Recently I have been having a bit of a mess about with a Webley Hurricane and a couple of Tempests.
I wanted to get a piston lightened (cannot understand why a Mk1 pistol has a piston weighting about 67 grams and the Tempest / Hurricane 83? g as they seem to use generic mainsprings now).
The piston was lightened but the bore for the mainspring was also deepened a bit. A very kind chap off here did the piston for me, drilled and tapped it for a 2BA screw, supplied some Ptfe piston washers and "power washers" and also made up some piston weights with a thin flange so they would not add much preload to the mainspring.
I had brief use of a chronograph before it expired, actually dying of natural causes, rather than me killing it!
The Ptfe piston washer did not have a split in like the standard one and I found that the tightness of the screw seemed to make a lot of difference. I also found that they needed about 15 shots to warm up. With marksmen pellets, I was getting readings of 3.9 -4.2 ft lb and the odd ones a bit higher.
I discovered that some cylinders have a slight tight spot about 3mm from the end and asked troubled shooter about the construction. Somebody also cut open a corroded gun and found that there is a steel washer about 1/16 of an inch thick that goes into lip at the end of the cylinder and is crimped over. The cylinders were supposed to be honed afterwards. Ive got 2 pistols with the slight tightness and 1 without.
Anyhow, I wasnt happy with the Ptfe washers and tried to make a leather cup one that sealed well but sapped power. After the chronograph died, i was just shooting at a bit of cardboard with a steel backstop, so no real way of measuring.
One pistol had another washer made with a thinner "cup" and a bigger diameter centre-----------and the other a solid leather washer that has had a washer tightened down do form a shallow recess. A plastic disc has been cut from a milk bottle to go over the steel washer in this and also the other leather cup washer.
At various times, combinations of 2 mainsprings , a long (36 coils?) one and a shorter shiny one were tried. Also 3 different piston weights of 10/15 and 20 grams were tried and also "power washers"
At the and of it, the Hurricane has the lightened, deeper piston, a thin wall leather cup washer, the long mainspring and No (NO!) piston weight or power washer.
I dont know the power but the accuracy is great. Even at plinking speeds, it is very easy to get bottle cap sized groups at 7 1/2 - 8 yards shooting 2 handed. (I was even doing that without the grips on)
I think maybe the mainspring could do with a coil off , but I'm not cutting it yet as another piston is getting the bore done slightly deeper, to go on another pistol.
I had to cut down a guideto try the piston wieghts as I couldnt scrounge one that was already cut. You need to cut the guide or the piston weights with touch it and the gun wont cock. I've refitted the standard guide now.
So there you go if you fancy a tinker
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