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+P loads with reloading equipment!?

Discussion in 'Reloading' started by Gpruitt54, May 9, 2014.

  1. Gpruitt54


    Jul 18, 2012
    I am a bit curious about what goes into a +P load if done by a reloader. Not going to try it myself. But, can a home reloader make these loads (safely!)? The reloading books expressly warn against exceeding powder weights, so how does the ammo makers do this and how is it different with home reloading gear? Is it different cases, special powder, or what?

    I am sure this question has been asked thousands of times on this forum. So, sorry for rehashing a very old topic.
  2. F106 Fan

    F106 Fan

    Oct 19, 2011
    All that is required is a way to measure pressure and hobbyists have no such equipment.

    There is a SAAMI maximum standard pressure and, generally, +P will be 10% higher. All the ammo manufacturers need to do is a little math and a bunch of testing. And buy a LOT of insurance!

    Clearly, they need to account for ambient conditions, powder measure variations and a lot of other factors but, conceptually, there's nothing to it once they have a way to measure pressure.


  3. Jimmy10mm


    May 3, 2014
    Greenacres, FL
    For the home reloader, without the gizmos to scientifically measure pressure, going from recommended starting loads to maximum recommend, and then a grain at a time, watching for primer flattening and the like, would probably be how to go about.

    Not something I'd ever do either. I began reloading in the 1970s to load 44 magnum cartridges down to a level I could enjoy shooting them at. The factory fodder was too hot for my wrist and elbow. :)
  4. Gpruitt54


    Jul 18, 2012
    Interesting. So nothing special about the brass, only the powder required to produce the desired pressure.
  5. dougader


    Apr 17, 2004
    If you look at the Starline brass website you can read about 9mm and 45 auto +P brass. IIRC, the brass may be tougher, but also have less case capacity so in some cases just using +P brass can raise pressures a bit.

    Not all +P brass is treated equal. You have to research everything for your caliber, your brass, etc.

    The thing about reloading is that even if you use the same components as listed in a reloading manual, their maximum listed load may result in loads that are higher than SAAMI maximums for you, in your gun. Always start below max and work your way up.
  6. fredj338


    Dec 22, 2004
    Most ammo manuf do NOT use canister powders, but have their own blends made. So for the reloader, you are stuck with book data. There is the rub, one book says this is max, another is 1/2-1gr higher for max. So it will depend. If you can read pressures, understand the chrono data, then you can go over some book data to achieve +P vel.
    Last edited: May 9, 2014
  7. WeeWilly


    Nov 12, 2011
    There are some SAAMI +P specifications, usually with calibers that came along before smokeless powder (but not always). These +P pressures are usually 10% over max for the non-+P spec for that caliber.

    Some manufacturers publish load data for some of the +P specs. Hodgdon publishes loads for some +P caliber specs, so there is no problem using this data. You should use +P spec brass as some very old brass for the non-+P caliber may or may not hold up to the higher pressure (probably will).

    You will see some manufacturers use terms like +P or +P+ for ammo they make in calibers that don't have a +P SAAMI designation, all these guys are saying is the load may be over max pressure for a normal load in that caliber (40S&W seems to be a favorite for this kind of marketing hype). When they publish +P+ they are saying is "please buy us for a $1 a round we really need the money..."

    I have loaded over book spec on purpose and a few times by mistake, in the end you generally find out that the guys that designed these things in the first place knew quite a bit about the objective at hand and designed things to be optimized to that pursuit.
  8. rg1


    Aug 5, 2003
    While I'm not recommending anyone load into the +P pressure levels there is published data available for +P loading. I would only recommend using published data using the exact components listed and the exact overall bullet seating lengths. AND the most important safety measure is to ONLY use new unfired cases every time. Never multi-fired cases or unknown source brass. Your firearm should be rated for +P levels. Plus every powder charge should be weighed on a verified scale. I don't see the benefits to try to push a 45 ACP another 50 fps just to say you're loading +P or trying to push 9MM or 40 SW another 50-75 fps.
  9. WiskyT

    WiskyT Malcontent

    Jun 12, 2002
    North Carolina
    As a practical matter, reloaders can very often duplicate or even exceed +P velocities by using published non +P data. For instance, Speer/Alliant publish 5.8 Unique with a 124 JHP in 9mm. This is not +P data. But, I can assure you that the velocity will duplicate the 124 GDHP +P load all day long.

    Also, as others have mentioned, there is some true +P data published by reliable sources. The only +P data I have seen published is for 38 Spl and 45 ACP.
  10. DWARREN123

    DWARREN123 Grumpy Old Guy

    Jan 25, 2008
    Clarksville, Tn.
    Also remember that ammo producers get bulk or designed powders and can do things most reloaders can not.