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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
    Senior Veteran Don in IA's Avatar
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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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    Ribs on your cases mean the flutes are either not quite right or they are dirty and full of crap. If they are flowing gas properly the brass won't flow into them. This is one of the main problems green mountain had with their fluting on the HK 33 barrels they made. HMG had issues with some of their barrels as well. They would shoot steel fine but brass flowed into the flutes blocking off gas flow and the cases tend to stick. In their barrels the biggest problem was that the flutes weren't carried down the shoulder as deep as the neck so the gas would get choked off and not flow to the body where it was most needed.
    In my Swiss rifles, the SIG Stgw / PE 57 and the AMT the brass never flows into the flutes so you don't need to worry about sizing the raised brass to get it flush again. The same goes for some factory HK rifles. I have seen issues when the flutes get filled with carbon and crap but a good clean and it usually straightens out again. That makes it much easier to resize the cases as you only need to push the shoulder back to insure proper headspace length....which in the roller lockers isn't as important unless it keeps the bolt from going forward enough to set the rollers properly. I've had really good results loading for the PE 57 with Privi partizan brass loaded 7 or 8 times so far with no necks splitting or other problems.

    Just my 2 cents.

    Frank

  5. #5
    Senior Veteran Windy's Avatar
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    I am curious as to how many reloadings you guys are getting on a case??
    Luv me some cosmoline!

    Ears to the ground, nose to wind and my hackles are rising.

    “If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen.” -Samuel Adams

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    holescreek's Avatar
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    I tried to keep track but got bored with it and stopped counting after 12 reloads. I trim my cases as needed but have never annealed one. All my case "failures" have been due to expansion down at the rim where the die doesn't contact the brass. When the brass won't slide into the shoe of the press any more I toss it out.

  7. #7
    Senior Veteran Windy's Avatar
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    that's honestly more than I thought. Comparing your brass to mine, yours seems in a lot better shape. LOL, mine looks like a chamber casting...
    Luv me some cosmoline!

    Ears to the ground, nose to wind and my hackles are rising.

    “If ye love wealth better than liberty, the tranquility of servitude better than the animating contest of freedom, go home from us in peace. We ask not your counsels or arms. Crouch down and lick the hands which feed you. May your chains set lightly upon you, and may posterity forget that ye were our countrymen.” -Samuel Adams

  8. #8
    Senior Veteran Don in IA's Avatar
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    Quote Originally Posted by holescreek View Post
    I tried to keep track but got bored with it and stopped counting after 12 reloads. I trim my cases as needed but have never annealed one. All my case "failures" have been due to expansion down at the rim where the die doesn't contact the brass. When the brass won't slide into the shoe of the press any more I toss it out.
    I had some cases out of my M14 that wouldn't drop in the case gage after sizing. Noticed the extractor was being "aggressive" leaving a slight burr on the rim. Sticking those rim first in the gage fixed most of them. Being cheap, a quick swipe with a hone stone fixed the rest. I try hard to get it to last until the primer pockets get loose lol!

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