I was at the range last week, zeroing my .308 before a stalking trip. An older member turned up, with some new factory ammunition and some reloads using the supposed same powder as in the factory stuff. He had obviously pulled a factory round to get the weight of powder in them. He wanted to put both loads over his Chronograph to check the MV. Ho asked another member to fire them, as he couldn't get down on the floor. The first two, factory, went through at about 2,900fps. The third, a reload, was fired, with a hell of a bang, gas coming out of the magazine well and the shooter complaining about the recoil. The bolt had to be opened using a lump of 2x2, the primer pocket had expanded with the primer out. The headstamp was almost missing from the case but was imprinted on the bolt face. Either the powder manufacturers use is not the same as we can buy or he made a catastrophic mistake in weighing the powder. Incidentally the bullet was doing 3,700fps.