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Barrel breakin

 
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  #15  
Old 03-04-2007, 02:58 PM
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Join Date: Aug 2003
Location: McKinney TX
Posts: 403
Re: Barrel breakin

[ QUOTE ]

Factory barrels are a waste to spend any of that time.


[/ QUOTE ]

Roll-Yur-Own,

Not always so and with a as little as $75.00 some can be made tack drivers. I bought a Left-handed Winchester Model 70 Featherweight in 300 WSM. BTW my new nick name for this rifle is the ďMuleĒ. Can anyone guess why?

Anyhow, it would put the first two rounds in about an inch at 100 yards and throw the third shot left by 2 or 3 inches. After shooting custom guns for the last 10 years I was having a hard time accepting that type of accuracy. This was after I glass bedded the action and the first 1Ē of the barrel and spent $40.00 on a crisp 2 pound trigger job.

I sent the rifle to my favorite gunsmith to hand lap the factory barrel hoping that would work and I would avoid an expensive re-barrel job. My smith charged me $30.00 to hand lap the barrel.

He said the barrel was typical factory and had a lot of rough patches, but said it lapped out well. Now it was off to the range. Once I got it sighted I shot a 3-group just to see what it would do. It put the 3-shots in a nice .667Ē group @ 100 yards. After a couple of hours of shooting other rifles I gave it another 3-shot group. This one measured .710Ē @ 100 yards. BTW I was shooting Fed Premium 180 gr Barnes Triple shock factory ammo.

For a 7.5 pound lightweight hunting rifle with scope, thatís alright with me. For less than $75.00 itís a hell of a good shooting hunting rifle.

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Mathew 5:16

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  #16  
Old 03-04-2007, 07:40 PM
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Join Date: Jan 2007
Location: PA
Posts: 1,067
Re: Barrel breakin

Check this out at Krieger's web site. No fdiscussion of moly, but good cleaning instructions:

http://www.kriegerbarrels.com/RapidCat/c...;CompanyId=1246
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  #17  
Old 03-04-2007, 11:42 PM
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Join Date: Jun 2006
Location: Memphis, TN. Soon to be Casper, WY.
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Re: Barrel breakin

Jeff,
I was reading on the Norma site where they showed pictures of 3 rifle barrels that were sectioned. (Here is the site: http://www.norma.cc/sida/eng/index.html then click on Target, DiamondLine and Barrels retain accuracy...) One barrel has 3700 rounds and is worn badly, another has 7000 rounds and not much wear showing, the 3rd has 10000 rounds. Norma says that 2 of their 6.5X55 barrels got more than twice the number of accurate rounds shooting mollyed bullets than their barrel that shot uncoated bullets.

My question is why this seems to work for them?
How come they did't get the molly build up in front of the chamber that destroyed your barrel?
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  #18  
Old 03-05-2007, 07:52 AM
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Join Date: Aug 2003
Location: McKinney TX
Posts: 403
Re: Barrel breakin

First Iím no expert, just someone who ruined a new barrel. Being an engineer and one stubborn SOB I couldnít let go until I uncovered the answers and understood what had happened and how to prevent it a second time. I learned a lot along the way. I donít have all the answers. Some folks swear by moly and love the stuff. I saw first hand the damage that could be done with the stuff and enough barrels at Speedyís that were ruined by it to stay clear. I then went on the hunt to find out why.


Like I mentioned in one of the earlier posts, claims can be very narrowly focused. The three photos on the Norma site donít give a lot a detail, only to say itís in front of the chamber. Is it showing the entire throat area, the middle or end portion of the throat or just the lands and grooves after the throat? Also a good cleaning job, specific barrel location and a magnified picture would reveal a lot more information. What is their criteria for loss of accuracy and why?

However if it is the throat section, the barrel with 10000 rounds looks the worst with black build up, almost twice that of the one with the 3700 rounds. But again there is not enough detail or information to gain a true perspective.


There is little doubt in my mind due to lubricant properties of Moly that I think it could help extend the life of the lands and grooves in a barrel. However, one thing that you cannot escape is damage to the throat whether youíre shooting moly or uncoated bullets. Over a number of rounds and itís different for each caliber, the excess heat and pressure from the round going off will start to erode and stress crack the throat area. It will also push the throat out. Moly coated bullets are not going to stop this erosion. A .220 swift and a .300 win mags are famous for burning up a barrel in as little as 1000 rounds, while .308 may go 3000 to 6000 rounds. This is one reason you see people re-chambering there barrel to push the throat out. The lands and grooves are usually fine, but the throat section is toast.

Norma is stating that they get longer barrel life due to less friction and pressure, which again I would agree with for prolonging the lands and grooves. Moly is not going to significantly reduce the pressure from the round going off to save the throat area. Meaning the pressure of a normal .308 round going off is around 53,000 PSI. How much lower is a moly coated bullet going to reduce the pressure in the throat section of the barrel that would make it last 3 times longer. Certainly itís going to reduce the pressure to 17,666 PSIís or one third that of 53,000 PSI


As for your real question, I donít really know, not enough detail or information from the picture.
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Mathew 5:16

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  #19  
Old 03-05-2007, 04:56 PM
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Join Date: Mar 2007
Posts: 81
Not all moly is the same!

Molybdenum disulfide is not chemically neutral, and under such intense pressure and heat, with moisture present (even atmospheric) it can produce sulferic acid. If ever there were a chemical agent that would be bad for even the most corrosion resistant stainless, that's it.

Certain high quality manufacturers have attempted, with varying degrees of success (Some high, as I'm told, unfortunately I have no names ;-(... ) to stabelize the moly without harming its effects.

Others have tried tungsten disulfide. Even slicker than moly, and it can be applied with very exact thickness. I don't know how it's working out, but it sounds promising.

Finally, I still believe that a bore coating is the answer, rather than a bullet coating. I have a propane fired forge and a great deal of abrasives, and so in the near future I will be testing the effects of several different commercially available dry film lubricants and other such treatments to see weather they will offer any resistance to carburization and abrasion. If those tests turn out to be promising, I will run tests by burying tabs of treated and untreated steel in some smokeless powder and lighting it off to see if there's a difference.

If I get something that can protect against all 3 tests better than the bare stainless substrate, I'll be sure to test it in a real rifle barrel. I have a ruger #1 in .243 Win that I want to rebarrel when the factory one is done for, so that one is up for the chop
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  #20  
Old 03-05-2007, 06:21 PM
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Join Date: Sep 2002
Location: Illinois
Posts: 836
Re: Barrel breakin

Jeff,
Sorry you wrecked a barrel. I've used Necco moly for years and have never had a problem in any caliber but only shoot maybe a thousand rounds a year between a dozen rifles. I rarely use a brush and my "break in" is "patching" a new custom barrel until clean and dry and then burnishing in an alcohol moly mix. Then begins the loading process. I also have a 15X medical grade bore scope but have never seen the moly build up in the throat area you describe. Do you think you could post some pics of this ring or leave a link where some are posted? I also never wax these bullets after coating. Waxing may contribute to the problem you describe.
db
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  #21  
Old 03-05-2007, 07:08 PM
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Join Date: Aug 2003
Location: McKinney TX
Posts: 403
Re: Barrel breakin

dbholster,

Sorry I have no pics of my barrel. I started this research back in 2001 - 2002ish time frame when I ruined the barrel. When Speedy inspected my barrel we view the bore scope on the TV since he had a video hookup to his bore scope. When Doug Shilen cut out the throat section, we didn't think to take pictures.

Next time I'm up to Speedy's shop I'll ask him if he has some pictures. Lord knows he had enough trashed barrels to look at.

BTW, my moly coated bullets were waxed, but I don't know if the wax played any roll in the destruction of my barrel?

Glad to hear you aren't having any issues.
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Mathew 5:16

Distance is not an issue, but the wind will make it interesting!
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