Our carbide expansion bullet is engineered for precision and durability. With a polished or coated surface, it delivers outstanding performance in expanding copper, aluminum, or stainless steel tubes. Compatible with various expanding macOur carbide expansion bullet is engineered for precision and durability. With a polished or coated surface, it delivers outstanding performance in expanding copper, aluminum, or stainless steel tubes. Compatible with various expanding machines, it’s the ideal tool for industries such as air conditioning, automotive AC, heat pumps, and more.hines, it’s the ideal tool for industries such as air conditioning, automotive AC, heat pumps, and more.