Thread: ftp 900
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Old 18th October 2016, 05:33 PM
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Tench Tench is offline
WHFTA World Champion 2016.
Join Date: Sep 2009
Location: derby
Posts: 1,423

AA in their wisdom (?) don't use a gland seal on the firing valve stem, this causes air to leak down the valve stem when the transfer port is under pressure during the firing cycle. I think this hole also allows air to escape during the forward travel of the hammer. If this is the case blocking the hole will slow the hammer and reduce the power. Blocking the hole will also cause the air escaping down the valve stem to blow the hammer back causing a double (or more) tap on the valve, this is most likely what people hear when they say the sound of the gun changes. Basically it all comes down to a design that cuts corners, unfortunately loads of different makes of rifles are made without stem seals.

With the exception of BSA I cant think of another maker that uses valve stem seals on all their designs?
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