Gunsmithing Polishing throats to increase barrel life

[Alpine Gunworks]

I recently read some information about the 6mm Competition Match chambering. It said in a nut shell that with the use of slow burning powders, and keeping your pressures on the lower end, as well as polishing your throat every 200 to 300 rounds will increase barrel life. The slower powders makes sense since not all the powder gets burned right in the throat area, and lower pressures will help with fatique and creep in terms of the barrel material.

http://en.wikipedia.org/wiki/Creep_(deformation)

http://en.wikipedia.org/wiki/Fatigue_(material)

At a microscopic level I could see how the polishing could help prevent small cracks in the throat from getting bigger and preventing tears of the lands and so on. Does anyone here have any experience polishing the throats of chamberings that might be considered extreme in order to increase barrel life? If I was to polish the throat how far up the barrel should I polish? Please share your thoughts and experiences.

Thanks!

 

[sharpshooterbr]

I don't have any firsthand experience with this practice, but I can see the merit. I recently read an article that discussed this technique in relation to reviving a well shot 7mm RUM barrel. Check out the article at http://www.ballisticstudies.com/Resources/Articles/How+To+Break+In+a+Rifle+Barrel.html The main discussion on this technique is toward the bottom of the article.

Pretty interesting experiment. I was especially interested since I have a 7mm RUM that I shoot frequently.

 

[nashlaw]

I just finished reading some information that said the use of heavy for caliber bullets (i.e., long) and slow powders was hard on barrels. Specifically, it said for increased barrel life run the shorter, lighter bullets ((less bearing area) and faster powders.

David Tubb is a proponent of polishing the throat, and by extension the barrel, after so many rounds. I have used his Final Finish product with good results, especially on factory tubes.

I am going to do more reading.

 

[Alpine Gunworks]

Thanks Sharpshooter for that link there is some good stuff in there. I'll have to read up on Tubb's approach. As for the bullets I've read that shorter bullets cause less wear as well, and it makes sense since there would be less bearing surface. On the flip side though, copper is much softer than your barrel material and it got me thinking about heat from the powder and creep/fatique. This document I read was based around the 6mm cm which was designed to compete with the 6xc so all those guys are pushing the big heavies for long range work.

 

[nashlaw]

Alpine, go to Long Range Hunting and read the article by Mike McPherson on cartridge design and throat wear. A longer neck, according to him and others, causes powder to burn in the neck as it is thrown from one side of the case to the other as it is is directed by the angle of the shoulder. He says this action has unburned powder and hot gas impinging on the neck of the brass instead of the barrel throat.