Q. But aren't all M193 rounds the same? It's a standard specification, right?
Yes and no.
While several parameters are set out for bullet size shape and construction, there is still room for differences. The shape of the boat tail, the thickness of jackets and the type of cannelure all vary with manufacturers.
Types of powder, materials and manufacturing process will all contribute to the differing characteristics of one load or another. Additionally, variations between lots from the same manufacturer might depend on what materials were available at the time of manufacture or what the humidity in the plant was during manufacture.
The best way to decide on the type of M193 (or any ammo for that matter) you prefer is to make an educated guess based on feedback of AR15.com members and other sources before shooting some in the weapon of your choice to see how it performs.
Lake City '00 (left) and 1986 South African (right).
Lake City '00 (left) and 1986 South African (right). Note the difference in Cannelure and boat tail shape.