When Jack O'Connor started using H4831 in the .270 it was all about "chasing velocity," even though handloaders had to take his word (and that of the loading manuals) back then. The truth was that the original mil-surp powder Bruce Hodgdon eventually called H4831 didn't get much more velocity out of the .270 than IMR4350, which had already been around for close to a decade.
The other side of it is that before cheap chronographs appeared, many people thought they were chasing velocity but were mistaken. I bought my first .243 Winchester in 1974, and since it was the exact same model Speer used in their manual, and I used exactly the same load, I assumed the muzzle velocity of my handloads was right around 3000 fps. Bought my first chronograph five years later and found my handloads weren't quite getting 2800 fps.
A friend (another gun writer) had the same experience with his 7mm Remington Magnum. After buying a chronograph he found he'd been using what was essentially a warmly-loaded 7x57 for many years. Since he lived in a heavily timbered part of Montana, where big game was almost never shot over 200 yards, it didn't make any difference to the deer, black bears and elk his "magnum" killed.
Actually, I'm surprised some people don't claim they still use Cordite, since it worked fine in the 1890's.
“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.” John Steinbeck
