Vet66,
Hornady's load development system is unclear to me. The manual claims a pressure test gun is used to develop the loads, but their velocities are all from commercial rifles instead of taking advantage of the test gun barrel to get a velocity the way ammo manufacturers and powder companies and Lyman do (in most instances). What I suspect is they do what Speer does, and that is develop loads in the commercial firearm, watching for pressure signs and aiming at particular velocity bands, then send ten of the warmest of these for pressure testing to make sure they haven't gone over SAAMI's MAP value. If that comes off too high, they would back a load down, but if it comes off low, well, they had their other signs, so why raise it up if they are happy with the velocity?
But that's just a guess. I have observed they (Hornady) will have maximum loads on the same page that vary from about the same as other sources who are using their bullets, to more than 10% below those other source. Mind you, pressure varies exponentially with powder charge, so 10% less powder is producing somewhere in the range of abut 15-30% lower pressure, depending on the powder characteristics.
In Hornady's defense, I'll also note that the old copper crushers are known to give readings that vary over 20% from one facility to the next, so it's actually possible, on the old equipment, to get that kind of disagreement. The modern Piezo transducers have about half that variability, though. Also, if it were just a matter of different instrumentation, you'd expect the data to be higher as well as lower than everyone else's, but I find it is rarely higher. There was an example of them having a load that was higher than Alliant's recently. Pistol load of 2400, I think. But is was lower than Lyman's number.
Hornady's load development system is unclear to me. The manual claims a pressure test gun is used to develop the loads, but their velocities are all from commercial rifles instead of taking advantage of the test gun barrel to get a velocity the way ammo manufacturers and powder companies and Lyman do (in most instances). What I suspect is they do what Speer does, and that is develop loads in the commercial firearm, watching for pressure signs and aiming at particular velocity bands, then send ten of the warmest of these for pressure testing to make sure they haven't gone over SAAMI's MAP value. If that comes off too high, they would back a load down, but if it comes off low, well, they had their other signs, so why raise it up if they are happy with the velocity?
But that's just a guess. I have observed they (Hornady) will have maximum loads on the same page that vary from about the same as other sources who are using their bullets, to more than 10% below those other source. Mind you, pressure varies exponentially with powder charge, so 10% less powder is producing somewhere in the range of abut 15-30% lower pressure, depending on the powder characteristics.
In Hornady's defense, I'll also note that the old copper crushers are known to give readings that vary over 20% from one facility to the next, so it's actually possible, on the old equipment, to get that kind of disagreement. The modern Piezo transducers have about half that variability, though. Also, if it were just a matter of different instrumentation, you'd expect the data to be higher as well as lower than everyone else's, but I find it is rarely higher. There was an example of them having a load that was higher than Alliant's recently. Pistol load of 2400, I think. But is was lower than Lyman's number.
