THE KING

[colorado]

The 6.5 Creedmoor of DG cartridges

exactly, I love the 375 H&H but hype breeds hate

 

[Mark A Ouellette]

Gentlemen,

This is an example of a pressure curve.
Pressure builds and peaks as the bullet starts to move and then is swaged into the rifling. If you have ever tried to fit a bullet into the proper sized barrel you will very much appreciate that pressure swages a bullet into the rifling! That is where peak pressure is.
If you do not believe this just examine most any centerfire rifle barrel. Notice the thickness of the barrel surrounding the chamber?

A decade or so ago I used a Pressure Trace tool to develop loads. The results were similar to this example.

 

[Ray B]

The above graph shows what I am discussing. the way to increase velocity without increasing the maximum pressure would be for the powder to be signed in such a way that the pressure peak shown at .5 then instead of dropping, the pressure could be maintained at the high level until1.0, then burnout and pressure drop to existing levels at 1.5. As long as the action/barrel has sufficient strength to handle the extended duration of pfressure, I'd expect significantly higher velocities.

 

[PHOENIX PHIL]

I would say that the area underneath the curve is what is most important first. When you think about this for a bit, you’ll realize that peak pressure, provided it’s within a safe operating range, really doesn’t matter.

It’s the application of pressure in such a manner as it creates accelration of the bullet. This means in theory that one powder can have a lower pressure peak, but if the drop off of the pressure is slower, it may be more efficient in the end.

Looking at the graph above, I would tend to guess that the T4 powder and load would give best velocity. Not because it has a roughly 1% higher peak pressure than T2 or T3, or roughly even to T5, but because it maintains the overall pressure longer. This is another way of saying the area underneath the curve of the T4 powder looks to be the largest.

You can kind of compare this to a drag racing car that may come off the line a little slower than it’s competitor but maintains it’s accelelation down track longer and ultimately wins with a resulting overall faster track time.

 

[Bob Nelson 35Whelen]

I would say that the area underneath the curve is what is most important first. When you think about this for a bit, you’ll realize that peak pressure, provided it’s within a safe operating range, really doesn’t matter.

It’s the application of pressure in such a manner as it creates accelration of the bullet. This means in theory that one powder can have a lower pressure peak, but if the drop off of the pressure is slower, it may be more efficient in the end.

Looking at the graph above, I would tend to guess that the T4 powder and load would give best velocity. Not because it has a roughly 1% higher peak pressure than T2 or T3, or roughly even to T5, but because it maintains the overall pressure longer. This is another way of saying the area underneath the curve of the T4 powder looks to be the largest.

You can kind of compare this to a drag racing car that may come off the line a little slower than it’s competitor but maintains it’s accelelation down track longer and ultimately wins with a resulting overall faster track time.

@PHOENIX PHIL
Avery good analogy.. Peak pressure is no good unless it can be maintain a slower drop in pressure. If there's nothing left to burn pressures can't be maintained so speed can actually decrease. Look a a 22lr fired in a 16" barrel compared to a 24". Velocity is higher in the shorter barrel as all the powder has been consumed and pressure is still good. In a 24 inch barrelall the powder is consumed therefore the bullet is relying on what is left to exit the barrel. Extra time in the barrel is extra friction using up this pressure hence lower velocities.
If a powder can burn progressively and maintain the pressure curve in a flatter way instead of falling off sharply velocity has to increase. That's the beauty of some of these newer powders, they maintain the pressure curve for longer.
Bob

 

[mark-hunter]

A decade or so ago I used a Pressure Trace tool to develop loads. The results were similar to this example.

Never heard of this. Very interesting.

Can you give more details how does it work?
Price?
Some photo?

 

[Mark A Ouellette]

Never heard of this. Very interesting.

Can you give more details how does it work?
Price?
Some photo?

I could but you will get more information if you do a simple Google search.
Here it is:

Rifle Barrel Chamber Pressure Testing Hardware & Software | Pressure Trace

Measure ACTUAL rifle chamber pressure for each shot, barrel harmonics, rise time, time to muzzle exit and OBT barrel timing.

www.shootingsoftware.com