Large Caliber Airguns

[Professor]

Does anyone know about people in the UK either shooting or building large caliber air rifles?

I was interested to discover that the Lewis and Clarke expedition in the pioneer days of North American exploration was at least partly armed with air rifles. They may have been .32 or .50 caliber, air reservoir types. Fans operate and build both muzzle and breach loading air rifles in the States, some of them using 300 foot pound specimens for hunting elk?

I'd be interested in any links to such activities in the UK, if anybody has them.

Thanks.