Secondary Pressures

[fguffey]

I am reminded of John Godfrey Sax and the story about an elephant 6 men had never seen.

http://www.jainworld.com/literature/story25.htm

Or ‘scardie’ cats afraid of something they can not see or understand. ‘THE SPIKE’ , industry changes the method and or technique for testing pressure and then the change sends shivers through the masses. Nothing changed; I would not walk across the street to watch an ant eat a bail of hay, what I would not want to do would be standing between the ant and a bunch of reloaders.

Again, there are claims the bullet clears the barrel with no consideration given to distance and time. When a reloader tries to explain the event in the scariest terms no consideration is given to the fact the bullet is setting still and starting from a dead stop. No thought is given to the bullet taking off from a dead stop and then being slowed down when it hits the rifling and no consideration is given to the fact the bullet must start turning in the rifling. No one considers what happens when the bullet is setting against the rifling and must start moving from a dead stop while jammed into the rifling. And again; there is that 8mm bullet in a 30/06 chamber or the shooter that was going to sue the ammo manufacturer and Winchester because he purchased 308W ammo for a 25/06 chambered rifle.

And then there are all of those reloaders that could only imagine how long the 308W bullet was when it left the barrel of the 25/06.

F. Guffey

And I have always said if only there was something in the chamber when the trigger was pulled. And then I always say “Wait! There is something in the chamber when the trigger is pulled, it is called a case. The case is in the chamber when the trigger is pulled and I always ask; “Who measures before and again after?”

[fguffey]

Ruggyh, can you read a map? Can you read a scope? The scope I am talking about reads voltage, resistance and time. I know, I lost you at voltage.

You did a cut and paste of a drawing you do not understand. I understand this forum is full of members that are impressed with that type of behavior. This is not the first time I have seen the illustration, the first poster of that cut and paste job you posted has not been civil to me since he posted it. He jumped out into the fast lane and hit the wind, it was not my job to embarrass him, I thought he did it to himself.

If the spike that goes straight up in a very short time is the secondary spike, where is the primer spike? In a step up transformer there are two windings; one is the primary winding and the other winding is called the secondary winding.

Deductive reasoning says if there is a secondary there must be a primary so; where is the primary spike? What causes the primary spike? What causes the secondary spike?

F. Guffey

[LynnJr]

95% of all Benchrest Shooters use ammunition where the bullet starts firmly against the lands.
They shoot the most accurate rifles on the planet.
And then there are others who shoot old worn out military rifles and think they know about accuracy.
And then there was the guy who had never heard of secondary pressure only to post he knew about it all the time.
Can he be trusted I think not.

[JMP]

95% of all Benchrest Shooters use ammunition where the bullet starts firmly against the lands.

I think there may simply be an issue of miscommunication. Guffey's "running start" method seems to be more similar to factory made ammo when they keep it short to make sure it fits in all of the chambers of that cartridge. In that respect, I believe that Guffey may have reduced spikes to a certain degree.

Whereas LynnJr, is looking at it from the perspective of loading accurate ammo notwithstanding concerns of excess pressure. The excess pressure or spikes are also less of an issue since you work your load up from known safe levels.

Personally, I like to load as far out to the lands as I can. I don't worry about d(P)/dt as it seems many other reloaders do. I care only about the maximum pressure is safe and I can find a load that is accurate. Once I find a good range of powder, I adjust the seating depth to tune the load. As LynnJr indicated, the place to start is the lands. Then, you work back only in one direction. That's the easiest way to work up a load. If you do it properly, you should be able to nail a good load after just a trip or two to the range.

I am not opposed to Guffey's "running start" method. I will use the "running start" method if it shoots better than it shoots close to the lands.

The other thing that may be at play here that is causing a misunderstanding is that LynnJr, I believe, has tight chambers with a short throat that is cut to his preferred specification. If you are talking about old rifles, then yes, the chambers are large and the freebore is so long that you can't even seat a bullet out to the lands. Then, you are forced to use the "running start" method.

[LynnJr]

JMP
When you start a bullet way short of the lands it takes very little pressure for it to get started but as soon as it hits the lands it slows down until the pressure builds.
We are not talking about much pressure here.
Guffey jumps his bullets a long way because he is only concerned with his gun going bang and not accuracy.
The chamberings he uses are old military rounds were 2 moa is a good grouping.
It is extremely hard to make a 6 PPC shoot 3/4 moa as they are inherently accurate.
If we look at the timeline the secondary pressure spike has nothing at all to do with seating or grab but Frank can't read the graph or doesn't understand it or both.
The graph represents the bullet nearest the muzzle not the chamber and the use of slow burning powders.
The spike in theory is caused by the heavy for caliber bullets getting accelerated and out running the pressure against the heel of the bullet. A secondary explosion or detonation takes place and we see the spike.
As Guffey can't read the graph he still thinks it is seating depth related and comes up with these wild ideas of his which spread misunderstanding and confusion. He then posts some nonsense not vaguely related to the subject at hand in order to show us he has read some funny internet stories.