For self defense only, not for target shooting. I researched them and tested them on a variety of targets. They are destroyed when they hit a hard surface, splitting in half at the point of contact. During my testing, it turned out that they were made to trap air very efficiently and propel an object down the barrel at exceptional speed. I don't have a crown so I can't check the exact velocity when exiting the barrel, but it's much faster than a regular round projectile. This hollow structure also makes the structure weak when hitting a hard surface, soft impacts make it reusable after washing and drying. They are not designed for magazine-fed weapons or magazine-fed devices. You have to manually insert it into the barrel and make sure it's seated properly. I tested my batch with the T4E Umarex HDS 16 Joule version (trimmed double barrel modified for more gas release) and they performed amazingly. As said, they are designed to protect themselves, don't waste them shooting paper or any hard surface. If you want to shoot hard objects, buy HARD balls. My only criticism of this product is the price, you should get triple the price or sell them for around $15. I can print them much cheaper with heavier material, which I will do.
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