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Tuning Walther LP53 Tune

I first came up with the idea to tune the LP53 back in the 80s, simply because i loved the look of the gun, being similar to the simple lines of .22 target pistols of the 60s. No space commando plastic, or mock features but struggling to achieve much better than 415fps in stock spec.

I discovered the gun has quite ideal build parameters, of a relatively short TP which is in line with the cylinder and nice 23mm piston chamber of 46mm stroke. The problem was Walthers idea to place a small mainspring within the outer spring, presumably to get the most out of the relatively short stroke. Big mistake. It may have seemed like a good idea back in 1953 but an inner spring acting as an inner guide rod is just about the worst surface you could imagine for the efficient release of the outer spring, while the inner spring power actually adds very little in reality.

Chucking the original spring set out, I found that the HW30 spring to b a perfect fit inside the piston, with approx 0.7mm clearance (0.3mm once cocked) being about perfect and no need of sleeving. However, the inner guide is then too small to support this single spring as it was designed to fit the small inner spring of the Original spring set. Simple answer was to turn up a Delrin spring guide set to place over the existing guide and a top hat to place over the piston head unit. Tolerances were kept tight to minimise slop but allow free spin of the guide set on the existing guides and in so doing, removes all felt torque. Spring Twang, excessive with the stock spring set, is completely eliminated.

Results seem to return in the region of 70 fps to 100 fps dependent on piston head condition and much smoother performance.

Next, I designed a new piston head and reduced the TP to 3mm.
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Cloudshe...sadly not as I am one of the few on here who is on British soil....However, if you need sizes to get the parts made up, I can supply.

The mainspring is an easy task if you need the instructions. Failing all this, you could get a kit shipped from Proteks, which followed my original design to some extent. It just needs a better mainspring, namely a HW35 spring, chopped to 18 coils and flattened on its cut end.

The main problem with the LP53 is seeking out a piston seal and getting it shipped. Its worth pursuing however, as a tuned specimen is one of the best pistols in the world once sorted...
 
Hey @steveoo, very much appreciate you sharing your work and research. Ever been inside a Predom-Lucznik LP 53 clone? Obviously the user interface is inferior but wondering if the power plant has any potential and how truly bad the trigger might be. If I start experimenting there is a chance of total destruction and I don't want it to happen to my Walther.

Thanks
 

cloudshe

Member
Dec 5, 2020
7
0
Maryland
    Steveoo, you are to be commended for your help! here's something i got fm the TR Robb website TRROBB.COM that i thought i might give a try (they also sell the mainspring set but are OOS):


    Walther LP 53 Air Pistol PTFE Piston Head Assembly


    Walther LP 53 Air Pistol Piston Head assembly to replace the old inconsistent leather one. Fits the same as the old one, offset key hole type. I have tried to make these with less slop than the standard one as this can lose power. I have made them with a little more swept volume than the standard so with low friction they should help power and consistency. The Centre is included and now made of Stainless Steel.
    I have fitted this washer to an old LP 53 and I am very surprised at the difference. It now splits or goes through the top of a pellet tin after tuning and fitting the washer (depending on Pellet). We did not alter any of the ports but just fitted the Washer conversion and lubricated it correctly. It is now much more consistent and accurate.
     
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    I did not go the TR Robb route with his PTFE seal but you can. It gives about 500 fps when used in conjunction with my kit above, or about 40 fps over the stock Walther seal, but like all guns which use the PTFE head (Webley Tempest etc) there is too much slam because the seal eventually takes a set and is very temp sensitive. You can learn to shoot with the slam and temperature sensitivity of PTFE but it takes lots of practice. I simply found my own seal design can factor out the issues. Despite being a pistol marksman, I never got past the shifted group elevation of a Tempest, or Premier going from a Cold day to a warm one.

    The route i went here is placing the rubber buffer unit within the Leather seal (sitting just proud) The Stock Walther seal placed the rubber buffer ahead of the leather which created lost stroke. Placing the buffer inside the leather seal, gave me 2mm more stroke, giving me 45 fps. The rubber buffer (as a material) was something Walther did get right, It does not expand the leather, unlike leather buffers which slowly deform the outer seal outwards until it gets too tight.

    Forget more powerful springs, packing washers etc, the way to improve springer pistols is increasing the stroke, smoothing out the spring and reducing the TP diameter. All springer pistols benefit from having a TP not greater than 3mm. It just depends how difficult the reduction is for the 20fps gain and reduction in slam. While a well set up leather seal, like above, is hard to beat in a pistol. A lovely cushioned shot cycle and will last for years.

    The Predom, can be modified similarly but I never fell in love with the gun enough to want to bother. The huge effort with the LP53 came about because i liked the gun.
     

    cloudshe

    Member
    Dec 5, 2020
    7
    0
    Maryland
      Steveoo, pls excuse the excitement! pistol finally arrived, i was expecting it to be pretty rough fm the pictures, but it seems pretty solid. s/n 001158 so 1953 early model i guess.

      seller said he couldn't get it to shoot although it cocked (with only moderate effort) and recoiled and made appropriate sounds. i found the breech seal pretty flat and the inner mainspring in two pieces. i have not pulled the piston out yet, trying to make sure beforehand that i'll be able to get it back together. also, grips are missing, but am optimistic about finding parts and getting it in shooting condition!

      looks like JG Airguns has the seals (if going leather), grips (though only in black), replica cocking gadget, but no springs. i like your mod, maybe go with the Protec spring and see if i can get to the current leather seal, try your improvements

      so thanks for the great info, if there's anything you would like to suggest, i would be most grateful again for your help!

      cloudshe, Grasonville MD USA
       
      Ok....The thing I would do, is get hold of a HW30 mainspring and crop it to 18 coils, then close the last coil flat with a blow torch. Easier than it sounds.

      Then get a guide rod made with a 8.2mm hole drilled through it to fit over the stock guide. Failing this order the Proteks kit, chucking out the spring and replacing it with the HW30 spring as described above. Some wasted cost here but worth it and will last forever.

      The key with any springer pistol is to get the velocity upto the magical 500 fps mark, which sees the pellet leave the barrel before the recoil starts and then not affecting the pellet flight. 

      Grips maybe a problem. I have never seen any available. 
       

      cloudshe

      Member
      Dec 5, 2020
      7
      0
      Maryland
        hi again Steveoo

        got the LP53, knew it needed some work as the seller claimed it cocked & cycled but had been unable to shoot the pellet.

        i found the piston head keyhole area had failed along the inner perimeter and that piece, and the piston head, were missing, leaving the remnants of the leather seal in the exhaust port area. both springs had fractured and were in pieces. otherwise the pistol looked pretty solid for a 1953 sn. so $200 in parts, new piston & head w/seal and the Protek spring assy plus new grips & screws.

        i thought i had put plenty of pellgunoil on the new dry seal, but only got one pellet out then pffffft no pellet. after a bunch of trial and error and more pellgunoil down the port, the pellets are coming out regularly now (!) tho the accuracy with some cheapo daisy & crosman pellets is not great so far. i will try your pellet recommendations and am also thinking about the HW30 spring thing tho i don't have immediate access to a blow touch.

        can you give me any advice on oiling the leather seal? what to use, how much and when? 

        thanks! you've been a big help!
         
        If you have gone for a leather seal like mine above, you need to soak it in Neatsfoot oil. Its intended for leather, will not rot the leather and as a bonus, does not diesel.

        Look down inside the piston chamber and make sure the TP is clear. Clean out the chamber until it has a bright finish. I polished mine out using a 22.95 piece of turned Delrin with Auto sol on it. It gave me a perfectly true,,polished bore of 23mm. I then cleaned this out with bore cleaner.

        The piston was then polished in the lathe. The inside of the piston is clean enough and just needs a clean. Seal is assembled after 24 hrs in the oil. However, before i soaked the seal i put the seal on its key hole mounting unit and put it into a drill chuck, polishing the seal with wet and dry paper, until a nice slip fit was achieved into the piston chamber. Then i soaked it. It did not expand during the soaking as it is quite a hard leather...maybe growing .004 max. You need to get your piston sliding up and down nicely anyhow. A touch of Moly to the rear bearing of the piston is all that is needed. The odd drop of Neatsfoot down the TP will look after the seal.

        Mainspring and guides set can then be added. No need for grease, as the Delrin handles the bearing but i wiped a meniscus of oil to the outer of the spring where it contacts the piston.

        The use of the Falcon, or AA Express pellet is quite vital for the pistol has a tight bore. The rifling is perhaps the finest of any air pistol but it is a touch tight. Make sure the O ring is not worn flat. You want a 6mm bore O ring with 2mm cross section. Any bog std nitrile O ring is fine. It is the easiest sealing set up i have ever come across on any pistol, 100 percent reliable for 10, 000 shots and is a perfect hermetic seal.

        Clean the barrel and away you go. 

        There is a big benefit to a TP reduction on this model but we will deal with that at a later date. 


         

        cloudshe

        Member
        Dec 5, 2020
        7
        0
        Maryland
          thanks again, steveoo

          initially i've doused the seal with pellgunoil. i'll have to look for some neatsfoot oil, should be easy to find. the repro leather seal head assy sold by JG looks a little different, there's no rubber bumper, the washer holding the seal is recessed into the cup, and the screw is a phillips head and maybe a bit shorter than the one in your picture

          the cocking effort with the Protek spring is a bit strong, and there's a definite kick upon firing. i'm interested in the HW30 spring, can the ends be flattened using a regular workshop propane torch? grinding and polishing the ends should be no problem for me

          the accuracy of your '53 is impressive! got some Meister pellets on order, the ones i've been using have not been very accurate, maybe more break-in is needed. if you have the time, i would appreciate your info on getting the TP set up. 

          am considering getting another LP53 as mine might be a little over-the-hill. it looks solid but because of the wear/damage to the springs, piston, grips etc i wonder if the barrel might be suffering

          muchas gracias for sharing your expertise! 

          cloudshe
           
          Yeah the 30 spring, which is the best spring you will find for this gun and a nice fit in the piston, without needing to sleeve. Practically indestructible. Cut it to 19 coils then heat the end and flatten it until you get 18 to 18.5 coils. The latest idea is to not quench, presumably to reduce the chance of making the spring end too brittle, but i have always quenched in oil. I have never had one break. Might be a hair-brain idea to not quench...too slow cooling and you might lose the temper, but do not quench in water...too fast and the spring will crack at the base.

          Once flat, grind and polish the ends. Then remove all burrs inside the spring at this point, or they will cut into the delrin guide.

          It sounds like you using wrong pellets, not sealing at breech, or piston seal to get slam like that. Get it running right you will get hardly any.

          TP reduction is 2.8mm improves shot cycle no end and raises power but get the rest running right first.

          The 53 requires great care and attention to get right but it rewards massive when done. Treat it as if doing an antique clock re-fit....I didnt know wether to laugh, or cry when Mileski ran his AGW magazine tune of this gun. There are crud tune parts and expert tuners!