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Substituting Magnum primers

Discussion in 'Handloading and Reloading' started by jim8115, Mar 26, 2013.

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  1. jim8115

    jim8115 Member

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    Since primers are so hard to get right now, I thought I would post these results;
    158 SWC , winchester primers
    HI / LOW AVG

    38 special 4.0 gr W231
    standard primer 772/731 754
    Magnum primer 783/739 763

    357 Magnum 6.8 Gr Unique
    Standard primer 1169/1111 1143
    Magnum primer 1169/1105 1147

    While I am not advocating substituting Magnum primers across the board, it appears that if you start low, work up and check your loads, you can safely use magnum primers in at least some applications.

    JIM
     
  2. RAH_66

    RAH_66 Member

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    From what I've read about the difference between standard and magnum primers is that the magnums burn hotter and longer to help the ignition of heavy magnum loads with slow burning powders. I've used both in 44 mag loads in the past and I never noticed a difference in how they felt but I didn't use a chrono on them. The chrono results I've seen on other sights comparing the two shows the magnum primers had a slight increase in pressure and a smaller std deviation.
    and came with the smart recommendation to start low and work up with the use of magnum primers with your loads.
     
  3. Clark

    Clark Member

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    At the threshold of brass yeild, magnum pistol primers are like .7 extra grain in pressure, but less in velocity.
     
  4. 4895

    4895 Member

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    It would be interesting to find out the velocity numbers using small rifle primers as well. Compared to small pistol magnum, I bet they are pretty close.
     
  5. jim8115

    jim8115 Member

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    Im not sure I understand. Can you explain?
     
  6. Walkalong

    Walkalong Moderator

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    Clark likes to push loads until it breaks something.

    What it means, is you need to figure the max load will be a little less with a mag primer. How much less? Depends on the powder speed etc, etc.

    .7 at the threshold brass yield is not where you want to be. :)
     
  7. jim8115

    jim8115 Member

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    So, what is threshold brass yield? And explain where .7 comes from. It just appears to me, that at the levels I am at, there is almost no difference in velocity. All other things being equal ( powder, case, bullet , etc ) pressure should equal velocity...
     
  8. Arkansas Paul

    Arkansas Paul Member

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    Thanks for posting that.
    I've always suspected that there was little difference. When magnum primers are all I can find, I do back off a little to be safe though. It's nice to see the real world comparison.
     
  9. Walkalong

    Walkalong Moderator

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    You'll need to ask Clark, but it is way over where you will be loading if you stick with tested load data. :)
     
  10. Clark

    Clark Member

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    CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.
    ~13 years ago, when I started handloading, I worked up AA#5 115 gr JHP to the point of the case bulge with case support at .19" and the case web is .16" thick, leaving .03" of thin unsupported case wall.
    This is a common case support for 9mm pistols like Kel-Tec and Glock.
    I backed off the charge, used small pistol magnum primers, and worked back up.
    It took .7 gr less powder to reach the threshold than with standard small primers.
    I could only get case bulges with 115, 124, or 147 gr bullets with AA#5, 3N37, and HS-6 powders.
    There was not enough room in the case for my other powder with lower speed- density products; Bullseye, Unique, Power Pistol, Blue Dot, 800X, AA#9, H110, nor LIL'GUN.
    This was only ~ 60% more powder than max book load, AA#5 is some miserable peaky stuff.

    That is only one powder in one application to equate magnum primer with powder increase, but it is the only datum we have:)
     
  11. jim8115

    jim8115 Member

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    Ok, so in your opinion, what effect will swapping to mag primers have on a 40S&W 180 Gr truncated cone @ 1.085 with 5.0 Grains of power pistol? Currently 900 FPS
     
  12. Clark

    Clark Member

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    Seat of the pants, it will act like 5.7 gr of powder with respect to pressure, but probably more like 5.2 gr of powder with respect to velocity.
     
  13. ArchAngelCD

    ArchAngelCD Member

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    Jim,
    Do you have the ES and SD numbers from your Chrono results? Those 2 numbers will tell you more when using standard and magnum primers than the velocity numbers will.
     
  14. Walkalong

    Walkalong Moderator

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    I agree with the velocity part, but have doubts about the pressure part. Any real test data?
     
  15. 32_d3gr33s

    32_d3gr33s Member

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    I guess I'm a little confused in this as well. I've done quite a bit of reading about people using magnum primers in 9mm rounds. Most of what I read says there is little to no difference between a standard primer and magnum other than slightly thicker metal on the primer cup, and the way it ignites a little more consistent.

    Here's where I'm confused.... The rule of thumb I've been reading is to reduce load by 10% and then work your way back up. I'm using green dot powder in my 9mm with 4.7 as max load. Suggested starting load is 4.2. If i reduce 10%, im at 4.2. So are you suggesting starting at 4.0 instead of 4.2? Or that because its .7 difference, that my 4.2 load with a magnum primer will be equal to a 4.9 load (pressure wise) as with a standard primer?
     
  16. Maj Dad

    Maj Dad Member

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    I'm with Walkalong on this. Unless you have some type of pressure testing guages (strain, crusher, etc.), all you can do is infer based on observations. Granted, a flattened primer that falls out of the case is a pretty good indicator of excessive pressure, but trying to equate smaller pressure differences to observable indicators is less precise, and may be the opposite of what we infer. Ken Watters used his case head measurements for years and had decent results, but later pressure testing showed it is imprecise. My first observed indicator was having to beat the bolt open on a nice 308 barreled VZ-24 in which I had fired max loads in military brass - lesson learned, never repeated. More subtle differences are not as pronounced (by definition), and require more than velocity to imply pressure differences.

    Having said all that, we have to use what is available, so in general, velocity can be useful to categorize loads, but there is no substitute for established loading data from reputable technical sources, and following established loading procedures, all of them.
     
  17. Maj Dad

    Maj Dad Member

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    32_d3gr33s, regarding your question about Green Dot, personally, I would just use the starting load of 4.2 for mag primers and work up from there. I think you'll find that there isn't much difference in results.
     
  18. Clark

    Clark Member

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    Case bulges are like blowing bubbles in brass.
    A thin piece of brass over a small hole has more pressure on one side than the other.
    When the difference in pressure is big enough, we get a bubble.
    Practice with bubble gum while watching yourself in a mirror until you get a feel for the concept.
     
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