Originally Posted By DSZM4:
9310 material is used for a few reasons
It's sold in round stock and it can be hard turned. It also is a high nickle steel and can be chrome plated with less issues with breaking. Because of its high nickle content it is less brittle.
158 is the material that is Mil Spec and its as good as 9310 AS LONG AS the company buys alot of this steel because a company would have to buy a whole mill run of this to even be able to get some. This makes it tough for companies to buy it unless they plan on being a Colt size mil spec supplier/contractor.
158 Mil Spec which means 158 material is on the TDP but as soon as the next TDP holder submits this material change to 9310 the US Government will accept it, because there is not any durablity or function change.
158 is cheaper but 9310 can be purchased in lower amounts, which for most manufactures is even more important.
6 of 1 half dozen of anouther.
Who is the next TDP holder? Colt owns both TDPs (M16 and M4) and licenses them out.