1000+ FPS 8mm Giffard HPA conversion

[Buxton]

The other day I fitted a telescopic sight to my 8mm Giffard for some accuracy

It was grouping at around 1" at 50 yards with home cast 8mm balls at around 1000fps

Groups much better at this velocity than it does on co2 at longer ranges.

[calvin moser]

I am a new member as of yesterday. This is my first attempt to communicate on this sight. As I purchased my 8 mm Giffard, without reconditioning co2 cartridge I am getting about 370 ft / second with a 3.15 round ball. instead of rebuilding the original cartridge I would like to leave original. I see there is a 8mm buxton conversion for my Giffard. I would be interested in plans, diagrams or kit all ready to go.
Thank you. Calvin Moser, South Dakota.