Short stroking a Diana 52

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  • Short stroking a Diana 52

    Hi All,

    In my attempt to reduce the power of a Diana 52 from 17 to 7 fpe I decided to drastically shorten the spring (by some 75mm).

    The problem then is with a stroke of 100mm that the spring becomes coil bound & the gun won't cock.

    As 100mm stroke with a low powered spring would give a very lazy, firing cycle (= hold sensitive) I decided to short stroke the gun. This can be achieved normally by extending the piston head or the cocking rod.

    Short stroking reduces lock time, especially with very stiff springs.

    But thank the good lord for Airgun Forums, because a little tip was acquired. Luckily as the 52 has a transfer port concentric to the compression chamber another short stroking option is to make a plug with a hole in the centre. This is placed inside the compression tube & effectively reduces the guns swept volume.

    I reduced the stroke by 30mm & got near enough 7 fpe with Superdomes. And a sweet shooting, heavy, low recoiling springer is reborn.

    Cheers,

    Matt W

  • #2
    Attaboy Matt. I'm a bit hard of thinking this morning, so can you explain why it becomes coil-bound with a shorter spring? Was 100 mm the original stroke length?

    Comment


    • mattw975
      mattw975 commented
      Editing a comment
      Hi Riz,

      I'd cut so much off the spring that it was locking up at a fully compressed length of 80mm

      With a stroke of 100mm it ran out of travel before the trigger sear could engage & cock the rifle.

      Reducing the stroke to circa 70mm did the trick.

      Cheers,

      Matt W

  • #3
    Seems like it’s been a good weekend for chopping springs. I shortened a Webley spring last week for my HW35, but I reassembled the rifle yesterday and found that it wouldn’t cock. I didn’t have a lot of time but I stripped it down again and took another 1½ coils off. And it still wouldn’t cock. A bit of effing and blinding ensued, then I walked away to have a think…

    …and remembered that I’d set the trigger before reinstalling it (I find it easier that way) and forgot to un-set the bloody thing before trying to cock it.

    Embarrassing, but serves me right for rushing the job.

    Still, the upside is that it’s shooting nice and smoothly and giving about 9 fpe with superdomes, which I think is getting into the right sort of range for an untuned 35 in .177, especially with a dodgy breech lock.

    I’m still deciding how to tackle the breech lock, but I’m trying to ration myself to one balls-up a day so I put that decision off for later.

    Comment


    • sn@abrc
      [email protected] commented
      Editing a comment
      OK fellas, you have me both curious and intrigued.......

      Practically every kid [and "grownup" bloke] I have known with an air rifle has tried to uprate the power- I never even considered downrating as something done in Oz.

      Understandable in the UK or Europe where there are limits allowed before red tape applies.

      I cant think why I would cut the nuts off a damn good springer like my '52 diana, maybe an old cheapie being relegated to teaching youngsters or something like that.

      Dont get me wrong- not knocking what you are doing- just need educating on the whys and wherefores.

      [we need a head scratching smiley.....]

      stephen
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