Interesting thread. Can you (John or Charlie) tell if you have experienced a pressure change with faster or slower twist rates?
It was an argument in another thread here years ago.
I'm not sure that is a question that strain measurement can answer definitively. Mounting a gage on a barrel makes it a unique system that provides strain measurements. You then have to calculate the pressure given a multitude of factors such as barrel dimension, brass hardness etc etc. Mount a gage on a different barrel and you've created a different system subject to it's own calibration etc. Calibration between barrels (systems) is a challenge unless you're prepared to use a high pressure oil system as Harold Vaughn did or have access to expensive high pressure measurement equipment. I had a reference lot of ammunition that I'd fire before each session to ensure all was as expected. As imperfect as that was, it was as simple and practical as I was willing to go. Ristow felt that his computer algorithm did a good enough job with calibration. I was skeptical.
From a purely engineering perspective, the energy required to increase spin on a bullet (for us it was going from 1/8 or 1/7 to 1/6.5 was neglible. This was borne out in our firing tests. Same load in same chamber design shot to pretty much the same velocity whether it was in an 8, 7 or 6.5 twist.
Mr. Sisk, I'm curious how you're calibrating your PT? Are you going with the software calibration?
