The barrel velocity in the vibration cycle changes in the horizontal and vertical dimension so that there are periods where the barrel is moving slowly as opposed to periods when it is moving fast. This is the theory behind harmonics and vibrations such as node 1. In Chris Longs theory it's about the wave being away from the muzzle. In both cases these concepts create wide nodes. I would recommend you read :
I’ve read it and I get the theory, but I’m not sure it is practical. Do the harmonics work tomorrow the same as today?
1. Doesn’t barrel time change from lot to lot of powders?
2. How are you supposed to depend on Quick Load or GRT to predict the barrel time in your rifle? I’ve heard of people that had two identical barrels, made with the same reamer and same gunsmith, on the same action and they liked completely different loads.
3. What about ambient temp? Your barrel time is gonna change constantly.
4. Has anyone tested OBT in decent sample sizes against control loads? Across different weather conditions, altitude, elevation etc.
I just have a hard time believing OBT is practical or predictable when there are so many variables like powder lots, temperature, barrel variations, chamber variations, primers, bullets, brass, neck tension, elevation. Suppressors, etc. I think if OBT is to be used as a practical solution it would need to be in a very controlled environment with as few variables as possible. Short range Benchrest maybe or in a tunnel range.
