This thead is old, but subject came up on several boards. This is Speer's response to the Lee comment on their die on Speer's website.
I bought a reloading die set and there’s a note with the dies that says something like, “Speer does not recommend using their bullets with these dies.” What’s the deal?
Speer never made such a broad recommendation. Speer’s recommendation is: Do not apply a crimp to any bullet that does not have a crimp groove. The die company in question markets a die to produce a “factory crimp” and recommends it be used on any bullet. Speer’s tests, and those by another bullet maker and an independent gun writer, show that crimping a bullet that doesn’t have a crimp groove degrades group size by an average of 40 percent. Other than the crimp die, we have no problem with our bullets in that firm’s dies, although our preference is for RCBS® products.
We express ours thanks to the die maker for allowing us to make contact with so many new SPEER customers.