This is mainly directed to Bigtoe & TonyL, & There excellent work on swept volume & Transfer ports !

Having a sort out today, I came accross a number of cylinder end caps with their various transfer ports,
I'lll start with the HW35 leaking problem ?
There is nothing wrong with the design of attaching them to the cylinder IE by Brazing, The problem is the operator,

I thought I would bore you a little with the problem & Answer,
Brazing is by the use of melted Brass as the medium, Brass is a combination of Copper & Zinc in various quantities,
Lets take a typical 60/40 ( Copper & Zinc )
The parts to be joined are heated , A Flux added & The lower melting brass ( In this mix Copper around 1060 C & Zinc around 420 ) Is added to the heated parts ,

These parts need a small gap for the liquid brass to enter ? I mention this as the adhesion betwix the adjoining parts is by the forming of a cohesive bond ( Thats stuck on to you Ha ha, )
Now soft Solder ( Thats Lead & tin ) Again lets say, Around 60/40 respectively, Works in a completely different way ? It needs small gaps between the parts to be joined & Capillary action ensures the fluxed liquid solder creeps along the adjoining parts ensuring a complete seal at a lower temperature,

A number of guns have the end of the cylinders sealed by Lead/Tin solder & work very well, ( Mainly Relum & Their counterparts )

To go back to the Brazed joint ?
The problem is Flux/Temperature/Flame , If overheated the Zinc in the brass will change from a Solid to a Liquid, To a Gas,
The joint is being overheated, The Zinc in the brass is volatizing, forming gas bubbles in the joint, Hence the leak,
The not overheated ones are fine !!!!!

A Brazed joint needs to be " Just " Enough heat, The use of a flux ensures adhesion &&&&& A Silica type layer over the molten metal to avoid the volatized Zinc from leaving ( In the form of a gas )
Furthermore , A slightly Oxidising flame is used when Welding or Brazing Brass for the same purpose " Not many people know that " Ha ha,

If I wanted to reduce transfer port size, I would remove the end cap,
Countersink it from the inside & Make a piston with a point ,
( Ala the early Airsporter ) This would virtually eliminate the transfer port size , PS Soft solder it on ?

Its time for my medication now ! A large whisky Ha ha, Ged.