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Question about using small pistol magnum primers in a .40

Discussion in 'Reloading' started by imknadian, Apr 4, 2010.

  1. imknadian


    Jun 7, 2007
    I bought some primers at Scheels yesterday for my .40 cal. When I got home, I realized they were small pistol magnum primers instead of the regular small pistol primers that I usually use.

    Is it possible to load safely using the small pistol magnum primers? Are there any issues? Currently I am using 4.8grains of tightgroup and getting around 1050fps with 180grs using the regular primers.
  2. wavetrain75

    wavetrain75 Useless Member

    Jan 31, 2008
    I was told by the guy behind the gun counter (and we all know they're never wrong) to dial back your load by 1/10 grain when using magnum primers, and to stay at least 2/10 or 3/10 grain below maximum charge.

  3. ron59

    ron59 Bustin Caps

    Jan 3, 2009
    Smyrna, GA
    I run sp magnum primers with my 9mm loads... no problem. It only makes a difference of a few fps (8, 10 maybe?) across the chrono.

    DEADLYACCURATE Senior Member

    Oct 24, 2009
    I don't know if it is recommended, but I used em during the primer shortage.
  5. Jayman

    Jayman Big Dummy

    Nov 3, 2002
    Chantilly, VA
    The load you are using is .1 higher than the max load Hodgdon lists on their webpage. If you're going to switch to magnum primers, I'd back that load off a bit, as you're already out in un-charted territory. Do you really need 1000+ fps from this load?
  6. IndyGunFreak


    Jan 26, 2001

    Obviously, it depends on what bullet you're using, OAL, etc.. but if you're loading a 180gr FMJ, they are over what Lyman says already.

    The 40, is one of those rounds that I just don't play around with. It's already high pressure enough. *Most* of the data I've read where people tested the difference between standard and magnum SP... it was around 30-60fps... Plus you did it w/ Titegroup? Man, I'd probably be sitting w/ the bullet puller for a while if it were me.
  7. kimberguy2004


    Jan 14, 2007
    Austin, Tx
    I use them on .40 & 9MM with no problems, but my loads are not even near the top of the scale. I load for a power factor and when the chronograph says I'm there, I stop. I see no need to impress anyone at the range with how much punishment me or the gun can take. If I'm really feeling masochistic, I have a FA .454 and a couple of .44s I can play with.
  8. dudel


    Dec 10, 2008
    Texas Hill Country
    +1 Changing components, running near maximum. If you're not working with a chrono under those conditions, you're just asking for troubles. (yes, plural)
  9. sonick808


    Dec 29, 2009
    Chandler, AZ, US
    it's of negligible consequence. Unless you're running max loads already, just use your regular recipe. If you can't stand it psychologically, knock off a tenth of a grain, but it won't matter.

    The funny thing about loading pistol is that you're usually using a powder thrower instead of a trickler and a scale; there's not a powder thrower in existence that doesn't have a margin of error of at least .5 grain each way. Backing off ".1" is pointless unless you're using a trickler and a scale for each charge.

    Keep an eye on your recipe, i re-read and saw someone said you were above the lyman max load; that's where things like magnum primers start to matter. The chronograph doesn't really tell you much about the max psi in your gun. you've got set back, oal, charge compression, the 180 grain pills that shouldn't really be used in .40SW anyway, and other variables. Might want to back off and find a middle of the road recipe. Use the chrono less as a meter of load safety and established data more.
    Last edited: Apr 5, 2010
  10. ron59

    ron59 Bustin Caps

    Jan 3, 2009
    Smyrna, GA

    Sorry, but I'm gonna have to dispute this. My 550B in no way has this wide of a margin of error. In fact, whenever I start for a session I check it, and may have to adjust it .05grain (that's half of .1gr), but that's about it.
    It does NOT vary during a session, and I only check it every few hundred rounds... and usually don't even need to touch it.

    I don't know what crappy reloader you're using, but .5gr each way would be a powder thrower in the garbage can for me.
  11. I agree with Ron59. My Lee powder disc is so consistent that I check when I change powders or CC hole, then it balls on accurate every dump. I have only been reloading for 6-8 months now and have ONLY used Magnum primers (the only thing I could find) and don't run to max loads with any powders, they have been fine. I have read the same thing Indygunfreak said 30-60 fps, which I like to make up for my shorter barrel 27. I will continue to use them because they are $20/1k cheaper and usable.
    Last edited: Apr 5, 2010
  12. jing1117


    Oct 10, 2008
    Roseville, CA

    Sorry, but in my experience the dillon 550, hornady lnl, lee pro 1000 disk system throw very consistent loads - especially when I use powders such as Win WST, WSF, 231 - even with flake type powders I have never gotten a .5 variance. they are all within the .1 variance if that. If something is not right I check everything. The .5 variance can be a lot to some powders - especially running near max loads.

    Going back to the topic - Yes I have used small pistol magnum primers in loading .40. I just started from the bottom of the loading data and worked it up.
    Last edited: Apr 6, 2010
  13. Hoser

    Hoser Ninja

    May 22, 2002
    So what your saying is that if I want to throw 4.0 gns of N320 I could expect anywhere from 3.5-4.5 gns?

    If that is what your powder measure throws you need a new powder measure.

    I have measures made by Dillon, RCBS and Harrel. None are anywhere near as bad as yours. Maybe .1-.15 either side of what I am looking for.
  14. Hoser

    Hoser Ninja

    May 22, 2002
    No issues at all. Back off your load a bit and chrono your ammo.

    Heck I use small rifle primers.
  15. professor gun

    professor gun

    Dec 18, 2007
    I use an RCBS powder measure that varies about 0.1 grain charge to charge with pistol powders I use.

    I have read that mag primers burn hotter and may increase pressure a bit so the advice above on decreasing from max is very good I think.

    My experience with the .40 is that it is not as tolerant of changes as other calibers (.45 ACP).
  16. sonick808


    Dec 29, 2009
    Chandler, AZ, US
    i've tried throwing mostly flake via rcbs, hornady and lee throwers; weighing the charge with a diamond scale calibrated on US standards weights.

    I suspect some of the above accurate charges may in fact be indictments (or increments) of inaccurate scales but if you ARE getting +_ .1gn, don't EVER get rid of that thrower.

    funny thing: lee was the most accurate. ha
    Last edited: Apr 6, 2010
  17. arkdweller22

    arkdweller22 Cuhootnified

    Dec 26, 2008
    With regard to velocity, pressure, etc.: Typically it makes very little difference if you're using Magnum primers as opposed to standard.

    Like others, I have used Magnum primers during the ammo shortage and did not need to change my recipes.
    I did note, however, that Magnum primers (at least the Winchesters I was using) are a bit harder than standard. Thereby causing occasional failures to fire due to light primer strikes, especially with mouse guns.
  18. TexasFats

    TexasFats NRA, TSRA, SAF

    Sep 14, 2006
    Austin, TX
    The priming composition in magnum primers is hotter and throws more "fire" into the powder. A lot of it depends on what powder you are using. Ball powders may need magnum primers just to fire reliably. Flake powders may burn too fast with them. Back off and work up slowly.