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Old February 24, 2007, 04:24 PM   #1
Ammo Junky
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Ball powders, does it give longer bbl life?

I tipicaly use ball powders in pistol and stick in rifles. Does anyone know of a legitimat test of the two in regards to rifle bbl life?
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Old February 24, 2007, 04:38 PM   #2
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Powder type has almost nothing to do with barrel life.

Pressures contained within the barrel during firing have everything to do with barrel life.
If you wish more information on this pm me. It has been discussed many times.

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Old February 25, 2007, 03:12 AM   #3
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ditto
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Old February 25, 2007, 09:14 AM   #4
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Well, I disagree. It ain't pressure that kills a barrel it's heat. Pressure is a good indicator of the heat being generated. Back to the original question. The type of powder doesn't matter.
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Old February 25, 2007, 10:21 AM   #5
Art Eatman
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In the early days of development and use of the M16, the original design called for IMR powder. Olin lobbied the Pentagon, and ball powder became the standard use.

The change in powder increased the rate of fire on full-auto. I have read that ball powder burns somewhat hotter than IMR. (Which was true of the old Hercules HiVel powders; single-based vs. the IMR double-based.)

A hotter-buirning powder will erode the leade at a somewhat lesser number of rounds. There is some effect, also, from rate of fire and not letting the barrel cool between shots or strings of shots.

As a generality, rapiid erosion of the leade is no particular problem for muzzle velocities around 3,000 ft/sec or less. It begins to be a problem, as near as I can tell from reading, for muzzle velocities in the range of 3,300 to 3,400 ft/sec and above. Roughly.

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Old February 25, 2007, 01:40 PM   #6
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The main problem with the ball powder in the M16 was one of calcium carbonate fouling. Upwards 1.25% CaCO3 was added in the final stages of powder production to neutralize any acids left over from manufacture.

On firing, it would collect in the gas system and essentially form "stones" that were difficult to remove even with the proper cleaning tools, and this was the cause of a LOT of the early functionality problems with the M16.

Winchester later determined that no more than 0.25% CaCO3 was needed to effectively neutralize remaining acid, and at this level, there's not enough to form accretions in the gas system.

In general, the hottest burning powders tend to be those that are double-based, using both nitrocellulose AND nitroglycerine.

In the old days, when gun steels were softer, this could cause lots of problems.

It did, especially for the British. Cordite was a double based powder and was notorious for burning the lead out of many early .303s.

Even today you can find old Lee Enfields that look like muskets for the first 2 or so inches where the rifling use to be.

This was also a problem with British naval guns, which also used cordite propellant.
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Old February 25, 2007, 02:28 PM   #7
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Quote:
single-based vs. the IMR double-based.)
Art, are you sure of that statement? I have never heard that ANY of the IMR powders are double based. The old Hercules reloader lines, and the present Alliant ARE double based.

While I don't believe it, Vitivouri claims that their powders burn "cooler". In order to get pressure, you need heat, you can't get pressure without heat, so just how does one powder burn cooler than another,,,as long as they both have the same burning rate!?

To avoid/limit throat erosion, go with the slowest velocity, with the slowest burn rate powder that provides the accuracy you desire.
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Old February 25, 2007, 02:52 PM   #8
Jim Watson
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Art's got it just backwards. IMR powders are single base, all nitrocellulose. The old Hercules powders were double base, nitrocellulose plus nitroglycerine. It didn't get that way by accident, the trust-busters required DuPont to break up their monopoly. They were allowed to keep some gunpowder business and elected to specialize in single base. Hercules got the double base line of the day and its successors. Many years later, DuPont (now IMR Powders) added back 700X and 800X double base. Alliant bought out the Hercules powders and added more, but the Reloders are imported.

Bruce Hodgdon always claimed his "Spherical" (originally surplus Ball powder) gave longer barrel life, but later testers say not.
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Old February 25, 2007, 06:08 PM   #9
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Well, I disagree. It ain't pressure that kills a barrel it's heat. Pressure is a good indicator of the heat being generated. Back to the original question. The type of powder doesn't matter.

Well,let's see what the majority thinks.

The quote below is part of a larger article. If anyone wants the entire article it's at..
www.chop45.net/phpBB3/viewtopic.php?f=117&t=904


Throat CORROSION

From this point on I am espousing theories put forth by M.L. McPherson in a series of articles published in The Varmint Hunter Magazine. Some of his analysis is technically above my head, the rest makes emminent sense.

Mic McPherson is a gun nut with deep credentials, an accomplished bench rest shooter and long range varmint hunter. He is also part of a pair that have developed the SM^2 line of cartridges in a quest for more efficient combustion of charge. The notable feature of the design is a patented hemispherical shoulder, the benefits of which...I'm uncertain. Along the path to developing the design Mr. Mic had a few detours and discovered(?) a few things. I say discovered only because I'm unaware of any other research so pointed in regards to throat erosion, or more properly CORROSION.

What he did is this. A test rifle equipped with temperature sensors and an external calibrated Infra Red camera were used in tandem to measure barrel temperature over the length of the barrel, and close track of time was kept as well. What he found was rather interesting, and it is quite contrary to conventional wisdom. The reasons for this I'll discuss shortly, but the nut of it is that barrels heat up not because of powder burn, but because of the mechanical stretching imposed by pressure generated by the burning of the powder charge. The surface temperature rise is too rapid to result from heat transfer, surface temperatures rising almost immediately after firing for the length of the barrel. Heat transfer would not, cannot act so rapidly. Further, the rise in barrel temperature carries only to a given level then stabilizes during sustained fire. Do understand this evaluation came from a sporting rifle, not a machinegun. I'm not certain what difference that would make anyway, but in any case while doing sustained fire evals the rate was fairly aggressive for a sporting rifle and the temperature at which the barrel exterior stabilized was such that it would not significantly contribute to a meaningful quantitative increase of interior temperatures and contribute to erosion attributable to heat or ionization.

What he has to say on the matter is summed up as follows: When a barrel suffers the rise in pressure that follows ignition it yeilds to the pressure. It expands. Steel is elastic. The pressure is contained by the barrel and the bullet which begins to migrate down range. This mechanical stretching is in effect much as you'd see in a Saturday morning cartoon where the barrel swells and that swelling follows the bullet or shot down the barrel of Elmer Fudd's gun. The amount of this action is proportional to pressure at any given point down the bore and thus the heat generated by this stress is proportional as well. Bend a coat hanger until it breaks then have your wife quickly grab the broken end with one thumb and forefinger and a point about 3" from the break with the other thumb and forefinger...simultaneously. Hand 'A' will react very quickly(time to duck) and this illustrates the point of stress generating heat nicely I think. Well you say, it is still caused by heat, this erosion thing! Sorry, not in Mic McPherson's world or mine.

When the barrel swells, most notably in the throat region, the mass of the barrel in cross section does not change. Only the dimensions change. Something has to give and it does, the interior of the barrel cracks in a very small way, but it cracks nonetheless. Heat does NOT cause metal to crack, stress does however when the displacement exceeds yield stength of the alloy. Very fine cracks they are, but cracks in any case. They are commonly viewed in pictures taken during bore scope investigations, the fine alligator hide apperance not unlike Cindy Sheehan's face. And what happens then? Well, here's the good part. The byproducts of powder burn are forced into these voids and the forces of stress and chemical action begin their work.

What is this 'corrosion' crap yer talkin' about Dan? We're talking about throat erosion ain't we? In a word, no. Erosion is the product of mechanical abrasion be it from gas, fluids or solids. It creates smooth surfaces even if irregular in form. A look thru a bore scope should be enough to dissuade one from assigning that context to what I speak about. There are a number of byproducts of the burning of gun powder. They differ between black and smokless but for sake of this discussion such differences are of no importance. I could if I desired let you in on the chemical reactions and pontificate at some length. Better you Google it up and ponder on your own. Three culprits from the burn of smokeless powder are of interest here. One is Hydrogen in gaseous form. Its presence leads to hydrogen embrittlement, a hardening of the metal that begins with the first shot from any barrel, regardless of cartridge. The significance is that the thin layer of metal that faces the wrath of our powder's burn becomes infused with hydrogen and thus hardens slightly, and that contributes substantially to the fine microscopic fractures I mentioned earlier. Hard metal cracks more readily that soft. eek Next is nitrogen in various chemical forms I cannot elucidate on in any meaningful way. Suffice it to say they are corrosive to some degree and with each shot they are laid down in the fractures. This residue cannot be removed by cleaning within the confines of the fracture zone(s). Thirdly in carbon. It too builds up in the fracture zones and while not corrosive it is very hard and again, within the fractures largely immune to removal. Carbon in this context is nearly as hard as diamonds, and when wedged into the fissures is does not allow them to close, not even a little. The net thrust of all of this is that with each shot the matter becomes more compounded, it is irreversable and....your throat metal begins to do some really odd things. For one, as the process proceeds the interior diameter of your bore gets smaller. I know that in contrary to the idea of erosion, but not that of corrosion. It's effects are simple. The cycle of fractures and addition of combustion byproducts and corrosive byproducts is cumulative. It adds mass and something has to happen to allow for this growth. It is easier for the barrel interior to 'grow' than the thicker and more profound mass of the exterior, and grow it does, choking down the diameter of your bore. What this does is swage your jacketed bullet down a bit. It does so at a point where maximum pressures are experienced and logically the pressure diminish after the fact, AND THOSE PRESSURES ARE INSUFFICIENT TO CAUSE THE BULLET TO OBTURATE A SECOND TIME. There goes accuracy out the window. crybaby It is my opinion that the conventional course chosen to remedy this, setting the barrel back and cleaning up the throat, remedies the issue not because of the clean up, but because it moves the choked area of the throat deeper into the high pressure region of the barrel and thus allows the bullet to obturate once more. It is also my opinion that a reason that fire lapping restores accuracy to burned out throats has to do with removal of some if not all of the choked portions of the throat. I assign this action as a pallative, not a cure. The reasons they cure the problems to some degree if not completely are my speculation. The previously discussed dimensional chages are not speculation but rather have been measured and documented.

The next point I'll make for this case is that as the process continues, both the fracturing process and corrosion, the roughness of the bore grows exponentially. It continues to the point in well advanced cases that small pieces of the bore metal will be ejected from shot to shot. It is a circumstance of destruction that gains momentum as it progresses, and have been documented a myriad of times by bore scope inspection.

In summary, if you've gleaned some perspective from what I've written it likely is that 'barrel burners' are cartridges that generate high peak pressures and are generally of the low expansion ratio persuasion. That understanding is correct. The Swift, the 7mm STW, the .243 Win., in short those cartridges that generate high pressures. Throat 'erosion' is their domain without exception. There is a direct correlation between rifles that experience this and chamber pressure, both in terms of proportionality to peak pressures and location of 'erosion' in regards the shape of the pressure curve, ie. where the bullet is at the point of peak pressure. At present we have no metallurgy that will withstand the forces involved AND provide guilt edge accuracy(sorry, Stellite inserts fail in the latter), so we have to accept the fact IF we are disposed to shoot rifles with cartridges that generate high pressures. How high? There is a proportional relationship between pressure and this issue, and at some point it becomes a non-issue. Precisely where I cannot say. In crude terms the effects increase dramatically above 50 KPSI, perhaps even on an exponential level above 60 KPSI. Those cartridge/rifle combinations that live below 50 KPSI are far better, whether by SAAMI spec. or by your handloading approach. If you keep the pressures down your rifle will live longer, in some cases a lot longer. When one drops down to the realm of .30-30 class pressures(40-45 KPSI) it is something you are unlikely to live long enough to experience with a given gun, all else being equal. It's all about the pressure.......
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Old February 25, 2007, 08:07 PM   #10
Ammo Junky
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Thanks Old Fox, I never heard it explained that way before.
AJ
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Old February 25, 2007, 09:24 PM   #11
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I stand corrected.

I have personally inspected bores but they were of a much larger size. like 5". the effects are dramatic.
I didn't think those guns generated that kind of pressure but further thought tells me it must.

I wasn't into that end of it. all I did was supply muscle to change the barrels after we determined it was time. The barrels were then shipped out for further inspection and such. Barrel testing is hard work.
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