The lightest pellets I have ever seen are North Air CO2 PELL, (see pic below) The metal head is a tiny wadcutter, smaller than the normal Prometheus type seen also in the pic. My scale is down in the garage but I am guessing these are less than 5 grn. If you get in quick there is an original sealed packet of 400 at a shop in Scotland for £15.

Baz


https://i.imgur.com/v3zT5ae.jpg