Venom used to sell the HW35 in FAC form at 15ftlbs
Norman May found that the HW35 would run at 15ftlbs when they were experimenting on operation Vixen.
To the best of my limited Knowledge on the HW35, all of them had a 30mm cylinder bore and about a 65mm piston stroke, and a 2.8mm transfer port diameter.
From my experiments I found that my 35 will run at 13.5 ftlbs in standard form (65mm stroke) when tuned.
I have now de-stroked this gun down to a 55mm stroke which gives 11.5 ftlbs, the mainspring in this gun has absolutely no preload prior to fitting the trigger housing.
The build quality of the HW35 for a gun designed in 1939 is unbelievable and apart from the breach shims, easy to strip and rebuild.
That's probably why they are still in production, and long may they live.
All the best Mick