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Thread: crosman 140 replacement piston head

  1. #1
    Join Date
    Dec 2016
    Location
    leeds
    Posts
    2,099

    crosman 140 replacement piston head

    I was asked about a replacement piston head for a 140 and as in the UK we have a power limit and sadly the 140 in std form is capable of exceeding it I convert mine to a pressure blow off piston (this is for a non UK gun)
    this leaves me with a few std pistons so I set about converting one to an o ring
    first I removed the old seal(carefully milling the brass collar in two places to leave the old seal intact so I cam possibly replicate it at a future date) and the washer and felt wiper
    I then machined the piston a bit shorter and altered the felt wiper location to take a different size piece of felt
    I then threaded the pistom m8 and drilled and tapped a piece of brass m8
    the two pieces were screwed together and then the final machining and o ring groove was cut to keep everything as concentric to the piston rod as possible
    i could have replaced all the head and made a full brass one but this way enabled me to keep the felt wiper
    https://i.imgur.com/dh9IHNC.jpg

  2. #2
    Join Date
    Mar 2011
    Location
    Macclesfield and Ely
    Posts
    1,073

    Blow off

    I think I have one of your pistons in my 140 it has Belleville washers and a spring ball bearing set up.

  3. #3
    Join Date
    Dec 2016
    Location
    leeds
    Posts
    2,099
    it's based on my design but I didn't make it as I allowed someone to borrow one so he could make one for himself and I believe he later sold you the gun
    I use coil springs rather than Belleville's thje ball and seal I supplied though so if you ever need a replacement I can make you one

  4. #4
    Join Date
    Mar 2011
    Location
    Macclesfield and Ely
    Posts
    1,073

    Non working

    It doesn't really work very well as it never blows off and I can't be bothered to spend hours setting up.
    The gun doesn't go over limit anyway.
    Cheers for that.

  5. #5
    Join Date
    Dec 2016
    Location
    leeds
    Posts
    2,099
    if your 140 doesn't go over 12 then it's either working and you don't realise it or it needs re sealing
    on mine I set them to blow off at around 7-8fpe as I don't often shoot them and wouldn't pump to full power if I did so

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