure are the factors here. It is difficult to tune those 3 three factors because they are interrelated. But in general I'd say:

    Try to go low on hammerspring tension. This is a sensitive setting. A quarter turn on the setscrew can make a big difference in bounce. Maybe even more so with a light hammer. You might want to start at a setting where the hammer is not under any spring pressure when the hammer is not cocked (1mm gap).
    Try to get the 11,5 fpe with the lowest hammerspring tension by adjusting the reg pressure (try 90, 95 and 100 bar) and valve return spring tension.
    Higher reg pressure may give shorter valve open time. The data I've seen showed that at the shot the pressure drop in the reg chamber is 20 to 35 bar depending on settings (with std. chamber volume). So there is still 50 to 65 bar pushing on the valve when the reg setting is on 85 bar. When the reg pressure increases to 95 bar the pressure left in the reg chamber will increase and push harder on the valve.
    And a lighter valve return spring and it's pre-tension (add washers in the reg cavity) may help as well.

    But the main thing to aim for in my humble opinion is the low hammerspring pre-tension. To get 11,5fpe at a low tension you'd probably need to increase reg pressure (or volume) and decrease valve return spring tension.
    Good luck and keep up the hard work :)
     
    Last edited: Jun 26, 2015
  19. Ratinator

    Ratinator 77.74

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    Effects

    A couple of thing that might help or may be of no use what so ever, you decide.
    First I did notice that the feel of my Walther changed when I fitted a silencer[muzzle blast] theory the other is something I tried no a Steyr.
    When having problems with power inconsistency I thought that maybe the valve not shutting fast enough was an issue ,so I made a very small top hat to fit the valve return spring.
    This would have increased the springs length by about .5 mm and the effect was not good.
    You could quite clearly feel how slammy the firing cycle became with the increased pressure on the valve, maybe a softer spring might help eliminate that.
    Simon
     
  20. Ceathreamhnan

    Ceathreamhnan WHFTA Champion 2013

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    The later of my two Dominator actions (serial 50874) has the wider cylindrical hole behind the pellet probe that could accommodate the stabilser. The 'skirt' of the probe is larger to fit in it.
     

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