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Forums Springers, Pumpers, C02, & Vintage HW55M Question Reply To: HW55M Question

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MDriskill
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Probably 1967 on your HW 35.

Leather seals last basically forever with even the most basic maintenance, and like everything else on the HW 55 was carefully designed and fitted for maximum smoothness and accuracy; Weihrauch kept the leather seal on the 55 long after they had converted all their sporters to plastic. Plastic piston seals, in my opinion, have little inherent advantage in lower-powered guns like the 55, though many will disagree! Your 35 would originally have had leather too, by the way, HW changed the 35 to plastic in the 850000 serial range IIRC.

The piston seal will be a cup shape with a hard rubber filler in the center, through which the seal’s attachment screw passes. If it looks good with no tears or divots and fits fairly snugly, it’s good.

All that being said, I’ve converted a couple of older 55’s with trashed seals to plastic, and that works fine too. The HW 55 uses the same 25mm seal as the HW 30/R7 design. I think JG Airguns sells those, maybe also Vortek or Maccari, haven’t looked in a while!

When doing a rebuild, I like to use 25-weight pure silicone oil (a good source is the shock absorber oil made for radio-control model cars). Soak the seal in silicone overnight, then dry up the excess (stand the piston on a paper towel for a few hours) and put some moly grease on the outside of the seal. Note, silicone is the best leather-to-metal lube, but TERRIBLE for metal-to-metal contact – soaking up the excess is important to keep it from migrating.

A leather seal will need a drop or two of oil once or twice a year. For that I use the old Beeman Chamber Oil (a stiff mixture of silicone + some neatsfoot oil I think) or Beeman Ultra Lube (same with some moly powder added), applied with a needle through the transfer port.