Induced at 38 weeks

Hi mummies, i already been admitted today and has been induced at 11.05am but this time with bullet types. My no 4 pregnancy. I have to wait for 2 hrs they will check again. Previously my no 3 child at 2018 was not bullet. But it takes so long my cervix to open till tomorrow still 2cm. But i feel the contractions so worse. Endup been transferred to delivery suite for laughing gas. Anyone knows does the bullet is much better to open cervix faster or what's the different?