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Thread: Overpressure with magnum primers?

  1. #1
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    Default Overpressure with magnum primers?

    Ok, Iíve tried to finish this post 3 times now and each time I do something stupid and lose the entire thing! Grrrrr. So, now Iím writing it in Word and save as I go so I wonít lose all my hard work again.

    Thanks to Vince, Iím ready to start loading some test rounds for my 300 win mag. (Vince, I hope you got some rest after arriving home) Iíve spent a fair amount of time looking up loads and all that other fun stuff and now I find myself at an impasse. I might be putting too much thought into this but right now, nearly everything I know about reloading Iíve learned in the last few months so Iím still a little tentative.

    Here is the starting load Iíve come up with using the manuals and online data.

    IMR 7828 75.0 gr
    Remington 150 gr SP bullet
    WLR primer - ďuh ohĒ I have CCI 250ís

    I found load recipes for 7828 and 150 grain bullets in my Lyman, Hodgdon, and IMR data and they all reference the WLR primer and NOT a magnum primer and thatís where Iím having a problem. Heck, even the guy at Boondocks whoís opinion I respect told me I was supposed to be using a magnum primer and he didnít have an answer when I asked why none of the manuals list data for them. Yes, as Vince told me already, I can load it using a Magnum primer and it will work and many, many people have done it. However, what kind of pressures am I going to be seeing? The Lyman manual uses WLR primers for itís data and merely states that higher pressure will result when using a magnum primer.

    Vince, I think you mentioned a recipe you use when you stopped by my store but I was trying to keep track of what was happening there and talk to you and now Iíve forgotten it.

    I have found articles that tell me a magnum primer in this case is required for slower burning powders which include 7828 and Iíve also seen recommendations that tell me I should reduce the starting powder charge by 4% - 5% and work up from there. One article even mentioned that pressures can go up by 20% over listed WLR data when using magnum primers!

    My gut tells me to start with 75 gr of the 7828 and work up in small increments to 76 or 77 gr while looking for signs of overpressure. I just hope I can spot them since Iíve never seen it before, other than a couple of pictures online. I have some fired rounds and I think Iíll use them as a sort of benchmark to compare to.

    Am I over-analyzing?

  2. #2
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    As you pull the trigger, just remember there is a potential hand grenade going off only inches from your face!!

    BOOOOOMMMM!!!

    Naawww, just use a good starting load and start shooting your groups across your chronograph. When you find a good one, load the rest of your brass. The "overpressure" thing is left over from the days of crappy brass; when you see the signs, you're already in the dead zone. Just use a load that gives you good groups. I use WLRM primers with everything, because that's what I have. Never had any probs with them.

    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

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    Quote Originally Posted by Bookseller View Post
    Am I over-analyzing?
    Yes, but there is no harm in being careful. 7828 is a slow powder for 150 grainers and that is why you are having a hard time finding data, my Speer manual has none for that combination. Speer starts to use it with 168 grain bullets and there they list 76 to 80 grains, using CCI 250 Mag primers. All loads they list with 7828 are compressed so it is on the slow side for the 300 WM even with heavier bullets. A load of 75 grains with CCI 250 primers should be more then safe behind a 150 grain bullet, though you will never get max posible velocity with this powder and bullet, it is just to slow. You will likely get more muzzle blast and flash with this load since there will likely be alot of unburned powder at the muzzle.

    Here are some pictures that may or may not help you with pressure signs. Yes I know that the rifle these where fired from has a firing pin that does not hit the center as it should.

    The first picture should show 3 cartridges fired in a commercial Mauser 98. The one on the left was a low pressure cast bullet start load @ about 20,000 CUP. Note that the primer is still radiused on the outside and the firing pin indent in also radiused. These are signs of low pressure. The middle cartridge was a start load with a jacketed bullet. Note there is a slight cratering of the primer at the firing pin, this is not a sign of pressure but a rifle fault. It is not very clear in the picture but there is also there is a slight ejector mark under the 30. In this case this is another rifle fault due to the bolt being slightly concave (yes this rifle has issues). The primer around the firing pin still shows a radius as does the outside of the primer. This is a sign of okay pressures. The right most cartridge is a max load, and shows signs of high pressure I will not fire this load again. Note, that the primer is not only no longer radiused on the outside but has flowed into the radius of the primer pocket of the case. Also note, that the primer has formed a sharp edge around the firing pin. There is also a noticeable ejector mark under the "ES" in Winchester. All of these point to high pressure, and that it is time to stop or back off.

    The second picture shows 2 primers taken from brass loaded the same as the left and right most in the first picture, and arranged the same. Note, the straight sides on the low pressure primer and large radius at the back. By comparison the High pressure primer shows the sides force out near the back forming a bit of a top hat shape. The radius where the sides meet the base is also noticeably sharper. This shows a high pressure load and it is time to back off. In general you do not want to see the top hat shape in a primer.

    Even with the high pressure loads shown here the primers did not fall out on bolt opening, bolt lift was normal, and the primer pocket still grips a new primer well. But failing to stop at this point leads to very short (one firing) brass life, hard bolt lift, and scary pressures, so it is best to stop or back off when the signs are seen.

    Just look at each case as you extract it and keep an eye out for signs like the right most case head, and if you see them do not increase the load. I fully expect your load to show signs like the left most cartridge in the first picture. Nice low pressures. So load a few up and go have fun.
    Attached Thumbnails Attached Thumbnails 100_1775.jpg   100_1779.jpg  

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    Thanks Nitro and Band. I'm done with all my around the house type stuff, the wife is fixing me a Father's Day dinner so it's time to go play. I'm going to load three progressively hotter loads and see how they work at the range. If I find one that works for me I'll come back and load the rest.

    Meanwhile I'll keep looking for H4350 for future loads.

    And thanks lot for posting the pics, they help a lot.

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    Your welcome. I thought I'd tease you a little about your post.

    You should go to Title Wave books and pick up some previously owned reloading manuals. Also, buy "Any Shot You Want" by Alphin.

    You can also find material at www.abe.com, and all powder manufacturers have their own websites with reloading data available. You can even call Accurate powder company and speak to a ballistician too, if it is about their powders.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

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    Quote Originally Posted by Nitroman View Post
    You should go to Title Wave books and pick up some previously owned reloading manuals. Also, buy "Any Shot You Want" by Alphin.
    What's this, more teasing? I'm actually ordering some for my store if they ever get back in stock but we'll see.

    Title wave, he he he

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    Nooooo....just offering a possible alternative to cruising garage sales. I don't want to incite and professional conflicts.

    I think you'd like Alphin's book. I bought one back in '96 when they first came out. Geared towards the experienced reloader, it is still a literal well of information for any reloader of any experience level.
    Great spirits have always found violent opposition from mediocre minds. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices but honestly and courageously uses his intelligence. Albert Einstein

    Better living through chemistry (I'm a chemist)

    You can piddle with the puppies, or run with the wolves...

  8. #8
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    Na i didn' give you any recipies... jut how i got my firsts done up... using the NOSLER Book with Nosler bullets. CZ started me out on the low end and built up 1/2 grain to the max loads... still have 8 rnds to shoot from that loading to find the correct ones... i shoot 180 grains for eve things so it is a good combo for me


    but of the 4 books i have been reading they all have MAG primers for the the 300.. get a Hornaday book... i think that is the one that explained them the best.... I still need to buy one for me yet.. CZ loaned me his... other wise i would loan it to you...


    but you know......


    you own a book store....


    that stuff should NOT be hard to look up...............
    "If you are on a continuous search to be offended, you will always find what you are looking for; even when it isn't there."

    meet on face book here

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    Quote Originally Posted by Vince View Post
    but of the 4 books i have been reading they all have MAG primers for the the 300.. get a Hornaday book... i think that is the one that explained them the best.... I still need to buy one for me yet.. CZ loaned me his... other wise i would loan it to you...


    but you know......


    you own a book store....


    that stuff should NOT be hard to look up...............
    LOL, ya but both of my distributors either do not carry those books or they are out of stock, (go figure). Speer won't sell to me since I'm not a sporting store and anyhow, my first order with them has to be prohibitively huge. I guess I'll just have to break down and spend the bucks myself, sigh.

    If I can get away for a couple of hours tomorrow I'm going to head out to the Birchwood range and fire off the loads I finished the other day. If I post again tomorrow night it means I musta done something right.

  10. #10
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    How old is your loading book? I have some Winchester WLR primers from about 20 years ago and the box says "For Standard or Magnum Loads". And I have used them for both a 30-06 and .300 Win mag loads with complete suscess. Still have about 300 of them and they work great but can't seem to find them anymore. Don't know if they changed the primer compound or not. But I recommend you use what the book says or start about 5% lower and work up.

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