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CDM vs Starline case capacity?

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Pantera Mike View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Pantera Mike Quote  Post ReplyReply Direct Link To This Post Topic: CDM vs Starline case capacity?
    Posted: 08 Aug 2018 at 8:31am
Does anybody know for sure how the capacity of Starline cases compares to that of CDM, Norma, and typical rifle brass?

I ask because period load data is all over the map, and it’s suggested that case capacity can vary considerably. The impression I get is that for a given amount of powder, pressures will be higher in cases with a smaller capacity, and loads need to be adjusted accordingly.

Grains of water seems to be the typical method of measuring case volume. Somewhere I remember reading a comparison between several different types of brass but for the life of me I can’t remember where it was.

If somebody had some Starline and CDM cases and could produce the comparative volumes of each (either using water or gunpowder, filling each case up to the brim and then measuring the weight of the measuring medium) that would be great!
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Benny123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Benny123 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 3:39pm
I recall the articles of Lee Jurras comparing different brass types for the 44AMP. I only have Starline. I would expect the rifle parent case with increased wall thickness to have the least capacity, and CDM, the greatest of the bunch . The impression that you got that pressure will be greater with smaller capacity is spelled out many years ago by the ideal gas law PV=nRT. ......volume decreases, pressure goes up


There are a lot of collectors of that old stuff around . Hopefully someone will chime in. If memory serves I felt like, Lee referenced CDM as having the greatest case capacity, albeit nominal
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jw4570 View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 10:20pm
Look no further than Ian's Site for an article by Barry Duckworth and Bruce Stark.

The case capacity is actually compared using grains of WW296, but I think it's the relative capacities you are looking for:

http://www.amtguns.net/articles/bruce-stark/in-search-of-1250-fps/

Jason
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CrazyLarry View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote CrazyLarry Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 10:50pm
From what I have seen measured:

(lowest to highest resized 308 brass capacities)
LC-NATO
WCC-NATO
Fed-GMM
Winchester
Remington

NATO brass is nearly all identical, but, there are lot-2-lot differences anyhow.

Cut down military brass has the thickest amount of metal around the bottom, therefore it "should" last longer.


Starline brass is made "thicker" than 44mag brass at the web/primer pocket, but, not by much.

If I were going for 1300fps with a 240gr bullet, an 8.5" barrel is needed.
From what I have read else where with 308 based loads, there is not that much of a difference in capacities for pistol rounds that end up with significant changes to velocity.


Now, in a rifle, that is a different story. I used to cut down 30-06 REM brass to make 300SAV before I scored a bag of once fired REM cases at a gun show. Cut down 30-06 was 100fps consistently slower than resized original 300SAV brass.
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Benny123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Benny123 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 11:04pm
That’s a really informative article by B Stark. And I forgot about it, when I first saw the title I really didn’t understand the need to search for a moderate load and how one could use a slow-burn pistol based powder for an otherwise slow moderate load. Charges of w296/h110, and mp300 are designed to be almost at capacity. And the part that states that no pressure testing has been done with respect to the cartridge. Didn’t Lee Jurras produce his own line of ammo , Supervel, and was the first to commisison a pressure gun for this cartridge, he’s stated in the articles around a 40- 45K max pressure range, with charge details for his own line of bullets and others. I dunno maybe I’m wrong. As Ive mentioned before anything Detailed oriented about the automag I learned from this Ian site and forum .
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jw4570 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 11:24pm
Lee Did Pressure test something like 6 loads of SuperVel.  I have the pages somewhere.  He had them up on his site when he had it.
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jw4570 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 11:34pm
I uploaded the files but can't figure how to link them here...

It says Error inserting it in current location

And I can't access the FAQ again.

Jason
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jw4570 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 11:39pm
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jw4570 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jw4570 Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 2018 at 11:45pm
I forgot one was with discontinued 630 powder.  296 and Blue dot still around.  3 44's and 3 357's pressure tested.

Maybe Ian can add this to his info page?
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Benny123 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Benny123 Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2018 at 12:00am
Nice job—all came through
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