I recently bought a pair from "the bay", fitted one to a 35, after 5 days just sitting in the cupboard I went to use the rifle only to find the seal...
There was similar equipment on that site not too long ago, which I think the general consensus was that it was from the (then recently) defunct Lanes...
I have no personal experience of this model but, as Neil says, would guess that the swept volume may not be sufficient to achieve that sort of power...