What causes the throat to wear out faster?

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elmerdeer

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I would like to know what will cause the throat to wear out faster, Is it firing a lighter bullet with faster speed or a heavier bullet thats slower but has a longer bearing surface?
Examples; 140 accubond at 3250fps or a 160 accubond at 3000fps from a 280AI, with RL-22?
Just curious.
Elmer
 
The throat does not actually wear out due to friction,it erodes away due to a combination of heat and pressure.Regardless of the bullet weight or velocity,throat erosion depends on the amount of heat and pressure that is present in the barrel.A lower pressure reduced load will cause less throat erosion that a maximum load that produces a higher pressure.
 
It is also related to physical sandblasting by powder. Lots of powder means more erosion. Flame temperature is also a factor. 4350 erodes faster than 4831 due to flame temp. Also, there are gas eddies at the mouth of the case. A case that has been trimmed, leaving a gap to the start of the throat will casue more erosion than if cases are long.

For practical purposes, we just know that some calibers are barrel burners. If you are shooting, say, a 25-06, you might have to change your barrel every year if you do much shooting. wheras your 35 Rem can be left to the grandkids with the original barrel.
 
Size of the case affects it (bigger is worse), pressure (higher is worse) and heat (more is worse) is terrible...
 
The main factor is called slip, and it's the same as putting your thumb over a bicycle tire pump nozzle; when you activate the piston, the air escaping between your skin and the nozzle generates heat. The more heat the compression (and in a firearm, the combustion is added to it) creates the hotter will be the gases "slipping".
More powder means more heat generated in a short period and also more pressure (in relation to the bore diameter). The small diameter bullets in large capcaity cases are more prone to erosion because the phenomenom is applied to a very small surface.
 
In Answser to your question, the lighter bullet with more powder.

Regardless of which cartridge, shooting and over-heating is absolutely the worst.
 
As a rule of thumb, those cartridges having a powder charge equal to 30% of the bullet weight have optimum barrel life. The greater the powder weight from this point the shorter the barrel life. Exceptions to the rule are the small bores, in a .22 centerfire, 30-40 grs of powder produce optimum barrel life.

The rule of thumb is only useful as a comparison between the expected barrel life of various cartridges as your specific loads, shooting and cleaning habits all effect barrel life. Thus we expect that a .30/30 would have a longer barrel life than a .30-378, but you don't really need a formula to figure that out.
 
Rather than regurgitate the math, here is a link to a fellow that has quantified barrel wear based on a number of constants and from the indexes here, the formula clearly shows that is is accurate.

ht tp://ninthstage.com/index.php/2008/05/06/overbore/

You will note that predictably, magnum cartridges have high OBI's but pay particular attention to the 50BMG. It has a huge overbore index and as such is guilty of being a huge barrel-burner, but then if you can afford to shoot one, the cost of a re-barrel probably isn't an issue.

furthermore, the point to which I previously alluded, is that shooter input still plays a huge role in barrel (throat) life.
 
Obtunded said:
Rather than regurgitate the math, here is a link to a fellow that has quantified barrel wear based on a number of constants and from the indexes here, the formula clearly shows that is is accurate.

ht tp://ninthstage.com/index.php/2008/05/06/overbore/

You will note that predictably, magnum cartridges have high OBI's but pay particular attention to the 50BMG. It has a huge overbore index and as such is guilty of being a huge barrel-burner, but then if you can afford to shoot one, the cost of a re-barrel probably isn't an issue.

furthermore, the point to which I previously alluded, is that shooter input still plays a huge role in barrel (throat) life.
Click to expand...

Link Fixed

http://ninthstage.com/index.php/2008/05/06/overbore/
 
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