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Personally in my opinion it is not the bullet travelling over these marks outside of the first 1 or 3 shots where the actual soft bullet jacket may trap and collect any microscopic loose edges of these machining tool marks as they passes over the throat that smooths these marks but rather the blow torch effect of powder combustion and extreme temperature that eventually causes the firecracking that we are all familiar with that rounds off those copper stripping sharp edges. Just my current thoughts, subject to change and enlightenment.:) |
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Contrary to what you believe the leade and throat are part of the chamber and are the same on all Sammi Speced chambers. If they or the neck area are changed, as in the drawing 260 Rem posted, it is not a saami speced cartridge but a custom chamber. As the leade (freebore) is larger in diameter than the bullet diameter the bullet should not contact the chamber until it reaches the lands which are just past the conical throat. Of course there could be enough contact between the bullet and leade (freebore) to cause copper transfer if the bullet runout is excessive. Here is a link to a post with picture that may help : http://noebulletmolds.com/smf/index.php?topic=89.0 |
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Rough chambers are bad news , iclund is correct about a good smith and a sharp reamer will produce a good chamber . How ever we have tested chambers up to a 2500 grit finish (polished ) and had non of the issues claimed ,problem is most people will wreck a chamber polishing if there not careful ,it’s easy to make the chamber big at the back if you get aggressive , |
Thanks HW223 - new thread posted. Look forward to the info.
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Brass fired in good chamber that was specked 0.374" at the base datum measures just under 0.374": [IMG]http://i920.photobucket.com/albums/a...psec0124a7.jpg[/IMG] Brass fired in chamber that was polished out to 0.377" or 0.003" over spec. ahead of the base datum: [IMG]http://i920.photobucket.com/albums/a...psc5c40648.jpg[/IMG] Full Length sized to just under 0.373", at the base datum, showing area where the 0.004" bulge was created by polishing out the base of the chamber. [IMG]http://i920.photobucket.com/albums/a...ps38d77a8f.jpg[/IMG] |
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The BI procedure outlined by HW223 confirms my conviction that the process is of real value. Of particular interest is the use of a bore scope to determine exactly what is happening...especially during those first few shots...where failure to remove a copper deposit means that the underlying “issue” may not be addressed.
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If your looking in the barrel with a bore scope and have zero copper that is excellent , harder to achieve than people think , can’t tell by looking at patches. Like I said what we do in srb is not relevant to most , we are looking to agg in the mid to high ones ,need to eliminate all causes stray bullets
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That is what I have seen with every benchmark barrel I have ever chambered. The slightest amount of copper after the first 20 rounds. Give it a good clean and pretty much zero copper from then on out.
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HW223 - I think most shooters would benefit from emulating practices illustrated in the BR playbook whether it be BI routine, bag set-up, trigger control....etc. Don't think I ever ran into a shooter that wasn't interested in upping their game. When I started shooting at paper I thought 3 shot groups of 1.5" @100m were decent ...but when I saw others doing better, I started watching, asking questions and getting tips ...especially from the shooters that demonstrated they knew what they were doing by posting good groups.
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The internet is a big part of the problem , to many guys with all the answers that never Compete anywhere , like it or not how we find the best way is by competing against others who think they also have the best way, separates the bs from what really works pretty fast , that goes for any discipline Not everyone wants to get the most from the rifle sometimes minute of gopher is enough |
Excellent
Perfectly put, no insulting anyone, no put downs, just a fellow shooter with experience sharing his knowledge. This is what makes AO a good read, it’s to bad you have to wade through the garbage to get to it.
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Warren Page did an article about actual accuracy requirements and parameters in the late 60's IIRC. Cat |
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Find a class that it fits and compete , that’s the only way to find out
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But it won’t compete. Even if I break in the barrel.
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Good luck and good shooting with what ever you decide to do |
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I do not break in custom barrels anymore other than my shoot a bunch to get it going, clean it down to white patches (Wipeout is the favorite) and the get it dirty again and start load development. I have several very accurate and consistent rifles that behave this way after that treatment. I'm not an SBR shooter, but I did read about them once. :) |
To say that my barrel needs breaking in because guys shooting benchrest break their barrels in is disingenuous at best. My wife doesn’t need formula 1 racing tires on the car so she is more efficient at getting groceries. Let’s face it. There is more to winning a formula 1 race than the tires, and driving a formula 1 racing car in town, not only increases the cost of groceries, it makes it more difficult to carry your groceries home.
That’s why I posted a picture of that rifle. We have people telling the world here that they need formula 1 racing tires on their SUV. |
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