July 12, 2009, 12:54 PM | #1 |
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Join Date: September 18, 2008
Location: Marquette,Mi
Posts: 89
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Semi Auto Headspace
I am getting case head separation on my second and third firings out of an Armalite AR-10T. Is this normal for an semi auto or should i be able to get more firings out of an 308.
1)I screw my full length sizer die till it touches the shell holder and run my once fired cases through 2)then trim and tumble and what not drop in some varget (43 grains) place a 168 grain sierra on top seat till 2.80 and shoot the day lights out of steel and paper. Is something wrong with how I reload? |
July 12, 2009, 01:07 PM | #2 |
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Join Date: June 14, 2007
Posts: 115
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I think there could be two possibilities going on with headspace, the first more likely than the second:
1) your rifle's headspace could be out of spec (too long) which stretches the cases excessively, leading to the case head separations you're seeing 2) your resizing dies might not be manufactured to spec, resulting in an out of spec cartridge headspace. I have read that die manufacturer's use a reamer to cut out the inside of the sizer die and that as the reamer wears, the size of the inside of the die can vary some. I would suggest checking the rifle's headspace, and running your resized cases through a cartridge headspace gauge. By "checking the rifle's headspace" I mean do it yourself or take it to a gunsmith to do it. My local guy charges about $40 to do it, and IIRC a set of rifle go and no-go gauges would be about $50 or so, so I bring the guns to him rather than buy the gauges. As far as cartridge headspace gauges, I've been trying to buy some for awhile. I don't have any case separation issues but I don't have any measurable proof that my dies are resizing the cases totally proper. Another good reason to get cartridge headspace gauges is because some brass is "springier" than others, so even though you followed your dies' instructions exactly, the case shoulder "springs back" after you size it, resulting in an out of spec case. |
July 12, 2009, 04:18 PM | #3 |
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Join Date: September 8, 2004
Location: Kansas
Posts: 723
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I bet your resizing your brass to much. You probably don't need to screw your sizing die down that much. Buy one of these and measure a fired case.
http://www.sinclairintl.com/product/...eadspace-Tools I don’t have a 308 semi-auto but in my 223’s I resize the case .002 or .003 smaller than a fired case. Works great!!
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