Depends on the springer, the most consistant springer I ever had, of which I did much of my various ammo testing (check out BB Bastards tests I did a bunch of years ago), I got the most accurate results between weights and brands from my TM Mk23 springer...... and I used it at games as well as a last resort backup, til I lost my mag at a game.....
Literally I'd get +/- 3fps from it, most consistant gun I own!