QUESTION - BREAK IN A BARREL:
What is your ideas on breaking in a barrel?
I will let Gale McMillan, one of the great barrel makers, answer that: "Consider this: every round shot in breaking-in a barrel is one round off the life of said rifle barrel. No one has ever told me the physical reason of what happens during break-in firing. In other words what, to the number of pounds of powder shot at any given pressure, is the life of the barrel. No one has ever explained what is being accomplished by shooting and cleaning in any prescribed method. Start your barrel off with 5 rounds and clean it thoroughly and do it again. Nev Maden, a friend down under that my brother taught to make barrels was the one who came up with the [one shot one clean] break-in method. He may think he has come upon something, or he has come up with another way to sell barrels. I feel that the first shot out of a barrel is its best and every one after that deteriorates [the bore] until the barrel is gone. If some one can explain what physically takes place during break-in to modify the barrel then I may change my mind. As the physical properties of a barrel don't change because of the break-in procedures it means it's all hog wash. I am open to any suggestions that can be documented otherwise if it is just someone's opinion--forget it.
It all got started when a barrel maker that I know started putting break-in instructions in the box with each barrel he shipped a few years ago. I asked him how he figured it would help and his reply was "if they shoot 100 rounds breaking in this barrel that's total life is 3000 rounds and I make 1000 barrels a year just figure how many more barrels I will get to make." He had a point; it definately will shorten the barrel life. I have been a barrel maker a fair amount of time and my barrels have set and reset benchrest world records so many times I quit keeping track (at one time they held 7 at one time) along with High Power, Silhouette, Smallbore national and world records and my instructions were to clean as often as possible preferably every 10 rounds. I inspect every barrel taken off and every new barrel before it is shipped with a bore scope and I will tell you all that I see far more barrels ruined by cleaning rods than I see worn out from normal wear and tear. I am even reading about people recommending breaking-in pistols. As if it will help their shooting ability or the guns".
QUESTION - DOUBLE RIFLES:
With conventional monometal solids, grooved solids and jacketed lead solids, the displaced material is compressed into the shaft of the bullet under great pressure.
It is also important to note that our bullets are manufactured from copper. Many monometallic bullets are made from harder materials such as bronze alloys and the manufacturers themselves warn against the use of their bullets in doubles. Some bronze alloys actually approach the tensile strength values of the barrel steels of older doubles.
A bullet only needs to be as hard as is required to prevent failure after impact. The FN bullet in the first picture at the top, was recovered from the earth after an insurance shot, fully penetrating a downed elephant. The picture below is from an internet discussion forum and is a GS Custom .474 500 grain FN fired into an elephant shoulder at a little more than 2300 fps. It passed through the bone and gave a total of 6.5 feet of penetration.
Clearly, GS Custom bullets are hard enough for any job at hand and any bullet that is harder, will simply result in more barrel wear without any additional benefits.
Should your double rifle or other firearm have an unusual bore / groove configuration, we can make special run bullets to suit the bore of your rifle exactly. There is no extra charge for this service.
QUESTION - FLAME EROSION OF THE THROAT:
With the extra speed that can be obtained with HV and FN bullets, how is flame cutting of the throat of the barrel affected?
Throat erosion is accelerated by increased pressure and temperature. The scenario effectively feeds on itself in the sense that elevating pressure will have a tendency to raise temperature as well. With HV and FN bullets extra speed is obtained without elevating pressure beyond normal levels. The drive bands make entry of the bullet into the bore very light. HV, SP and FN bullets are manufactured at barrel bore diameter and only the drive bands are at barrel groove diameter giving a good gas seal with no blow by of gas.
As the pressure curve rises, the expanding volume behind the accelerating HV/FN bullet increases much quicker than with smooth or grooved bullets. Smooth and grooved bullets have nose shapes that terminate at barrel groove diameter and the last section of ogive and the first portion of the shank are much harder to engrave than the thin drive bands on HV and FN bullets.
The advantage of this is that with HV/FN bullets, the pressure curve peaks further down the bore and the initial temperature spike is distributed over almost three times the surface area of barrel, compared to smooth and grooved bullets. The throat runs cooler and lasts longer.
It is possible to mimic the features of HV/FN bullets with grooved and smooth monometallic bullets. By manufacturing a monometallic bullet that is undersize for the barrel, engraving force is lowered and the gas blowing past between the barrel wall and the bullet, acts as a relief valve to slow the rise of the pressure curve. This also requires more powder to be used due to the loss in pressure. The increased powder charge sustains the pressure curve rise for a longer period, accelerating the bullet to a higher speed at the muzzle. The price for this is paid eventually in drastically reduced throat life and the resultant loss in accuracy that follows.
If a recovered bullet is examined, it is easy to determine whether the bullet sealed the barrel properly or not. See the pictures below for examples of this. Bullets can also be measured and compared to the CIP and SAAMI data available here.
Below is a relatively extreme example of an under size bullet. Note how the material that was displaced by the rifling flowed into the space between the surfaces of the bullet and the barrel. Gas cutting with such a combination will be accelerated due to the ineffective seal.
It is clear that gas jetting past a bullet, as it accelerates down the barrel of a rifle, must be avoided. Sooner or later the shooter will pay the price in the form of gas erosion. Accuracy reduces and the barrel has to be replaced.
QUESTION ON BULLET COATING:
Even with conventional moly-coating, there is no problem if it is done right.
The item below is from the http://www.6mmbr.com website.
MOLY -- Does It Extend Barrel Life?
Norma Tests Show Moly Reduces Throat Erosion Significantly
The enormous forces that build up in rifle barrels cause severe wear to lands and grooves. Here is a close-up of the throat wear in three different 6.5x55 barrels. These Norma test photos show wear after 10,000 shots with Norma Diamond Line "Bana", after 3,700 shots with uncoated bullets, and after 7,000 shots with Diamond Line Fält.
Compare the results for yourself. Norma claims "testing showed barrels retained accuracy more than twice as long when Norma moly bullets were used from the outset. This is because Norma Diamond Line is coated with molybdenum disulphide and a protective layer of wax. Friction is reduced which means that the bullet travels further along the barrel before peak pressure is reached. The result is lower wear and improved accuracy".
See some more facts about moly coating