Burning Powder

[ab_bentley]

What's the difference between burning 22gr of powder in one case and burning 22gr of powder in a similar case? Specifically the difference between the 20VT and the 20-222.


The reason I ask is people seem to believe that one will burn the throat faster than the other. Is there any evidence to support this theory with other cases?

 

[4Mesh]

What's the difference between burning 22gr of powder in one case and burning 22gr of powder in a similar case? Specifically the difference between the 20VT and the 20-222.


The reason I ask is people seem to believe that one will burn the throat faster than the other. Is there any evidence to support this theory with other cases?

The case with more volume (larger case) will produce less pressure and in turn burn the powder less cleanly. It will be less efficient, and the additional dirt left behind will wear the barrel faster.

 

[ab_bentley]

The case with more volume (larger case) will produce less pressure and in turn burn the powder less cleanly. It will be less efficient, and the additional dirt left behind will wear the barrel faster.

Never thought of that. Point taken. Adam

 

[HovisKM]

I have to disagree to some extent with that explanation, some powders will exhibit this but not all. Some are actually the opposite, in that a higher load density will not burn completely, especially in colder weather. If the cases have very similar capacities, they will show the same burn characteristics, at least close enough to not be able to tell the “dirtiness difference” with the same powder.

Also, I have never noticed a dirtier (fouling) barrel wearing faster. I put fouling afterwards because that is what we are talking about, firing residue. A lot of loose residue is pushed out of the bore ahead of the bullet by the air being blown out of the bore.

Most of the wear of a barrel comes from the heat from firing that follows the bullet. The old rule of thumb was that a longer neck on a cartridge didn’t wear the throat or barrel as fast as a shorter neck. I even remember my dad speaking of this when I was young. However, I really don’t think that is necessarily true. It seems all the cartridges he was talking about burning out throats faster because of the shorter neck were made from a parent cartridge but the shoulder were blown out and a little steeper that made the neck shorter, well, they also had more powder capacity, which in turn creates more heat, which wears a throat/barrel faster.

Just my opinion
Hovis

 

[cdupuy]

What's the difference between burning 22gr of powder in one case and burning 22gr of powder in a similar case? Specifically the difference between the 20VT and the 20-222.


The reason I ask is people seem to believe that one will burn the throat faster than the other. Is there any evidence to support this theory with other cases?

Ab: there is an old belief that the longer Neck of the 222 case will reduce the erosion from powder at the throate.

 

[mike in co]

as hovis pointed out its kinda complicated....

22 gr of WHAT POWDER ?

powders typically have a pressure band where they want to burn and burn efficiently there.

lower than that typically you see unburnt powder.

high velocity and high temp tend to burn throats......all relative to the bore dia.

mike in co

 

[4Mesh]

Look guys, barrels get hot because of friction, not because of fire. A typical bullet leaves a barrel of a centerfire in roughly .002 seconds. In other words, at the 1000 round point, your barrel has been exposed to a GRAND TOTAL of 2 seconds burn time. Not quite enough to do the erosion you guys talk about.

Now, if you think there's heat still in there after firing, fire a round and quickly put your finger over the end of the barrel. Now if the air in there is 2000 deg F, trust me, you'll get burnt. But, you won't, yer safe. So, where does all this "heat" come from? I mean, even if we double that time to 4 total seconds, I think its still safe to say flame does not erode a barrel. Dirt and mechanical wear do. Where does the dirt come from? From the unburnt powder. Your car uses a catalytic converter to convert unburnt emissions into something "less dirty". Less black s--- out the pipe.

The whole heat thing is a perpetuated myth, and there's plenty of people who just ain't willing to let it go.

Here's an experiment. Take a short piece of barrel, scratch it with a carbide scribe so you can see the scratch. now, buy a tank of Mapp gass. Set up your torch and point it at that barrel piece until the tank runs out. Now tell me how much of that scratch is no longer there. Not very much eh?

 

[mike in co]

if you would like to provide some proof( not likely considering the source) of these claims, we might listen.

the pressure AND temp of the burn well exceed your inapropriate mapp gass experiment.(sorta like take a box of 22rim fire long rifle, shoot them till gone and see how much bbl wear you have)

do copper jacketed bullets cause heat and wear, yes, it if the major source of bbl throat wear...no way....

go do the math how much energy is required to force a soft copper jacketed bullet to compress aprox .003 over half its dia in the same .002 seconds...against a ss bbl with a tapered throat, and then again on a chrom moly steel bbl.

question why do 30 br bbls last over 8000 rounds and a 234/6ppc last 2000?? ......here is a clue....less nozzle.......the smaller 6ppc neck creates a nozzle for the gasses to escape thru, thus higher velocity of gas. add the temp of the burn and one has throat errosion.

why do throats look like dried fried desert and not sanded......casue they are high tempature burnt ...not sanded from copper friction.

mike in co

 

[mwezell]

One more point on that subject....How long does it take to pit the boltface of a rifle with leaky or blown primers...or flame cutting of a revolver frame.? Fact is... a smooth surface is burned less than a rough one. The flame does burn away the small burrs and rough edges, so why would it not, eventually toast a barrel?--Mike
If friction were the biggest culprit, barrel wear would be pretty consistent from the point where the bullet is fully engraved to muzzle.

 

[MarkR]

If this were true, then why would there be a difference in barrel wear between a 220 Swift versus a 223 at lets say...1500 rounds?

Look guys, barrels get hot because of friction, not because of fire. A typical bullet leaves a barrel of a centerfire in roughly .002 seconds. In other words, at the 1000 round point, your barrel has been exposed to a GRAND TOTAL of 2 seconds burn time. Not quite enough to do the erosion you guys talk about.

Now, if you think there's heat still in there after firing, fire a round and quickly put your finger over the end of the barrel. Now if the air in there is 2000 deg F, trust me, you'll get burnt. But, you won't, yer safe. So, where does all this "heat" come from? I mean, even if we double that time to 4 total seconds, I think its still safe to say flame does not erode a barrel. Dirt and mechanical wear do. Where does the dirt come from? From the unburnt powder. Your car uses a catalytic converter to convert unburnt emissions into something "less dirty". Less black s--- out the pipe.

The whole heat thing is a perpetuated myth, and there's plenty of people who just ain't willing to let it go.

Here's an experiment. Take a short piece of barrel, scratch it with a carbide scribe so you can see the scratch. now, buy a tank of Mapp gass. Set up your torch and point it at that barrel piece until the tank runs out. Now tell me how much of that scratch is no longer there. Not very much eh?

 

[4Mesh]

If friction were the biggest culprit, barrel wear would be pretty consistent from the point where the bullet is fully engraved to muzzle.

So you are saying that the engraving process at the throat is no more wear than farther down where the bullet is not being formed?

If this were true, then why would there be a difference in barrel wear between a 220 Swift versus a 223 at lets say...1500 rounds?

I already told you that in post #2

the pressure AND temp of the burn well exceed your inapropriate mapp gass experiment.(sorta like take a box of 22rim fire long rifle, shoot them till gone and see how much bbl wear you have)

Ah ha. So, Mapp gas burns at 5300F. You contend that the gas in the barrel "well exceed" that temp. Yet, after the bullet is gone, all that hot air ain't there anymore. It's not hot. Now, how is that possible? Remember, if you want to say its really hot in there, you can't turn around and say it's also cold. It's got to be one or the other, so which is it? Now, me, I happen to know what 1500-2000F is cause I use an oven at those temps all the time. Now, let me tell ya. Something that's really at 2000F, is pretty hot. I bet you can't hold your ungloved hand 6" from the front door of the oven for 3 seconds, and that's cold by comparison to what you claim is in that barrel. Mapp at 5300 is hotter... Sooooo, how much hotter are you talking about? And, remember, you're saying it's cool within 1 sec cause that's how long it should take for you to stick your finger over the muzzle and see if you get burnt. 1 Sec ain't very long for a 5000+ Degree gas to cool to 100F or less. Methinks it ain't that hot.

One more point on that subject....How long does it take to pit the boltface of a rifle with leaky or blown primers

Well, it's also sandblasting that face with the dirt that is being shot out of that case. Especially the glass that's in the primer pocket. Furthermore, the pressure of the primer far exceeds the pressure in the chamber from the powder. It's just less volume and happens a LOT faster. But again, I say it's dirt. Revolvers burn filthy, they're horrible for leaks. The dirt cakes up on those things, of course it's going to be abrasive if that crap gets blasted around.

In any case, the dirt does nearly all the wearing. And barrel heat, comes from friction. Not flame or this supposed heat in the chamber.

EDIT to add
If all that gas in there is so hot, how's come the muzzle brakes aren't glowing after you shoot a rifle. In fact, isn't a muzzle brake a damn site cooler than the barrel it is attached to after 20 or 30 consecutive rounds? Wait, it just vented nearly ALL that hot gas... I wonder how it is still cold... Damn, I'm puzzled

 

[4Mesh]

question why do 30 br bbls last over 8000 rounds and a 234/6ppc last 2000??

Mike, I'm just gonna say that "Lasting" to you and me are two different things. I've seen match barrels on a 223 last 30,000 rounds. And shoot more accurate on retirement day than the replacement. I'd say, "last" is a relative term, defined by each owner. (Most probably defined by the owners checkbook).

 

[ballpowder]

I think I was on the fence

I was not sure about this argument (discussion) until the muzzle break analogy was made. Very convincing. There just doesn't seem to be enough contact time for the heat to absorb into the steel. I'm certified welder fwiw

 

[goodgrouper]

It might interest you guys to know that I've spent literally days researching this "friction vs. temp/pressure" in regard to barrel life for my interior ballistics course and I've found contradictory information by reputable studies on both sides. However, there are many, many more sources that blame temp/pressure as the main culprit.

Here's what Sierra says:
http://www.exteriorballistics.com/reference/rifleinout.cfm


The one big nail in the coffin for the friction argument is this:
Why is there always more wear in the throat area where bullet velocity is the lowest and therefore the friction is the least?


The muzzle brake question makes sense until you realize just how much pressure and temp have dropped by the time the bullet reaches the muzzle. In some instances, it's 15% to 20% of what it was in the first few inches of the bullet's travel down the bore. In other words, there ain't much left by the time its at the muzzle brake. Then factor in the muzzle brakes own cooling properties and it's easy to see why it remains relatively cool.

 

[ab_bentley]

Well I was going to say H4198 but....... Adam

 

[4Mesh]

The one big nail in the coffin for the friction argument is this:
Why is there always more wear in the throat area where bullet velocity is the lowest and therefore the friction is the least?

Because that is where all the dirt is? Because that is the only place there is an angle into which you are crushing a bullet? Most of the wear is where most of the abrasive is.

The muzzle brake question makes sense until you realize just how much pressure and temp have dropped by the time the bullet reaches the muzzle. In some instances, it's 15% to 20% of what it was in the first few inches of the bullet's travel down the bore. In other words, there ain't much left by the time its at the muzzle brake. Then factor in the muzzle brakes own cooling properties and it's easy to see why it remains relatively cool.

Now hold the phone a minute. Temp has dropped? Was up to >zillion deg F and .000??? seconds later, it is ambient +20F? I mean, come on. So, at Mach 3, it travels 2.5 feet, and cools off. But according to some, was still hot enough at the end of the barrel to 'fire-check' it.

Ok, you guys can have your cake and eat it too. I give up.

 

[MarkR]

I suspect that he is including the unburned powder granules as well as the superheated supersonic gas that is at it's hottest at the throat area...remember...gas is a member of the friction club!
So you are saying that should a false cartridge be inserted instead of a real one, and powder residue, unburned granules and copper were shot through the barrel for a total of the same time, at the same pressure that would normally cause a barrel to wear, that the damage to the throat as well as the whole barrel would be exactly the same.

It might interest you guys to know that I've spent literally days researching this "friction vs. temp/pressure" in regard to barrel life for my interior ballistics course and I've found contradictory information by reputable studies on both sides. However, there are many, many more sources that blame temp/pressure as the main culprit.

Here's what Sierra says:
http://www.exteriorballistics.com/reference/rifleinout.cfm


The one big nail in the coffin for the friction argument is this:
Why is there always more wear in the throat area where bullet velocity is the lowest and therefore the friction is the least?


The muzzle brake question makes sense until you realize just how much pressure and temp have dropped by the time the bullet reaches the muzzle. In some instances, it's 15% to 20% of what it was in the first few inches of the bullet's travel down the bore. In other words, there ain't much left by the time its at the muzzle brake. Then factor in the muzzle brakes own cooling properties and it's easy to see why it remains relatively cool.

 

[mks]

I wonder how it is still cold... Damn, I'm puzzled

Be puzzled no more! Remember Gay-Lussac's law - the temperature of an ideal gas drops as pressure drops. The flame temperature of smokeless powder is about 3300F = 3760R. If there weren't some left over powder still burning as pressure decreased, the temperature would drop to 1R = -459F as pressure dropped to atmospheric from a peak of 60000 psi.

Cheers,
Keith

 

[4Mesh]

First of all, pressure doesn't drop to atmospheric. Muzzle pressure on a magnum firing H4831 is said to be about 6000psi. So much for dropping to 15psi. Furthermore, fire that rifle at night, and you see some flame from the barrel. Stick on a muzzle brake, and the brake will clearly show the gas is venting through the brake (as fire). But, it ain't there long, and the brake is still far cooler than the barrel. That is, in spite of having more surface area to heat, (and for the love of gawd, please dont' say it's better at radiating the heat off :rollseyes: Heard that above once already).

-459 once it reaches atmospheric pressure... Seriously? No cloud of fog? No warnings on ammo that there is a very cold gas exiting barrels? It just keeps gett'n better.

 

[thompp1]

You all might want to read up on Boyle's Law.