Soooooo many unproven theories on reloading. People will read something, then tell the world it is the gospel truth, without bothering to actually know if it is the truth they are preaching.
A case that comes to mind.
We "know" it is extremely dangerous to use mixed brands of cases when reloading, because this is what is stated on the gun nutz. Got to scratch my head on this one, because I think it is safe to say that those of us who have been reloading for half a century, once paid little attention to brands of cases we used. And guess what? The sky didn't fall and our rifles stayed in one piece.
We did discover that cases that weighed on the order of 30 grains heavier, like some military cases, had to be loaded down a grain or two of powder.
But as far as I was concerned, if the cases weighed within ten grains of each other, I considered them equal.
Eventually, I got around to testing this out, using my Marlin bolt action 243.
I had Federal, primed 243 cases that weighed 179 grains and primed Winchester 243 cases that weighed 169 grains. I loaded 46 grains of H414 powder in both types of cases, behind a 75 grain Sierra HP bullet. Here are the results of firing each group over a chronograph.
46 grains of H414, 75 grain Sierra HP bullet, Winchester cases weighing 169 grains average----------3491 fps.
46 grains of H414, 75 grain Sierra HP bullet, Federal cases weighing 179 grains average--------------3468 fps.
Damn, what happened to that theory that states that heavier cases will create more, maybe dangerous pressure, and thus give more velocity?