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sizing question

 
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  #1  
Old 02-15-2011, 08:46 PM
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sizing question

Ok, so I fired some rounds through my new gun. I will reload when I have probably fifty or so to load at a time. I have been very interested in reading about bumping the case shoulder to fit my gun's particular chamber. I thought I would give it a try and see if I could feel the "crush fit" that so many have talked about, however I failed. Is it possible that the virgin brass that I loaded and shot has not "grown" or stretched enough? I took the brass (now it is once fired), chambered it in my gun taking note of how the bolt closed. I felt no resistance increase when compared to an empty chamber. I then lubed and sized the brass with the Forster BR full-length sizing die backed out one full turn. Chambered the brass again, and as before, no increased bolt stiffness. I repeated this procedure turning the sizing die down about an 1/8th of a turn each time until the die was touching the shellholder in the end. At no point did I notice any increase in bolt stiffness. Have the cases not stretched enough? Or have I likely went past the point of crush fit with turning the die in such large increments? Just wondering if during an 1/8th inch turn I went from just barely sizing the neck to over-bumping the shoulder. I look forward to the input. Thanks guys.
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Old 02-16-2011, 07:24 AM
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Re: sizing question

depending on the load, it could take 2-4x firings to get the hard crush fit that you need to figure out where the shoulder is actually touching.

Simple way is to fire 2-3 pieces of brass 3 times or so and use them as your reference for shoulder and body sizing measurements.

From that crush fit point you want to bump it back .001-.002 where you just no longer feel the crush fit.

BH
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Old 02-16-2011, 09:49 AM
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Re: sizing question

So for my now once-fired brass shouldnt I just size the neck enough to basically seat the bullet and be done with it? No need to run through the sizer if it fits right?
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Old 02-18-2011, 11:24 AM
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Re: sizing question

CRNA,

Just a heads up here, but that 1/8th turn of the die equates to about .009" movement of the shoulder. Little bit of die adjustment goes a long, long way here. That .009" can go from a very tight crush fit, to an excessive headspace situation in just one stroke. Try 1/16th of a turn (or less), and go slowly here. Better yet, check into a set of bump gages so you can accurately see and measure what's going on in the die when you make such an adjustment.
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Old 02-18-2011, 12:46 PM
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Re: sizing question

Understand that there is normally only .006 between a GO and NO GO. Plus maybe another .009-.010 if they are spec'd all the way out for a FIELD gauge.

Got to go very small movements.

HINT Sinlcail international sells die shim packs for under $10 or the Redding competition shellholders.

Both of these make it possible to use one die for two different guns without changing the locked down position.

BH
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Old 02-18-2011, 09:34 PM
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Re: sizing question

Thanks guys. I am definitely going to invest in some equipment to measure this without going by the feel.
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Old 02-18-2011, 11:56 PM
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Re: sizing question

The RCBS Precision Mic will also help you in that department (if you have a factory cartridge). I've been using them in 223, 22-250, 220 Swift, 243, and 25-06 for about 17-18 years now. They cost about $50, and well worth the money IMO.

You might also try just neck sizing until the fired brass gets slightly tough to chamber......that's where the shoulder bump comes in. If the cases haven't stretched enough to fill the chamber yet, and you're bumping the shoulder and FL sizing already, it could cause problems like case head separation.

Not saying it will, just saying it could. I had that problem with my 220 Swift. That's when I found the Precision Mic and Neck sizing dies. Happily ever after.
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