Varminterror
Member
- Joined
- Jul 17, 2016
- Messages
- 14,995
Don’t overthink this. We’re driving on a super-highway, not riding on a razor edge. MAP’s are established with a generous safety margin, and it’s really not pertinent to assume every equal integral of a pressure curve represents the exact same curve, nor that the same velocity (within our margin for error in measuring velocity) is an indicator of the exact same integral of the pressure curve. Ain’t non-linear math fun?
Here’s an example: two barrels from the same manufacturer with the same specs, reamed the exact same day on the exact same reamer, yielding two chambers within 5/10,000 in headspace and bolt-face-to-leade length. Both of these matching two other barrels from the same manufacturer a year prior, chambered to within the same standard by the same smith on the same frame. Using the same lot of bullets, same lot of powder, primers, and brass, and the same load - three of these barrels gave velocity within a handful of fps... all 4 produced signs of excessive pressure at the same charge weight and all 4 produced a velocity node within 1/10th of a grain.
But one barrel produced velocity ~80fps faster than the other 3...
Here’s an example: two barrels from the same manufacturer with the same specs, reamed the exact same day on the exact same reamer, yielding two chambers within 5/10,000 in headspace and bolt-face-to-leade length. Both of these matching two other barrels from the same manufacturer a year prior, chambered to within the same standard by the same smith on the same frame. Using the same lot of bullets, same lot of powder, primers, and brass, and the same load - three of these barrels gave velocity within a handful of fps... all 4 produced signs of excessive pressure at the same charge weight and all 4 produced a velocity node within 1/10th of a grain.
But one barrel produced velocity ~80fps faster than the other 3...