Mortar explodes in a tube, HDPE vs Fiberglass, fired remotely

This video is for education purposes. It illustrates how dangerous it could be if you manage to put a shell in upside down in a tube or if one explodes due to a defect, and what would happens to both a HDPE and Fiberglass tube. Now, no one else has to do it to find out. All conditions were controlled with the usual safety gear. A brief set up then each tube is tested and then the results. As you can tell you should not be anywhere near them. The long delay in me going from where the camera is to a sheltered position to fire them. It is about 15 to 20 seconds.
Be safe and do not repeat this experiment despite the fact that these tubes work as designed. However, I would not use fiberglass tubes that do not have a wooden base in case you get a bad shell. You will see why. Even with HDPE you would not want to be too close either. You will see why.