Reloading assumptions

Aguila Blanca said:
I must respectfully disagree with the bolded potion of the above statement.

I am primarily a handgun shooter, and ALL my reloading to date has been for handgun rounds. If you've ever seen the great balls of fire that come out of the muzzles of some handguns with some rounds, you would know beyond any doubt that the propellant combustion did not end when the bullet started moving down the barrel.

In fact, several years ago I started an experiment to quantify the loss of muzzle velocity shooting the same ammunition out of shorter barrels. I'm a 1911 guy at heart, so I gathered up a collection of Para-Ordnance pistols (I chose the same brand in the hope that barrel manufacturing would be similar enough to minimize the variable that I was NOT doing what Ballistics By The Inch does, and using a single test barrel that gets lopped off an inch at a time as they run each series of tests) with barrel lengths of 5", 4-1/4", 3-1/2", and 3".

I started out with the near screen of the chronograph ten feet from the muzzle. All went swimmingly for the 5" and 4-1/4" pistols, but the experiment unraveled when I started shooting the 3-1/2" P12.45. Out of ten shots, probably half registered "Error" rather than a velocity. It got even worse with the 3" P10.45.

I was testing five rounds each of several different commercial loads through each pistol, and it was the same ammo that caused the problem in most of the cases. It became clear pretty quickly that with the shorter barrels I was ejecting enough still-burning powder that the glowing particles were messing up the screens. (I was at an indoor range, using the powered infrared sky screens.)

Moving the chrony out to a distance of fifteen feet resolved the problem but, by the time I had that all figured out, I had used up the amount of time the range owner was willing to have that portion of the range shut down. I have always intended to run the experiment again, using two pistols in each barrel length rather than one, a fifteen foot chrony distance, and more rounds of fewer ammo types in order to get a better sampling. I just hanven't had the time to do it.

The point of all this is that if there's burning powder passing through the chronograph ten feet in front of the muzzle, the propellant clearly hadn't all stopped burning as soon as the bullet started to move. In fact, one of the keys to the so-called "short barrel" self-defense rounds most of the major ammo makers started offering about ten years ago is faster powders, with the goal being to have the pressure peak sooner rather than still be increasing when the bullet exits the muzzle.
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I would have to agree with you. No way peak pressure is reached when all the powder burns. All the powder does not burn until after the bullet exits the barrel. That is why we have muzzle flash.
 
Well, a lot of muzzle flash is also caused by unburned hydrogen coming out hot and igniting when it meets oxygen in the air. The role of flash hiders is to create a space that slows and cools expanding gases before they make full contact with the air, thus reducing combustion temperature and completeness.

Cellulose hexanitrate, the main form of nitrocellulose in smokeless powder, has what is called a negative oxygen balance of just over -24%, meaning there is a -24% shortage of enough oxygen in the molecule to combust all the hydrogen, carbon, and nitrogen it releases. So you still have some of those fuel molecules looking for a chance to find oxygen to burn them as they exit the muzzle. Hydrogen has the lowest ignition point, so if it is still hot enough, it is what burns first. Carbon has a higher ignition point in air and has a tendency to condense out on the cooler bore, which is part of why you get unburned carbon left over in the bore. 100% combustion wouldn't leave any carbon.

Nitroglycerin, on the other hand, has a positive oxygen balance of about 3½%, so it actually gives the nitrocellulose in a double-base powder a little oxygen help, but not enough to eliminate the majority of the unburned fuel gasses. Nonetheless, it provides a small but real increase in the energy that is extracted from the nitrocellulose, as well as providing its own energy, which is why double-base powders are often called "high energy" powders.

The bottom line is that you can get some flash whether the powder has burned out or not, particularly if the barrel is short. This was demonstrated to us during night firing at the Gunsite 270 basic rifle class. The difference in the flash from an 18" 308 bolt rifle barrel and from a 22" bolt rifle barrel using the same ammo and neither having a flash suppressor was dramatic. A big white fireball versus a much less voluminous yellow-orange flash. That difference is due to cooling as well as less burning powder remaining after going through the longer barrel.

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Unclenick said:
Well, a lot of muzzle flash is also caused by unburned hydrogen coming out hot and igniting when it meets oxygen in the air. The role of flash hiders is to create a space that slows and cools expanding gases before they make full contact with the air, thus reducing combustion temperature and completeness.

Cellulose hexanitrate, the main form of nitrocellulose in smokeless powder, has what is called a negative oxygen balance of just over -24%, meaning there is a -24% shortage of enough oxygen in the molecule to combust all the hydrogen, carbon, and nitrogen it releases. So you still have some of those fuel molecules looking for a chance to find oxygen to burn them as they exit the muzzle. Hydrogen has the lowest ignition point, so if it is still hot enough, it is what burns first. Carbon has a higher ignition point in air and has a tendency to condense out on the cooler bore, which is part of why you get unburned carbon left over in the bore. 100% combustion wouldn't leave any carbon.

Nitroglycerin, on the other hand, has a positive oxygen balance of about 3½%, so it actually gives the nitrocellulose in a double-base powder a little oxygen help, but not enough to eliminate the majority of the unburned fuel gasses. Nonetheless, it provides a small but real increase in the energy that is extracted from the nitrocellulose, as well as providing its own energy, which is why double-base powders are often called "high energy" powders.

The bottom line is that you can get some flash whether the powder has burned out or not, particularly if the barrel is short. This was demonstrated to us during night firing at the Gunsite 270 basic rifle class. The difference in the flash from an 18" 308 bolt rifle barrel and from a 22" bolt rifle barrel using the same ammo and neither having a flash suppressor was dramatic. A big white fireball versus a much less voluminous yellow-orange flash. That difference is due to cooling as well as less burning powder remaining after going through the longer barrel.

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So, when any component of powder does not burn in the barrel, the powder did not burn completely in the barrel.
 
So, when any component of powder does not burn in the
barrel, the powder did not burn completely in the barrel.
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No, Rather what was said is that muzzle flash is no less combusting gases, as unburned powder itself.

That actual powder is also left unburned is self-evident from the particulate residue on the bench/floor.
 
I don't believe muzzle flash is caused by unburnt powder, but I have seen sparks fly from the muzzle along with the muzzle flash which I attribute to partially burnt or unburnt powder being ignited by the muzzle flash that Unclenick described.
 
Unburnt Powder, and hot gases making a fireball with fresh O2 outside the muzzle, are two very different things. If you want to see unburned powder try a compressed load of WC872 in anything. It will leave a trail down the barrel.
Hot gasses, generated by complete powder burn, will still produce muzzle flash as residual combustibles gasses hit fresh air. That does not mean the powder charge is still burning.
All the O2 required for combustion of powder come in the powders themselves. Otherwise you would need fresh air for firing, which you obviously do not.
 
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