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Barrel Wearout

05 Dec 2013
@ 03:11 am (GMT)

Roy Murry


I am a research consultant working with a nanotechnology tribology (the study of friction) start up in The States, Eastern Washington to be specific. We are developing a product which can coat the bore of a firearm and induce various beneficial properties, including extending the service life, eliminating micro pitting from the manufacturing process and others. If you want to know more feel free to ask, but I'm not posting to advertise.

What I'm trying to identify is a type of rifle which has a relatively short barrel life as a stock weapon. I've heard most of the 7mm family tend to be hard on barrels; 7mm Rem Ultra and 7mm WSM specifically. Does anyone have experience with this? If we can find a rifle that will suffer barrel wearout in several hundred rounds, we can very easily validate or disprove some of our theories.




05 Dec 2013
@ 02:24 pm (GMT)

Nathan Foster

Re: Barrel Wearout
Hi Roy, the 7mm RUM is a good choice because it is currently very popular and so would attract plenty of attention if you are successful in your endeavors. You would be able to use the rifle for marketing purposes as a common point of reference.

Barrel life of the RUM and other over bore cartridges is very much depended on how the throat is cared for (gas erosion) which is why you will find such varying opinions as to barrel life. Generally speaking, with traditional barrel care (basic cleaning and oiling), accuracy tends to wane between 400 to 600 rounds based on my own testing along with reader feedback. I generally recommend abrasive polishing to keep the pores of the steel closed as per the barrel break in article of this site. The reader or client is asked to consider which is worse- abrasive polishing or leaving the barrel untouched, allowing the cartridge to gas gut the throat, eventually leading to severe erosion in overbore cartridges.

Employing a coating system raises questions as to how to go about maintaining the throat long term. A coating cannot prevent high temperatures and if you have engineering experience, you will understand that high heat is what opens the pores of the steel at the throat, causing what an engineer / sheet metal worker would call a "heat affected area". So there are many issues you will need to explore.

To test performance, you will need to develop an accurate load and test this load several times to make sure accuracy is repeatable. Following this, you will need to steadily shoot and work towards the 600 round mark, occasionally testing the rifle for accuracy as you go. Then attempt to work to 900 rounds. 900 rounds is the goal, 1200 rounds would be excellent. Light bullets and high powder charges speed erosion however you will probably want to work with a 160-180gr bullet so that you can develop an accurate load. Goal accuracy would be less than .5"

It will take about two weeks to reach 600 rounds if you work diligently, taking checks into consideration. Providing the rifle is accurate, the condition of the bore is not of great concern, only the throat. However, if a brake is employed, you will have to watch for carbon caking (from some blow back and or condensation) towards the muzzle. After load work, you will have to try and mimmick typical field usage, not getting the barrel too hot, yet not shooting fully cool groups either. Shoot till warm then cool, shoot till warm, then cool- and so forth. Depending on barrel contour, you may find that this basically involves 3 steady shots, then cool.

The 6.5 Lapua Magnum would be another option for testing but as this is not common, it may not be useful as a point of reference.

I don't normally engage in matters of a professional nature such as this on our forums. If you need more help, please contact me directly.

Hope that helps, Nathan.
05 Dec 2013
@ 08:00 pm (GMT)

Jim Moseley

Re: Barrel Wearout
Great topic. Hope to hear more! Always something to learn.
05 Dec 2013
@ 11:15 pm (GMT)

Martin Taylor

Re: Barrel Wearout
Roy this is a great topic!

And as Nathan has said there is no clear answer only general rules of thumb!
People veiw cleaning/care in very different ways, little to no cleaning, some only use light solvents with nylon brushes others carbon & copper removers with stiff bristel brushes.
Then their are others who lap & polish their bores only while new during run in. And still others that continue to polish through out the barrels life.
And before all that you start with running in procedures (or lack of), so l dont believe there is a one size fits all for this topic!

But as l said great topic,

Good luck Marty
12 Dec 2013
@ 05:22 pm (GMT)

Roy Murry

Re: Barrel Wearout

Nathan - Roger that, I'll contact you offline.

Thanks Jim!

Marty - This has been a source of debate within the team. Since we're looking at doing such a long run, the slightest variance will likely have some effect. Thus, I'm likely to opt for the minimum. Regardless of the amount of cleaning and care, what we're looking fr is a bottom line % increase in longevity until accuracy degradation. The initial test being only two barrels, one can hardly consider it scientific. Thus, future tests will probably be done in pairs as well, with different sets of identical variables.




We are a small, family run business, based out of Taranaki, New Zealand, who specialize in cartridge research and testing, and rifle accurizing.