This relates to a discussion on the Cast Bullet forum on hangfires.

I am under the impression that the design of the powder is such that on ignition all of the powder granules are burning at the same time and the "progressive" nature of the burn is due to each powder granule's makeup.

On the other hand, when the sprk plug fires in the car engine the flame gradually spreads throughout the whole fuel/air mix as if it was a single grain of powder.

Anyone know or have some ideas.

Mike

Mike,

Powders burn gradually - from primer to bullet end.

I don't have any scientific data to support this, but this is what I believe happens.

In our time frame of reference they may seem to burn all at once, but they do burn from one end to other.Takes only
milli-seconds, IE when powder near primer is all burnt the last near front may be only half burnt and the bullet is on its way.In 1.5 to 3 inches of bullet travel it has reached peak pressure(depending on powder speed), most of the powder that will burn is in gase form, and the chemical reaction that makes up the burning process completes most of its course in the gase form.It doesn't burn 100% to
clean gase products, there are some residues left.Ed.

My theory is:



the primer spark ignites part of the powder which turns into gas excerting a rapid increase in pressure. Pressure increase yields heat increase, and this heat ignites the rest of the powder NEARLY instantly.

This explains why stick powders start burning within their tiny holes simultaniously - a flame could hardly achieve this.



As the combustion process is a "slow detonation" (deflagration), it only partly takes place with the bullet in its place: the bullet starts moving, and the volume of the combustion chamber extends to about 2" within the barrel. Now NEARLY all powder is burnt and pressure lowers. See pressure curves, in QuickLoad for example.



I include NEARLY because some powders and loads do not produce a complete combustion (we all have noticed powder kernels on the floor in front of the shooter) due to chamber volume increase and pressure drop.

Mike,
this is going to sound smart assed, but it's not.

All the granules burning at one time (on an objective scale) would be an EXPLOSION. Modern Smokeless powders do not explode, they BURN, in feet (or meters) per second.

the "faster" powders have a FASTER or MORE feet per second, the slower powders have a LOWER or LESS feet per second.

Or the difference between greendot and H1000

jeffe

Jeffe,

I don't think all the granules burning at the same time will be an exlosion because each granule does not "detonate" but is gradually consumed and the makeup of each granule controls the burning rate.

Mike

If one fires a suitably primed case in their rifle/pistol and holds some susceptable material over the muzzle while doing this one will see how far the primer flash reaches and how much force is obtained. Then imagine this in a loaded case. Supersonic washing machine?

Mike, you should try to get a hold of the current issue of Varmint Hunter Magazine, which has a quite detailed discussion on it.

In summary, it states this: There are three to four things that can happen to powder in a charge:

1) Super ignition. This happens to the granules directly in front of the flash hole. The blast of the primer shatters and instantly ignites these granules.

2) Primary Ignition. Up to about 3/4 inch in front of the flash hole, the primer ignites all the powder through direct heat.

3) Secondary ignition. Powder farther away than 3/4", but not "too far", ignites as soon as the powder lighted in the primary ignition reaches tempererature. At this point, the increased pressure "smashes" the remaining powder into a near solid mass, inhibiting ignition.

4) non-ignition. Powder that is directly under the bullet can be prevented from ignition (heat) by the "plug" of powder that did not directly ignite. It can be pushed into the barrel after the bullet. At this point, because of the pressure gradient in the barrel (lower in the barrel than in the chamber) this powder never ignites. As a matter of fact, if powder hasn't ignited in the first 3 to 6" of barrel, it likely never will.

In handgun charges, the primer flash reaches often to the bullet, so there is no secondary ignition. Most hangfires relate to movement of the bullet due to the primer blast. This greatly enlarges the chamber, and instantly lowers the pressure inside that chamber. Thus secondary ignition is greatly delayed. Solution is a heavier crimp or weaker or stronger primer. FWIW, Dutch.

Jeffe,

Detonation would be dynamite or the primer compound.

Mike

No Mike they don't. You can test this yourself in (2) ways. If you fill a handgun case 1/2 full of any powder & ignite it, you'll see the powder starts to burn & then increases intesity as it hits the middle of the case. Reverse that image & you have what happens when a primer is touched off. The other way to tell is fire something like 20gr 2400 from a 2 1/2" 44mag @ a target 5-6ft away. Do the same w/ a 8" bbl rev. You'll see alot of unburned powder gran. hitting the paper from the 2 1/2" bbl. That's the unburned powder from the front of the case.

Fred,

No doubt you are right.

But I wss thinking more about the "design" as opposed to what might happen as per your illustration.

In other words it is my belief if we fire 60 grains of 4831 with 130 grain 270 and all the granules ignite at once then we will not have an overload.

Mike

And the winner is Dutch!!!!!! roger