Mortar Fireworks is a common search term, also known as reloadable mortar shells, actually the mortar is reloadable not the shell! This is a sometimes misused term in fireworks so let’s set the story 
straight. Shells, are the actual firework. Mortars, are the tube the shell is loaded into and fired from. Common, safe firework mortars may be made from cardboard, fiberglass or high density polyethylene (HDPE) depending on the strength of the shell to be launched. Cardboard is acceptable for some lower powered shells such as Festival Balls and Black Box artillery, however HDPE or fiberglass is almost always a better choice, and to take safety and your display up even another notch we recommend firing even consumer shells out of mortars in racks.
Firing shells form mortars in racks is how the pro’s do it, and for good reason. Mortar racks are more stable, and the fiberglass mortars, or tubes commonly used are far superior and less likely to blow out when using some of the more powerful conumer shells such as large cannister style shells.
These large cannister, or cylinder shells as they are sometimes referred to can legally contain up to 60g of total pyrotechnic composition making them the loudest legal firework available in the USA. Another big advantage to using a mortar rack is it gives you the ability to fuse multiple shells together, or load multiple shells for sequential firing without the danger of possibly reloading a shell into a mortar with burning embers in the bottom. For shell kits that are marked for effects it can e really fun to separate them and load them in such a way that you create your own color patterns in the sky!
