how do you reconcile differences like that?....... I'd be curious as to thoughts of the more experienced. Thanks.
Maybe I've been at this too long...(been reloading for about 45 years) but it continues to amaze me how many people don't realize that loading data is not handed down on stone tablets from on high, nor is it the immutable laws of the universe, but like the pirate says "more loike guidelines, really...aarrr"
Simply put each gun, and ammo component is a variable. They DIFFER slightly. THEY ARE NOT ALL EXACTLY THE SAME. Even if your gun is the same make model and barrel length as their test gun, its not their test gun, and you CAN get different results.
Often, the differences are not noticed without special investigation, but sometimes the differences are drastic. That's why we always start low, and CAUTIOUSLY work loads up.
A load that works fine in gun A might show high pressure signs in another gun. They are all different even consecutive serial number guns off the production line could show large differences in what they shoot best, worst, and what is, and isn't high pressure in them.
Most of the time, guns and ammo will behave about the same way, but sometimes things are much different (stacking tolerances is one explanation), and there's no way to tell beforehand, which is why one always starts low and works up, starting over whenever you change ANY component.
Here's an example I was involved in, three different guns, all .357 Mag, all shooting the same ammo, over a chronograph. A 6" S&W M19, a 6" S&W M28 and a Desert Eagle.
125gr JHP, load right out of the middle of the Speer manual, but worked up in a different gun.
The M19 shooter doubled the gun on his first shot (I had never heard of anyone ever doing that with a .357, but he did it) At that point we discontinued shooting the model 19, and the two fired cases had to be driven out of the cylinder with a rod and a hammer. We could not get them out by hand. (and I did the rest of the shooting
)
Chrony said 1620fps
Full cylinder from the model 28. Cases ejected normally.
Chrony said: 1670fps
Full magazine from the Desert Eagle. Completely normal function.
Chrony said: 1720fps
Same load, different results in different guns. USUALLY the difference is not nearly that extreme, but extreme differences can, and do happen.
The simple answer is that everybody's data differs slightly because they are using different guns, different lot# of powder, different lots of cases, different bullets, seating depths, crimp etc.
They accurately report what THEY got, but what you or I get, even with as close to the same components as we can match, can be different.