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Thread: Reloading for fluted chambers

  1. #1
    holescreek's Avatar
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    Reloading for fluted chambers

    I've been concentrating on reloading for my Cetme GHG1 for several months. I lucked up on a video series on Youtube by a fellow that posts as "Pan Handle Precision" and was relieved to find that much of what I was doing was correct while also picking up some good tips. Here's a link to Part 1 of 5: https://www.youtube.com/watch?v=R37Wk_voTOY

    Besides not keeping a log book, I discovered that I should have been measuring the shoulder height of the cases for reasons I will talk about later. A couple companies make attachments to fit on your digital calipers to measure with but I never buy what I can make. The measurements are strictly "comparative" meaning that two different gauge setups (calipers with attachments on them) will not match readings directly so everything you measure must be done with the same caliper and attachment.

    Here's the attachment I made:

    20190110_120921.jpg

    I measured a lot of new Lake City brass and got an average of 1.520" on the shoulder.

    20190110_120853.jpg

    The piece of brass shown next has already been fired 4 times, I cleaned the soot off of it for the photo so you can see the raised flute marks. The shoulder measurement over the flute marks on this case was 1.529".

    20190110_120512.jpg

    20190110_120554.jpg

    When I started paying attention I discovered that after sizing, the flutes on the cartridge shoulder weren't getting compressed back down into the shoulder. The problem here is that the flutes on a reloaded cartridge weren't likely to be aligned with the chamber flutes on subsequent firings. After some head scratching I discovered that my LEE sizing die was too long and ground the base down so that it compressed the cartridge shoulder to the correct height.

    20190110_120733.jpg

    The shiny areas on the shoulder are a direct result of contact with the repaired sizing die:

    20190110_120824.jpg

    20190110_120140.jpg
    Last edited by holescreek; 01-10-2019 at 01:48 PM.

  2. #2
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    Nice job on the adaptor. They still won't let me use a lathe at work, not even on my own time lol! I'll have one in my shed when I get to my retirement digs. I use a Hornady comparator.
    How far back are you setting your shoulders? I'm bumping back .003" for the M14 and M1, and they are dropping in the Hornady case gage just fine. What dies are you using?
    I went with RCBS small base X dies as they're supposed to greatly increase case life. The last batch of that S. Korean milsurp brass I loaded is on it's 4th loading and I saw no signs of imminent base separation. Those fluted chambers look very hard on brass.
    Last edited by Don in IA; 01-10-2019 at 05:13 PM.

  3. #3
    holescreek's Avatar
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    Before I paid attention to the shoulders they were becoming very ribbed and added even more ribs with each reloading cycle. Of course the Lee sizing die wasn't touching them so they kept piling up. Now that the die is repaired I'm setting the shoulders back .003~.005", it's hard to get it just right when the brass extrusion into the flutes can be different from case to case based on brass hardness.

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