Is it legal to own a .50 caliber weapon in the uk?

If you have the correct firearms licence/certificate, would you be able to own a .50 caliber semi-automatic firearm in the uk? im asking because i was looking on a website because i was browsing a website for airguns but i saw that it sold firearms so i had a look and i found a .50 cal bolt action steyr rifle. it was on this website: http://www.sportsmanguncentre.co.uk/product/324c5c0bedee6d3259611998/STEYR+HS+-%7C50+M1/