I heard that there are some very accurate BB rifle, I don't shoot one and someone else will chime in and provide more details I think.
For non lead pellets, you actually have lots of choices now a days as many countries limit the use of lead for hunting... I think you can check out the pellets with 'green', 'non lead', 'hyper speed', 'light weight'.... They should be all without lead in it.
To my experience, non lead pellets usually could be a bit less accurate as material (alloy without lead inside) is much harder than lead, and weight usually 20+% less than lead pellets, not a good choice for springer, should be good on co2 (power usually weaker) or PCP (power adjustable), they flies faster, much greater penetration ability, won't deform when hitting hard objects... You will know when you start using it~
The Polymag below is lead pellet , the others not.


