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-   -   Are my barrels shot out? (http://www.firearmstalk.com/forums/f33/my-barrels-shot-out-92805/)

Otley 06-24-2013 02:19 PM

Are my barrels shot out?
 
3 Attachment(s)
Hi there
I have owned a pair of Sako rifles since the 1980s and have not kept count of the number of rounds I have shot through them. I just made a Cerrosafe cast of the chambers and throats of each and was wondering if the experts here could take a look and tell me if the throats are badly eroded, or if there is still some life left.

Can you estimate the shot count that would produce these kinds of erosion? I assume that when the barrels were new, the rifling would have started very close to the case mouth part of the chamber.

The first photo is of the .223 Vixen; the last two are of the .308 Forester.

Thanks

danf_fl 06-24-2013 02:39 PM

Welcome to the Forum. When you sign in next time, stop by our "Introductions" area and say "Hi".

Are you having problems with accuracy?

IMO, The castings don't seem too bad.

c3shooter 06-24-2013 03:40 PM

Castings do not look bad, but to tell, you need a throat guage, have not had my eyeballs calibrated this month. Accuracy still OK? Good to go.

Distance bullet travels before rifling is the leade. There is good reason it does not start at the case neck- chambering a bullet would drive it into the rifling. Extract an unfired cartridge and the bullet would pull out of the case and stay in the bore. Some room there allows for different size and shape bullets. MATCH chambers less so.

Otley 07-15-2013 12:51 PM

Thanks for the replies.

I found the SAAMI chamber drawings and these show .07" of plain .224" bore from the case mouth to the commencement of the rifling for .223 and .09" of plain .310" bore from the case mouth to the commencement of the rifling for .308. So mine seem to be showing quite some lead erosion, unless Sako purposely cuts chambers with some free bore. It would be nice to find some scientific data that compares throat erosion vs number of shots vs accuracy for typical c/f cartridges.

JonM 07-15-2013 01:41 PM

If your concerned you need a throat erosion gage. A casting isnt going to tell you the info your after.

An ar15 can go about 25000 to 30000 rounds before the barrel can be considered shot out. Those rifles tend to lead a much harder life than most bolt guns.

Some chamberings like a 338 300mag and other large calibers wear faster than other rounds. A good way to judge is how much of a charge weight your burning at one time. The more powder in a bottleneck cartridge increases wear.

An erosion gage is the only way to tell the rate at which your using ip barrel life

gr8oldguy 07-15-2013 02:15 PM

the slugs seem to be showing good, sharp edges on the lands and groves. Could there be something else loose on the guns that are causing problems?

Sandycrack 07-17-2013 06:12 PM

Throat gauge is the best way to accurately answer your question. A bore scope can reveal a lot of information too. Throat erosion will begin with very small cracks and progress as you shoot more and a casting will not reveal them. If accuracy is down, a bore scope is handy to look for fouling and other problems. Be sure to look at the crown as any nicks can cause fliers.

hiwall 07-17-2013 10:52 PM

So has your accuracy dropped alot? Or are you just wondering? If they are still accurate then the barrel condition is meaningless. If you can achieve close to MOA(with some testing to find the best load) then be happy.

Otley 07-18-2013 03:26 PM

I suppose I'm just wondering really. I had this idea that the accurate life of a typical 50000 - 60000psi chamber pressure, jacketed bullet rifle was about 1000 rounds and I estimated that both of my Sakos were about there or more. The next new rifle I buy, I'll Cerrosafe cast the chamber when it's new, so I can monitor the wear. The .308 is as accurate as it has always been, but maybe the .223 is falling off a bit. Or it could be that I recently switched to military cases (though still with my standard 52gn Sierra Matchking bullets) and this has had an effect.

Of interest, I came across what I thought was a good idea for checking barrel wear on an Aussie video, which was to simply insert a cartridge bullet-first into the muzzle. If the bore is good, the bullet will only enter about 2/3rds of its length; if the barrel is worn, the bullet will enter the muzzle up to the case mouth. This being based on the principle that barrels wear both from the throat and the muzzle.

davemccarthy707 07-23-2013 03:11 AM

Looks good to me! Finnish steel is awesome ! ;)


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