Regular vs. magnum rifle primers

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  • boisepaw

    boisepaw
    Jan 5, 2015
    380
    Eastern shore, MD
    If I can't find regular Federal large rifle primers, is there any downside to using the magnum primers? What might be the problem with doing that?
     

    boisepaw

    boisepaw
    Jan 5, 2015
    380
    Eastern shore, MD
    The immediate question is loading for 6mm Creedmoor 105-107 grain bullets with H4350. And loading for 6.5 Creedmoor with 140 grain bullets with H4350. And loading 308...bullets anywhere from 168 to 175 to 185 to 205 grains. With H4895 or IMR 4895 or Varget or any number of other powders...
     

    Harrys

    Short Round
    Jul 12, 2014
    3,361
    SOMD
    If I can't find regular Federal large rifle primers, is there any downside to using the magnum primers? What might be the problem with doing that?

    A magnum primer ensures that slower burning powder (widely used in magnum loads) will burn more efficiently. There is a measurement called "brisance" which is basically how much fire comes out of the primer...more for magnum to set the slower powder to burn better.

    Secondary is the harder or tougher primer cup to allow a bit higher pressure before blowing a primer which adds about 3 to 5 more grains to your load. So if you use a 30 grain load for example you need to subtract 3-5 grains from your load. I use to have a chart chart that laid out the brisance and psi ratings for small and large pistol and rifle by manufacturers. I will see if I can find it.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    You can use them but should start load development over to be on the safe side.
    The only time this is really necessary is if you're already running on the hot side (eg, close to max). If you're running the more tepid loads most reloaders favor, it's unlikely that magnum primers are going to make much of a difference at all.
     

    Doco Overboard

    Ultimate Member
    You can use them but should start load development over to be on the safe side.

    Good advice-especially when you consider powder over or powder under combinations and changing environmental conditions like temperature.
    If you use reloaded ammo in more than one of the same rifle type magnum primers may preclude the use of the ammo one specific rifle only.
    Could be a downside.
     

    Blacksmith101

    Grumpy Old Man
    Jun 22, 2012
    22,154
    A magnum primer ensures that slower burning powder (widely used in magnum loads) will burn more efficiently. There is a measurement called "brisance" which is basically how much fire comes out of the primer...more for magnum to set the slower powder to burn better.

    Secondary is the harder or tougher primer cup to allow a bit higher pressure before blowing a primer which adds about 3 to 5 more grains to your load. So if you use a 30 grain load for example you need to subtract 3-5 grains from your load. I use to have a chart chart that laid out the brisance and psi ratings for small and large pistol and rifle by manufacturers. I will see if I can find it.

    I hope you find it, scan it and post it.

    Additional reloading information is always welcome.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    The only time this is really necessary is if you're already running on the hot side (eg, close to max). If you're running the more tepid loads most reloaders favor, it's unlikely that magnum primers are going to make much of a difference at all.

    But that also means it could.

    There was an article online, IIRC from Shooting Times, that did pressure testing on exactly the same load, with just different brands of primers and both Standard and Magnum.

    For lowest to highest pressure, but just changing primers, was something neat 15,000 psi.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    But that also means it could.

    There was an article online, IIRC from Shooting Times, that did pressure testing on exactly the same load, with just different brands of primers and both Standard and Magnum.

    For lowest to highest pressure, but just changing primers, was something neat 15,000 psi.
    I don't believe it without a link. The only ST article I could find on the subject didn't say anything resembling any of this.

    Most people get a 50fps or so velocity boost from a magnum primer. There is no way that's 15k psi. Otherwise you'd have the entire USPSA community shooting 9mm major using SPMs. :)

    I'm not saying don't run a small test batch to check for pressure signs, but starting from scratch is an extreme reaction to a primer change.
     

    Doco Overboard

    Ultimate Member
    Say for instance someone is using near max loads developed for a firearm that is already at the design limits for controlling pressure. A small increase in pressure that stems from the use of a magnum primer could yield catastrophic results to the user or wreck and damage the firearm without taking the correct precautionary measures.
    I don't know anyone who is using a large rifle primers in a 9mm cartridge which is out of the realm of the op's initial question.
    He wants to know about substituting Large rifle for magnum primers.
     
    Many years ago a friend and I did an experiment. We loaded up several rounds of 38 special using both standard and magnum primers and several rounds of 308 the same way and ran them through a chrono. The rifle rounds loaded with magnum primers averaged 13 FPS faster with no over pressure signs. I cannot remember what powder we used but it was probably IMR3031 since it was less expensive and could be used in 223.

    the handgun rounds with magnum primers actually were a tiny bit slower than the standard primers. Those were loaded with red dot I believe. I have used large magnum pistol primers in .45ACP without issue..

    All loads were middle of the road as far as powder weight goes.
     

    erwos

    The Hebrew Hammer
    MDS Supporter
    Mar 25, 2009
    13,866
    Rockville, MD
    Say for instance someone is using near max loads developed for a firearm that is already at the design limits for controlling pressure. A small increase in pressure that stems from the use of a magnum primer could yield catastrophic results to the user or wreck and damage the firearm without taking the correct precautionary measures.
    It's almost certainly fine unless you're at or near max. Even then, you're probably fine given how conservative most loading manuals are. That was literally my first answer. Run a small test batch, verify, and then move on.

    I don't know anyone who is using a large rifle primers in a 9mm cartridge which is out of the realm of the op's initial question.
    You understand small magnum pistol primers are a thing, right? Ironically, my box of large pistol primers says explicitly "good for magnum or standard loads".
     

    Doco Overboard

    Ultimate Member
    You understand small magnum pistol primers are a thing, right? Ironically, my box of large pistol primers says explicitly "good for magnum or standard loads".

    Yes I understand completely, you must be describing this thing. You know it must be the well ahh you know the thing. C'mon You know what I mean. Im being intentionally facetious here on purpose.

    Capture SR-SP.PNG

    What the op wants to know is that if there could be negative repercussions from the substitution of LRP's with another type designated as Magnum.

    As far as publishers of loading data are concerned and what is generally accepted as a conservative load, what is very well known is that a reduction of a powder charge almost always results in less pressure and an increased margin of safety.
    The same safety measures are what will alert a conscious hand loader to notice the signs of excessive pressure before they become a problem or cause damage during load development.

    What generally or rarely does not get discussed in topics such as this is what could be considered the primary reason for what is considered a conservative load in published data.

    What publishers, ballisiticians and everyday hand loaders cannot or never will be able to accurately predict are the negative mechanical effects that can be associated with an arm that can be identified as contributors to excessive pressure.

    For instance, a firearm with a new barrel can exhibit higher than anticipated pressure initially, but once broken in may settle in to an expected level of performance.

    In contrast to the above, a firearm that has been very well used and has been in continual service for a specific length of time with ordinary acceptable performance, could be subject to an unanticipated pressure spike because of additional forces created by friction of the bullet such as when forcement occurs.
    And that's only one condition that could cause an unanticipated increase of pressure as well as a variable that cannot accurately be forecasted.

    When an individual assembles components one could easily miss or even intentionally overlook an important safety or performance aspect.

    I also read earlier where you recommended a reduction during charging to which I agree to some extent.
    I would always recommend starting over because you never really know what someone may be doing or what they may be working with.
     

    Pinecone

    Ultimate Member
    MDS Supporter
    Feb 4, 2013
    28,175
    I don't believe it without a link. The only ST article I could find on the subject didn't say anything resembling any of this.

    Most people get a 50fps or so velocity boost from a magnum primer. There is no way that's 15k psi. Otherwise you'd have the entire USPSA community shooting 9mm major using SPMs. :)

    I'm not saying don't run a small test batch to check for pressure signs, but starting from scratch is an extreme reaction to a primer change.

    As I said, the one I was talking about, I have not been able to find.

    But this from another thread:

    https://www.shootingtimes.com/editorial/ammunition_st_mamotaip_200909/100079

    We heard a number of requests to add a primer chart in the Speer manuals I wrote showing what the various primer makers call their primer types. Note that there are no such charts in my books. Why? First, switching primer brands from what we used in the manual could create an unsafe condition.

    Here we have a situation where lower pressures gave higher velocities.

    You could have higher pressure spikes, but lower average pressure, so not see major changes in velocity.

    We have a classic case study in the .22 Hornet. For years Speer used Small Rifle primers in the Hornet. When I shot some of the data for Speer Reloading Manual Number 12, I found too many propellants that were so rangy they would not meet my standards for publishable loads. As a result, we did not show very many propellants for the Hornet, and the velocities were rather modest.

    While I was developing the .22 Hornet 33-grain TNT HP bullet, I tried Small Pistol primers, knowing from the 9mm experience above that such a light bullet could be unseated by primer power alone. I'd talked to a number of handloaders who were getting better accuracy with Small Pistol primers, and I wanted a look at the concept in a lab setting. Sure enough, switching to Small Pistol primers reduced the variations in pressure and velocity and also reduced average pressure. The latter let us safely run the charge weights a little higher for velocities more appropriate to the Hornet. Manual Number 14 shows many more Hornet loads with better velocities, thanks to Small Pistol primers.
     

    Uncle Duke

    Ultimate Member
    MDS Supporter
    Feb 2, 2013
    11,662
    Not Far Enough from the City
    As I said, the one I was talking about, I have not been able to find.

    But this from another thread:

    https://www.shootingtimes.com/editorial/ammunition_st_mamotaip_200909/100079



    Here we have a situation where lower pressures gave higher velocities.

    You could have higher pressure spikes, but lower average pressure, so not see major changes in velocity.

    We have a classic case study in the .22 Hornet. For years Speer used Small Rifle primers in the Hornet. When I shot some of the data for Speer Reloading Manual Number 12, I found too many propellants that were so rangy they would not meet my standards for publishable loads. As a result, we did not show very many propellants for the Hornet, and the velocities were rather modest.

    While I was developing the .22 Hornet 33-grain TNT HP bullet, I tried Small Pistol primers, knowing from the 9mm experience above that such a light bullet could be unseated by primer power alone. I'd talked to a number of handloaders who were getting better accuracy with Small Pistol primers, and I wanted a look at the concept in a lab setting. Sure enough, switching to Small Pistol primers reduced the variations in pressure and velocity and also reduced average pressure. The latter let us safely run the charge weights a little higher for velocities more appropriate to the Hornet. Manual Number 14 shows many more Hornet loads with better velocities, thanks to Small Pistol primers.

    This perhaps? Goes back a ways.

    I remember this article in relation to what can prove to be BIG swings given component changes. And however otherwise helpful, a chronograph can't show them, any more than an X-ray measures heart rate.
    http://kwk.us/chronographs.html
     

    Harrys

    Short Round
    Jul 12, 2014
    3,361
    SOMD
    Primer Cross Reference

    Primer Crosences Refer
     

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