Quickload's OBT feature

[Bart B.]

I like twice fired and you don’t size them the chamber has done it for you

Are they perfectly round?

 

[savagedasher]

Are they perfectly round?

Depends on the chamber they came
from

 

[Bart B.]

Long's OBT theory is based on his belief the muzzle diameter pulses larger by several millionths inch several times during the bullet's transit time through the barrel. If the btullet exits at the larger diameter, accuracy somehow is less. How that changes bullet direction isn't mentioned.

When I put a front sight holding clamp on the muzzle very tight, that squeezes the bore diameter down a couple ten thousandths inch. Accuracy doesn't change for a given load without the tightened clamp on the muzzle. Bore diameter changes verified by hole micrometer and bore erosion gauge.

Long's barrel resonant frequency numbers are several times higher than they really are.

Long says the mass of the barrel precludes the round's firing shock excitation from getting to the muzzle in any significant amount. It will start to “ring” but won’t get really shaking until the bullet has left. This filtering makes the muzzle position very insensitive to the charge and seating depth. If his were true, then tuning the muzzle vibrations with a weight's position at the muzzle would not be possible. Tuning weights really work well so slower bullets leave it a higher line of fire angle than faster ones.

 

[Bart B.]

Depends on the chamber they came
from

And their wall thickness uniformity. Worst ones have their pressure ring highest at the thinnest part. Uniform pressure ring height is a good indication of uniform case wall thickness.

 

[BCBRAD]

Primers and different lots of the powder can add another unknown

QL is not derived from a test barrel or any other 'hardware', it is physics projected with mathematics to produce a model.

Any differences will be seen in velocity, velocity is the grail, all variables will produce a velocity.

With out accurate velocities the program does not work as well as it should/could.

Primers do influence velocity but are not accounted in the program. A hot primer that increases pressure, therefore , velocity will require a bit less powder and so on.

QL basically, with quality inputs, is about powder charge.

 

[savagedasher]

QL is not derived from a test barrel or any other 'hardware', it is physics projected with mathematics to produce a model.

Any differences will be seen in velocity, velocity is the grail, all variables will produce a velocity.

With out accurate velocities the program does not work as well as it should/could.

Primers do influence velocity but are not accounted in the program. A hot primer that increases pressure, therefore , velocity will require a bit less powder and so on.

QL basically, with quality inputs, is about powder charge.

But it is better then any reloading book

 

[CharlieNC]

Over the years my informal assessment is the overwhelming majority of those who use Quick Load in conjunction with Optimum Barrel Time report the system works quite well to provide an accurate starting from which the node can be fine tuned using fewer charges. As previously mentioned this considers many powders, bullets, etc from which the basis can be chosen. Only occasionally does someone report the approach fails, but it is certainly not 100% accurate.

I am in that category, and don't fret because C Long's theory does not fit what I may or may not believe is the fundamental mechanism of the harmonic behavior. It has worked to well for me to dismiss its application. But this deters many from trying the approach, simply stating it is wrong and cannot work.