If you don't mind using unjacketed bullets, you can buy lead ones ready to go

https://itlshootingsupplies.co.uk/pr...t-heads/page/3

Come to around 8p each.

ITL sell jacketed ones too - more expensive of course.

https://itlshootingsupplies.co.uk/pr...t-heads/page/2

He is usually at Kempton, but do check with him.