A lipstick bullet can hold firmly when pulled straight out and still slip when twisted. The two tests load the joint between the bullet and cup in different directions. Use both when that joint needs to resist axial movement and rotation.
Hold the cup, then load the bullet
Use representative bullets and cups assembled with the intended filling or insertion process. Record conditioning time and temperature. For a pull test, fix the cup without squeezing it out of shape, grip the bullet consistently, and apply load along its axis. Record the load at the agreed event, such as first movement or full separation. Note whether the bullet came out at the cup interface or fractured within the formula.
For the twist test, secure the cup and turn the bullet relative to it at a controlled rate. Record the torque at the first relative movement or fracture and describe the outcome. If the cup is installed in the mechanism, make sure the mechanism cannot turn with it or absorb part of the motion. The torque required to raise the bullet during normal operation answers a separate question about the mechanism.
Test pull and twist on separate specimens so the first test does not weaken the joint before the second. A soft formula can be damaged by a grip before the joint moves. Report those events explicitly and adjust the fixture if it is introducing the failure. Compare results by direction, conditioning, and failure location. A retention limit should come from the specific package and formula requirements. The SamBound packaging catalog is available at sambound.com.
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