Kind of hate to tell you this, but the early Speer manuals didn't use actual pressure-testing equipment--and that continued for quite a while. I eventually figured this out with a lot of research, including Jack O'Connor's more obscure writings..
They did buy copper-crusher equipment, but apparently nobody working there could figure out how to use it correctly. They got widely varying results--I would guess because they didn't test in consistent temperatures. Have visited the Speer plant in Lewiston more than once. Lewiston regularly gets over 100 degrees during the summer, and sometimes under zero in winter, and the original buildings were NOT well-insulated, much less temperature-controlled.
So instead Speer used traditional pressure "indicatiors," primarily measuring case-head expansion. All of these have been proven to be inaccurate with modern pressure equipment, mostly because brass varies quite a bit in hardness. Which is why a lot of older manual data has been toned down, and not just from Speer.
I somehow missed getting a copy of the 1969 Speer manual, but do have the 1974 (9th) edition. By then they had decided to use actual pressure-test equipment, probably at the urging of SAAMI. The maximum velocity for 175-grain bullets is 2875 fps, from a 24" barrel.
I have been able to beat that by a little bit with newer powders, but not by much.
I realized this^^^
I was referring to a section where they chronographed factory ammo
I got banned on another web site for a debate that happened on this site. That's a first
