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CCI 300 or CCI 350 primers?

Discussion in '10mm Reloading Forum' started by Meathead9, Jun 18, 2010.

  1. Meathead9


    Aug 23, 2009
    The PRK
    Maybe I haven't looked in the right places, but the threads I have dug through are all over the place on the issue. Some say Mag primers are the only way to go. Others say to go with standard primers because they only lose 10-20 fps and keep pressures lower. Another thing I've read is that mag primers keep the ES tighter. I just bought my first press, and I will be using Longshot, 800-X, Blue Dot and some others down the road. I only plan on loading for 200gr/180gr/135gr for a while, so what's the current consensus?
    Last edited: Jun 18, 2010
  2. ctkelly


    May 9, 2010
    One consideration should be where do you live and the temperature you have....Iowa goes to both extremes and a mag primer is helpful when temps start dropping down to near zero.

    I've not had very much luck with 800x and obtaining good SD/ES numbers...using a 350 primer hasn't helped at all. I use a lyman digital powder dispenser that weighs each charge out to a tenth of a grain.

    AA #7 works great with 155-180 that i have tried so far. Power pistol is another good one, but I ignite that one with a winchester large pistol primer for practice rounds....showed good ES/SD.

    I would say go ahead and get the 350 primer.

  3. _The_Shadow

    _The_Shadow Ret. Fireman

    Jul 23, 2007
    Southeast, LoUiSiAna
    I use the CCI350 for heavy loads and the CCI300 for most target loads, but in some casings they are tough to seat the CCI primers(the cups are harder), I have found the Winchester LP primers easier to seat in most instances. Both have worked well.

    Using cases by one manufacture helps to keep the numbers tighter also.

    I see the numbers tighten up when powders occupy most of the case capacity balanced by bullets that help fill the space. Just the right balance and things seem to work better. Have seen some loads where adding more powder makes little or no changes in velocities...saturation I suppose.

    Just be careful and use good loading principles and practices. When I work near the upper limits I hand weigh each and every charge, even compare on two different scales.
  4. Taterhead

    Taterhead Counting Beans

    Dec 13, 2008
    Boise, Idaho
    I subscribe to the philosophy of using the smallest spark that works reliably. In my experience, 300s work great for almost all applications. It is the primer that I run BY FAR more than any other. With 300s, 800-X and Blue Dot work fine for me for everything up to max loads - no experience with Longshot. In my load work, 800-X and 350s exhibit pressure symptoms sooner than I'd expect. I've loaded as high as 14.5 grains of 800-X. The 300 primer has zero problems reliably igniting that charge. About the only powder I run with a 350 is A9.

    It is true that SDs and ESs are a bit tighter with the mag primer, but I'm not as concerned in a pistol cartridge about achieving the smallest standard deviations. Long range rifle is another story.

    If you have the time and components to burn, I'd do workups with both. You may find that the standard primer will work well for these powders with probably lower pressures. The 10mm auto is not nearly as large a case as some of those larger cases that call for mag primers.

    I've had situations where I've achieved higher max velocities with the standard primer because the mag primer loads exhibited pressure signs at lower charges relative to the standard primer.
  5. mejetski2000


    Jan 27, 2009
    Switching to mag primers cust my ES/SD with AA#7 and 150 Noslers in half. I live in Maine and I prefer the extra spark when temps plummet. I did the same with my Power Pistol load and it did reduce the variances but not as much as it did with AA#7.
  6. lethal tupperwa

    lethal tupperwa

    Aug 20, 2002
    Elmer Keith lived in a cold climate.

    He used regular Winchester primers

    for his .44 mags.
  7. chippy


    Jun 21, 2010
    FWIW - I have had the best results with Winchester WLP. I started using them by accident because they were all that was avail. at the time. I now prefer them over my previous "Favorite" brands. Especially with 10mm.
    Go Figure ?.....:upeyes: