Primers 101 - for those starting out on reloading.

This is a discussion on Primers 101 - for those starting out on reloading. within the Reloading forums, part of the Defensive Ammunition & Ballistics category; Anyone who has been reloading will of course be well aware of primers and their two basic types - this is to assist those who ...

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Thread: Primers 101 - for those starting out on reloading.

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    Primers 101 - for those starting out on reloading.

    Anyone who has been reloading will of course be well aware of primers and their two basic types - this is to assist those who are considering starting out and may not as yet have a full grasp on this subject. It is covering hopefully the main points of interest. Two types of primer exist and to this end I have generated a simplistic diagram to help explain.






    These days by far the most common are the "Boxer" primers - what we might call a 'self-contained'' primer unit. The cartridge case has a primer pocket into which the primer is inserted and has a central flash hole thru which an ignition flame passes to ignite the powder charge. It is this single central hole which enables depriming to be done so easily with a projecting pin - usually part of a reload press sizing die or even a dedicated depriming device.

    The primer cup is pressed out of a small metal blank and then a thin layer of priming compound is applied internally to the base - a chemical mix that is very stable within a large temperature range but which can be initiated by sudden energy input. To achieve this effect there has to be something against the primer compound to resist the input of energy from a firing pin to the outside of the primer cup - that is the anvil.

    With Boxer priming the anvil is integral and is essentially a three 'petal' very thin piece of metal which is formed such that it is concave, the center portion being positioned such that it is all but touching the priming compound. The 'petals' or''legs'' usually project slightly from the edge of the primer cup prior to installation but as the whole primer unit is seated, these legs come into contact with the base of the cartridge case primer pocket - pushing the anvil into greater contact with the compound. This is commonly regarded as ''sensitizing'' the primer.

    Finally ..... all that is needed is for a firing pin to indent the primer cup externally such that the compound is impacted aginst the anvil - with we hope a resulting production of very hot flame to initiate the powder charge.







    The "Berdan" primer is a very old design and well predates the Boxer type. In this case the formed primer cup is just containing a layer of priming compound but no anvil. The anvil is part of the cartridge case primer pocket - usually a simple central post, either side of which are commonly two small flash holes. Once the primer has been seated it will usually leave the anvil in contact with the priming compound and then when there is a firing pin strike, once more there is a resisting force against the compound and the impact initiates it.

    As there is no centre flash hole like the Boxer type, spent primer removal is much less easy. There are two ways in essence to achieve this - one is by use of hydraulic pressure from within the case - I have a device for doing this but it's messy. The other way is using a gadget from Lyman or RCBS which uses a hook/ lever principle to pierce the old primer and pull it out .... it works but not every time.

    For most practical purposes the Boxer type is the one most used - however if light is shone inside a cartridge case it is easy to see by flash hole orientation which type has been employed. It is probably most convenient to not bother with reloading Berdan cases unless, as I do - you want to reload something like old milsurp .303. If required I will post some info on the Berdan removal tools and methods. It might also be mentioned that Berdan primers are much harder to find now, altho I believe 'Old Western Scrounger" still stocks some.


    Primer ''hardness" ..........

    This is a frequently discussed matter and opinions do seem to vary somewhat. Overall however and from my own experience CCI primers are the hardest and so seem to require a harder hit to reliably go off. Winchesters seem softer and Federal softer yet and for this reason I have used Federal most of the time over many years. The differences can be most obvious putting rounds thru a revolver which has been tuned such that the pin strike is weaker - and then harder primers can be found to be unreliable. Most semi's however will or should manage all primers.


    Corrosive primers .......

    Modern priming compound is to all intents corrosion free, the most common over many years having been based on lead styphnate (which of course potentially can put a small quantity of lead into the air with use). We do now see other compounds coming into use which purport to be better regarding pollution - I am not well up on the newer chemistry.

    Go back further tho and in particular older mil surp stuff, which in fact may often be Berdan primed - we find priming compound based on chlorates. It works for sure but - downside is the residue left in the barrel. The important thing to remember is the corrosive products are hygroscopic (Suck water from atmosphere) and so with water become dilute mineral acid - cleaning therefore needs to be water based for stage one, much as you'd do after shooting black powder. Leave a bore too long and you may find rust coming quickly.


    Tubby has posted some useful info on primers, with regard to them being useful to show over pressure signs - this is well worth checking out. It is worth remembering that a spent primer firing pin indent is usually exaggerated in depth appearance, due to set-back of the primer on firing - it tries to exit the case but as the case impacts the breech face it is pushed back in but with the firing pin often not yet retracted and exaggerating the indent.
    Chris - P95
    NRA Certified Instructor & NRA Life Member.

    "To own a gun and assume that you are armed
    is like owning a piano and assuming that you are a musician!."


    http://www.rkba-2a.com/ - a portal for 2A links, articles and some videos.

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    VIP Member Array SatCong's Avatar
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    Very good! Should keep, this would help new reloaders! You did nice job.

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    VIP Member Array Bud White's Avatar
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    Federal Match are the Softest Primers

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    The diagrams are very clear. This is a nice presentation.

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    VIP Member Array raevan's Avatar
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    Just an added note in history.

    VII. Reloading Information
    F. Terminology
    3. Berdan vs. Boxer Primers
    by Michael Knape (video@plexusmi.com)

    So what is the difference between berdan and boxer primed ammo? Is either prefereable for .308 or 7.62 x 39 practice, storage, etc?
    Primers in the U.S. are often referred to as Boxer primers, after the designer, Edward M. Boxer, a British Army Officer during the mid 1800's. At about the same time, an American ordinance officer, Hiram Berdan, introduced a different priming system in the U.S. The Berdan primer uses 2 or 3 smaller flash holes that are off center and surround an anvil that is formed as part of the bottom of the primer pocket. From a manufacturing standpoint, Berdan's system is simpler and less expensive, but cases of this type are extremely difficult to reload. Aluminum CCI Blaser cartridges use this system and are not reloadable. Ironically, it was the British Boxer system that the U.S. has adopted, while the American Berdan system is still widely used in Great Britain, and Europe. The Boxer system uses a larger centered flash hole and the anvil is a separate metal piece that's held inside the primer cup.

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    Thanks for the extra - I confess I skipped most of the historic stuff due to laziness Always forget also how old the Boxer concept is but am glad we mostly use it nowadays.
    Chris - P95
    NRA Certified Instructor & NRA Life Member.

    "To own a gun and assume that you are armed
    is like owning a piano and assuming that you are a musician!."


    http://www.rkba-2a.com/ - a portal for 2A links, articles and some videos.

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    VIP Member Array friesepferd's Avatar
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    very nice. thanks for the info!

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