This subject (throat erosion) gets me to thinking. I have to agree that more barrels are ruined by neglect than any other reason. Either they are cleaned improperly damaging the throat or the crown. At the other end of the spectrum - not cleaned at all and moisture collects under the powder residue and corrodes the barrel, pitting it up. The average hunting rifle, especially magnums are not shot that much. I could be wrong on this, but I say the higher the kick, the less they are shot, in most cases. A 300 Win Magnum more than likely will not get 1K rounds put through it in 2 life times. The average hunter mounts a scope and zeros it in, using maybe 20-25 shots to zero the scope and try a couple of different loads. If he reloads the count will go up trying to develop a load, maybe 200 rounds. After that he will shoot maybe 10 rounds a year to check zero and shoot maybe 2-3 shots during season. After the initial year, he more than likely will only check zero and foul his barrel for the season and again shoot maybe 2-3 shots during season. Some do not even do that, they just pick up the rifle for hunting season and shoot at game. It will take a lot of years to accumulate 1K rounds. I have known some hunters that have bought 2 boxes of ammo and they are still shooting out of it after 5 years. So I agree that most barrels are not shot out, they are ruined due to poor clean techniques or not cleaning at all.
I am not an expert on internal ballistics, but I do have engineering background. I respectfully submit, that unburnt powder going through a throat causes more damage, than the heat generated or gas cutting by the passing of gases. I make one premise - not all the powder is burnt before it reaches the case mouth. Some of it gets pushed out the case mouth before it is burnt, since it burns from the back to the front. I do not think it gets totally burnt up until it gets a few inches into the barrel. Higher volume of powder + high pressure cartridges do this more that low volume, low pressure cartridges. Does hot gases, cause throat erosion? I think with out a doubt, but I also think that the unburnt powder going through a throat at high pressure causes much more of the erosion than does the hot gases. I do not think that any one would dispute that a 300 Win Mag will erode a throat much quicker than a 30-30. Why? Because the gases in a 300 Win mag are hotter than a the gases out of a 30-30? I do not think so. I think it is the powder that is yet unburnt at high pressure that causes friction that erodes a throat. I think that 35 grains of powder going through a throat at a pressure of 40 psi has less unburnt powder going through a throat than a 300 Win Mag with 75 grains of powder with a pressure of 60 psi. Are the gases of the 30-30 cooler that the gases of a 300 Win Mag? We are talking milliseconds of exposure of the gases to the throat. How much heat can be transferred to the barrel during this time? Wouldn't the 30-30 gases going at a slower rate than a 300 Win Mag be going slower and expose the throat for a longer time to the heat of the gases? No doubt there is some heat transfer and gas cutting, but I do not think it is enough to heat up a barrel or wear away a throat a whole lot. Enough that the very surface is heated up, but not enough to dissipate throughout the barrel volume. I say it is the volume of unburnt powder and it's pressure against the throat/barrel that really does the majority of erosion in a throat. An extreme example - Think of a sand blast against a metal surface and a cutting torch on a metal surface. Now pass both over the surface quickly. Which one is going to erode metal more? Is the metal going to heat up more due to the quick pass of the torch or from the friction of the sand blast? You will find that the sand blast will remove more metal and heat it up due to friction more that the cutting torch. Small necks and high powder volume exposes the throat for longer amount of time to unburnt powder at higher pressures that a low volume powder at lower pressure going through the same size hole. Even though the throat is exposed to the hot gases the same amount of time or longer in the low volume case, the barrel will experience less heat build up and less throat erosion.
Like I said, I am not expert, I just have logically thought this through. So I may be totally wrong here, but I really do not think so. Think about it.
