#11
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Daryl, I'm pretty sure I understand how this works only been in business for 40+ yrs. including as owner of two cutter grinder shops. Heres where everyone gets confused I just had to explain to a customer last week. Customer calls he's a b.r. shooter says shooting "x" bullets from my dies .045 freebore and doesn't have much bullet in neck. Alright .045 with this particular nose radius is commonly used. I ask what his trim length is says 1.490 on 6 ppc which is pretty much run of the mill length, I ask what chamber length is 1.525. well theres the issue you come up with .045 +.035 +.015 = .095 instead. so he asks about "0" freebore tell him its not really the issue but chamber length is. Which is a Ptg reamer told him to send to me I will grind back to 1.500 length and change throat angle and all will work fine..So you need to include the 45* chamfer at end off chamber length to get true freebore number. And no matter what is said there is no real "0" freebore just not possible as I said before I don't care how good you dress wheels as soon as you touch off they wear so around .010 is about as good as it gets.
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#12
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Well we have about 10 different answers so far. Let me add my understanding.
If you get a reamer print from PT&G the leade will be the freebore you asked for. Some think and not wrong but different from the print, that freebore includes the safety factor "distance from the end of your brass to the start of the 45 degree transition" usually 0.010 minimum sometimes much more. The transition is 0.0137, so you have a minimum of 23.7 thousands that don't show on the print as freebore. You might have a little loss at the throat also. It's impossible to get zero freebore. It's possible to get zero leade. Clear as mud Eh. Kenny
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sicero I pride myself in being able to make decisions with little information. |
#13
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freebore and leade are all the same just different words...and the throat is angle coming from groove diameter to bore diameter..just to add some mud
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#14
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Following link from PT&G glossary.
http://www.pacifictoolandgauge.com/glossary.htm#f
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John |
#15
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John, Thanks for the link, pretty well sums it up, I do have an issue with what is said where increasing free bore allows more powder and you will get an increase in velocity. This is not really or should is say always the case and is usually not the case, when you move bullet out further ie increase freebore with out jamming bullet you also have less bullet in case so less neck tension so lower velocity. I might add that added freebore also works as a pressure release longer throat more of a pressure drop...But what do I know just working with military on dies and lab testing...
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#16
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It doesn't matter what's on the print PTG will screw it up anyway.
Adam |
#17
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amen to that, got a whole box from Dave that were lets say incorrect
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#18
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Quote:
Mr. Bentley, you are responsible for the large quantity of coffee now draining out of my sinuses! |
#19
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and now you are for me
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#20
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Sorry, George.
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