Let's say the premises that barrel movement before the bullet leaves the barrel is to small to effect the accuracy.
Is there data that measures at least two points - looking for null/node and barrel muzzle- what are those measurements?
Why is this so important- because I an send a piece of metal into vibration in which it is moving in opposite directions at each end and the center can be moving in directions separate of the exterior. To say these forces don't occur in a barrel needs data.
This data does exist, using both eddy current sensors and laser vibrometers. It shows small amounts of movement, and variation in that movement does affect dispersion. I suspect a clever arrangement of sufficiently sensitive strain gages could also work, but would leave out the rigid body motion that occurs.
The premises being proposed is that the energy produced continues to gain after the bullet leaves the barrel. The premises is that energy is still being released and gain is still occurring after the bullet leaves (what is the energy source). I find that removing an energy source almost immediately stops the vibration. Are there other examples of systems gaining amplitude after the source is removed? In my simple mind that is gaining perpetual motion - new term. LOL
That's not the premise being proposed, but even if it was, the powder column is still acting on the barrel. The removal of the projectile does not imply the removal of all forces. Beyond that, the fact that the barrel movement is larger after bullet exit than before is easily observable. As you yourself have pointed out, current high speed cameras are not capable of resolving the lateral movement during barrel time, yet there are many videos showing movement after bullet exit. The obvious conclusion is that the barrel is now moving enough to be within the resolution of the camera.
Lets say the premises that the bullet and the case (all components within) are the primary driver of accuracy (removing recoil management). To at least some on here - the only driver.
With that if the precision loaded round is the only contributor:
1) How does the precision round know the shot string count and then degrade.
2) Does the degrading group open up or only drop in vertical.
3) If it is expansion of the barrel/bore- then we should be able to create a load that compensates for this change and reduce the group size (question)?
4) If I scribe a line on a bullet will the group degrade?
5) If I dent a bullet will the group degrade?
6) If I precisely load a round as humanely possible- will it shoot the exact same cold bore shot time after time? By some premises -yes.
7) Why does anything beyond a pencil barrel exist?
8) I believe bull barrels are used to keep consistency as heat builds. As heat build barrels distort. However, distortion, is not a "jumpy" random event. Groups get bigger in all directions. How does the round know this and respond to this? Assuming heat is, within reason linear, than I would think the continuing rounds would just make a "line" as the barrel is shot, not random opening group size.
9) With the premises that the round is the only system component that creates accuracy (removing the shooter)- should we/I understand that any given bullet loaded precisely and compensated for twist rate- all will shoot the same group size, same group location(Left right) given a sufficient sample size (For Drew- honest question). Even our barrels will throw some left right into a group with enough speed variation (2200fps to 3400fps same bullet, powder and case).
10) If we assume a barrel will shoot a longer string of accurate shots on a cold day- how does the round know this? If it was the round only, quite simply, why does it just not shoot 100's of rounds accurately if the barrel has no impact from a vibration point.
I think you're strawmanning here (no one thinks that the barrel has no effect), but some of those questions are interesting regardless.
1) Troll question - barrels obviously change with shot count
2) Depends on the type of degradation. If you agree with Litz that the first sign of a barrel going out is BC variability then you will see vertical spread increase first. Opening of the entire cone of dispersion will come later.
3) Probably not, small changes in powder charge are unlikely to cause a large change in obturation.
4) Depends on the line, but yes. Any change in projectile mass balance will have negative effects. Scribed lines with radial symmetry won't have this effect.
5) See 4)
6) Yes, provided nothing in the gun has changed either.
7) More mass more better (unless you have to carry it for long distances, also notice I didn't say stiffness)
8) If you aren't just being snarky, there's a pretty clear explanation as to why the group is opening in all directions. Two of the largest contributors to dispersion are lateral throwoff and aero jump. Both are influenced by asymmetric engraving and in-bore yaw. As a bore expands, the amount of yaw possible increases, but the direction in which it occurs is random. This results in a increase in the entire cone.
9) Not worded clearly enough to answer. Same strawman about barrel not having any influence.
10) See 8)
Concerning the bore and rifling (musing thoughts) - why don't some barrels just plain not shoot? Bad rifling or bad material. Please - a barrel person should answer this. This should be a measurable predictable event. Why does the term "hummer barrel" exists- opposite of a bad barrel?
It should be measurable and predictable, but it's not. A person could make a killing in the custom barrel market if you could tell a good from a bad barrel simply by inspection. This excludes things like comparing a barrel at SAAMI max bore and groove vs one at min, the outcome there is at least somewhat predictable.
If harmonics have no effect on a shot- will a non-heat treated barrel - for a a limited set of rounds- shoot as good as a group as a heat treated barrel?
Yes, but that's nothing to do with harmonics.