"But as long as the pressure does not exceed 11,500 psi for a 12 bore, they're good to go. But if they say the velocity is 1330 fps, for example, that's going to be pretty close."
Larry with the different loads out there now, you can no longer state what you wrote above. As you can see from this recipe from the Alliant site, this is pretty close to your 1330 fps and nowhere close to SAMMI.
This load is for 3/4 oz. shot using 12 gauge Remington Gun Club or Nitro hull.
16.0 Extra-Lite Rem. 209P CB0175-12 1310 7300
I use a load similar to this using Titewad instead, the fps is a little slower.
JDW, you're misinterpreting what I said. I'm referring to FACTORY shells, not reloads. But my point is this: Just because you test a particular factory load and find that it produces a pressure of, say, 9,500 psi, you cannot be confident that the exact same load--same company, same shot charge, same velocity (or dram equivalent) marked on the box--will produce the same pressure if it comes from a different lot. Ammunition makers vary the powders that they use. They don't worry about pressure, other than to make sure that they stay under the 11,500 psi SAAMI service pressure ceiling. The next shell you have pressure tested may develop 8,000 psi or it may develop 11,000 psi if those shells are from different lots. But they will all be quite close to one another in velocity, because velocity is the constant towards which the ammo companies work.
Even though my point was in reference to factory loads, it's easy enough to confirm by looking at reloading books. You can have higher pressure loads that produce lower velocity than lower pressure loads. And you can have a higher pressure load and a lower pressure load that produce the same velocity. If we shoot vintage guns, we worry about pressure. Winchester, Federal, and Remington do NOT worry about pressure other than not exceeding the SAAMI maximum because their loads are not designed for our guns. Their major concern is sticking to whatever velocity is marked on the box. RST, on the other hand--making shells designed for our vintage guns--will focus on pressure. For obvious reasons.
