Barrel wear. Caused by Pressure?

[Ray B]

If two cartridges, one a .224" (220 Swift for example) and the other a .458" (458 Win Mag) are loaded to equal pressures, 60,000 psi the 22 will send a bullet from case to muzzle in about .001 second while the 45 will have about double the time in the bore. Since the 45 bore would be exposed to the same pressure but for twice as long, why does the 22 barrel burn out twice as fast as the 45?

 

[hpshooter]

"Since the 45 bore would be exposed to the same pressure but for twice as long, why does the 22 barrel burn out twice as fast as the 45"

I do not have the knowledge to know what the relative barrel lives would actually be.
This is a baited question since it opens the door to the concepts of volume, pressure and velocity. Realizing that, I will venture into the swamp.

With regard to the wear rate in the throat of the barrels it is my belief that the higher velocity of the gas in the .224 bore is the cause of the accelerated wear over the larger bore.

What is missing in this scenario is the volume of 60,000 PSI gas each cartridge produces and how long it is moving through the throat and barrel to cause erosion and gas cutting. The pressure does not remain at 60,000PSI for the entire barrel dwell time and the pressure will drop faster in the large bore due to the fact that the big slug opens up more area for the gas to occupy as it moves down the barrel.

My barn yard evaluation.
Hog, fire up the popcorn popper!

 

[Lapua40X]

https://gunsmagazine.com/rifle-barrel-burn-out/

 

[MrBottleneck]

Well, being I am not the most studied fellow in the study off barrel wear I will go with heat.
That 220 is going roughly 2200 fps faster.
Using most general load data the 220 is going to be loaded with a lot hotter burning powder to achieve the higher velocities.
Here is some serious technical reading for you regarding barrel wear.
http://www.dtic.mil/dtic/tr/fulltext/u2/a440938.pdf

 

[JohnKielly]

I hear that what you should consider in the first instance (there are a number of issues that might be involved is the circumference of the hole in the barrel compared with the heat that you're squirting down it.

 

[ebb]

The 458 bore has way more square inches of surface area than the 22 bore and the heat is dissipated over probably 3 times the area.

 

[joshb]

This^^^^^^^^^^^^^^^^^^^ Well put, ebb.

 

[mikecr]

Should drop the term 'wear' and consider erosion(if that's a problem for you) and/or bore constriction (the ultimate killer).
Pressure just contributes to heat.
Any of us could burn out any bore in one range session if we go all Nazi behind it..

 

[MrBottleneck]

Ray, (and others who like reading)I thought I would also share this older article. Its an interesting read as well.

 

[dcali]

Barrel wear is horribly complicated and has much to do with things other than pressure and time, but I would suspect that a major factor here would be that the .45 has about twice the surface area available to absorb the energy. It would also not surprise me to find that the 4x increase in bore volume plays a role.

 

[Ray B]

Thanks for the replies. I can see that the forces that cause barrel erosion would be of similar severity (given similar chamber/leade/barrel dimensions) for a .224" bullet being pushed to 4000 fps compared to a .458" bullet being pushed to 3000 fps- the main difference being that very few people are going to take a 460 Wby out for an afternoon of prairie dogs and burn a hundred rounds.

 

[mikecr]

No, you didn't get it at all..

 

[Ray B]

Anyone that goes "all Nazi" has NOTHING relevant to say on any topic.

 

[tripdad]

So im no expert but believe i can explain it in laymans term so everyone can understand then someone thay really know can tell ypu and me if im correct. Think water hose in the yard, you have lose dirt and say 60psi water pressure, will go with multiples of calber sugested. One hose is 4.58 inches, and one is 2.24 inches. Squirt the lose dirt with esch, the same pressure comes out smaller hose faster so it erodes dirt faster, same as the gas coming out of the case does to the barrel. If im wrong please let me know, this is how i think it works.

 

[mikecr]

Except, the water is not continuous, but in various spurt rates, peaking in velocity & pressure different distances down a hose, and it is cleaner or dirtier, and hotter or colder.
No single adage would pass tests as the cause, because their are multiple causes.

 

[Syncrowave]

Fire cracking might be caused by pressure, but my hunch is that most of the throat erosion happens when there is a tiny space between the bullet and the throat, and the hot high-pressure gas erodes the steel, just as high-pressure steam (or water) erodes a crack in a pipe (or a river bed).

Since the 458 has about double the circumference of the 224 (oh and no shoulder constriction), and a much heavier barrel and therefore more thermal mass, and lower velocity, and and and and – the 224 is gonna erode faster.