Yes, I have tried them in a bullet. I gave up on both the bullet pen and Zebra ballpoint refills in favor of Space Pen refills in 301 compact pens. Both the Fisher & Zebra refills are 3-1/2 inches in length, so there is no "trimming" required to interchange them. The Fisher refill point is somewhat larger in diameter than the Zebra, so it won't fit a Zebra Pen without enlarging the opening very slightly, but Zebra into Fisher works without modification. I've had both the metal & plastic refills and had no issues with either. Unless there have been changes to the bullet pen (mine was purchased a long time ago in a pen store far, far away), I'm puzzled why it would not work.