Max Loads - How Close to Pmax

Discussion in 'The Ammo & Reloading Forum' started by Caneman, Jan 8, 2011.

  1. Caneman

    Caneman Active Member

    Oct 22, 2010
    I have been keeping my loads to no more than 90% of Pmax (predicted by QL, and checked to make sure the load is within the loading manual values), and avoiding any loads that are more pressure than this.

    Just wondering how close can I go to Pmax and be safe?

    How will I know a load is not safe before it blows up my gun? :confused:
  2. 312shooter

    312shooter Well-Known Member

    Mar 17, 2008
    Las Vegas NV
    Why entertain the idea of exceeding this? Sorry to answer with a question but exceeding lab tested data is where you should stop, let the lab testers figure out when a gun blows up. This is similar to asking how close can I drive to the cliffs edge before I go over.......?

  3. gschnarr

    gschnarr New Member

    Sep 27, 2009
    +1 for 312shooter. With max loads, you shorten the life of the brass, put more wear on your barrel and action, and your most accurate load is by far the most often in the mid load range. As for pressure, there are the usual signs on the brass and primers. Also this is where a chronograph is essential. QL is what generally happens. With every rifle, your results will often be different sometimes a LOT different. I work up my loads for the accuracy I need and with the use of my Chrono, it is easy to calculate trajectory and what I need to do in different circumstances and at different ranges. If you need or want a faster or more powerful weapon, get a cartridge and weapon combination which is made to offer what you want. It is a lot safer. Remember that safety is critical.
    Last edited: Jan 8, 2011
  4. Boris

    Boris Former Guest

    Oct 1, 2010
    If you are loading from a SAAMI manual, then so called max pressure loads can be shot all day long as long as you work your way up just to make sure.

    Now if you are shooting loads from a CIP loading manual then I would keep it a little below their max loads. I have a CIP manual that has several starting loads that exceed SAAMIs so called "max" loads. SAAMI loads are pretty anemic at best.

    To get your gun to blow up you would have to go well beyond any published data. There is no need to push it that far............
  5. TheGunClinger

    TheGunClinger Well-Known Member Supporting Member

    Loaded question there, excuse the pun, but why are you concerned about overmax loads? I am very far from being an expert on this subject but I am used to going by my manuals and never exceed max loads. Actually I dont even go to max. I stick to middle of the road on any of my loads. I like recoil but I dont really enjoy a blown up gun. I agree with 312shooter 100%.
  6. Caneman

    Caneman Active Member

    Oct 22, 2010
    Thanks for the good responses, I appreciate it... Just to clarify, I am not interested in exceeding SAAMI max pressures. Thanks for explaining that SAAMI max pressure is conservative, I did not know that.
  7. muddober

    muddober Active Member

    Sep 19, 2008
    Carson City Nevada
    Lets first talk handgun ammo. What usually blows up a gun is not so much hot loads as being stupid by using too much of the wrong powder. As an example using a fast burning powder like Bullseye it is real easy to blow a gun up with a double charge, where as if you overloaded with 2400 you would start to see some high pressure signs long before you blew up the gun. Sticky cases and primer firing pin marks showing cratering.

    Some of that can be said for rifles except that if you are doing as you should be and utilizing a powder that the burn rate dictates that you almost fill the case you will probably never blow the up the gun before you would see pressure signs like hard bolt removal and primers blown clear out of the pockets. Modern bolt action rifles are amazingly forgiving for high pressure loads most auto loaders and lever guns are not. When I was a kid working in a gun shop an idiot brought in a 98 Mauser that had been rebarreld to 458 Win mag. He had ran low on IMR3031 so he mixed Unique with it, his reasoning, they were both black. You could not open the bolt and you could actually see brass that had started to flow from around the bolt. I finally got the bolt out of at the cost of the extractor. I replaced the extractor, checked out the head spacing which was perfect and sent him on his way.

    You should know that all reloading manuals from about 1970 on are very conservative (lawyers made them that way) and many published max loads in later manuals can be exceeded with caution. Where as several of the early ones will show pressure signs long before you reach their published max loads and they really need to be approached with caution. As an example when the 357 mag was first introduced in about 1935 it was loaded to 44,000 psi. Today every loading manual I have encountered that shows pressures for their loads show all max loads at less than 40,000 psi. In 1935 the 357 was a N frame gun which at the time was the biggest and baddest gun on the planet. Since then the manufacturers have built alloy light weight guns that in my opinion should never see over 30,000 psi.

    Through the 50 + years of reloading, I have caused and therefor experienced all of the pressure signs I have described herein, but I have never hurt myself or ruined a gun.

    I hope that was of some use to you.

  8. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    Lever guns and excessive pressure loads:

    Years ago while at the range an older shooter arrived with a brand new Italian clone of a Henry with a highly polished brass frame. The guy was proud. His first shot at 50 yds was dead center on the bull. The second shot locked up the gun (??). He had disregarded the reloading manuals and loaded 45 long colt ammo to 44 magnum maximum levels. I saw him a few weeks later, again at the range. He had to take the gun to a gunsmith to get it unlocked and cleared of the fired case. The excessive pressure warped the frame (its Brass!!) so that it no longer would feed ammo and he had to shoot it as a single shot. That's Stupid!

    Reloading manuals test loads and tell you what is safe. There is no reason to exceed the loads listed there. If you need more power then buy a bigger gun!

  9. woolleyworm

    woolleyworm Well-Known Member

    Feb 23, 2009
    SW Fort Worth
    A listed Max Load is one that is PROVEN SAFE, so there isn't any need to worry about a gun blowing up if you're going to fire it all day long as earlier stated. What you do have to worry about is this :

    1 - What was is proven in? test barrel length, equivalent to what you're going to be shooting?

    2 - Have you worked up the load properly, step by step? If you have, you'll know where the max is at for your gun. Your max may be determined as simply as finding a load in the min-mid range that shoots great. If you hit a peak and then subsequent hotter loads shoot worse, then why bother working the load up any further; you've arrived at your goal.

    3 - Are you looking for signs of over pressure ( and underpressure for that matter also ) hard extraction, flattened/deformed primers, etc.

    Proper load development EACH and EVERY time with a new load is what ensures a reloader safety and a guns continued performance.
  10. Caneman

    Caneman Active Member

    Oct 22, 2010
    Thanks, that helps me to understand why different manuals will have different max loads, they are specific to the rifle/bullet/conditions they tested. I have seen these loads differ quite a bit from manuals published by bullet, powder, and reloading equipment manufacturers.

    Another question about percent fill of the cartridge.... What is the minimum amount you want the cartridge to be filled and the maximum (I have read between 80% and 105% but I don't know if these are correct)?
  11. muddober

    muddober Active Member

    Sep 19, 2008
    Carson City Nevada
    Caneman, think about it for a minute. Lets suppose they made a powder that it took an amount only the size of a BB to propel a bullet from the case. Now just imagine how that small amount of powder would react if it was close to the bullet as if you were shooting down hill and then how different it would react if you were shooting the gun up hill and all the powder was near the primer. To get the best performance in accuracy consistency in ignition is paramount and the only way to insure that the powder is always close its ignition source the primer, is to choose a powder that fills the case as much as possible so there is never an air gap between the primer and powder, even to the point of having to compress the powder provided you can get the bullet seated properly.

    I hope that helps you,

    Last edited: Jan 9, 2011
  12. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    While loading to full capacity of the case may prove to be more repeatable do not exceed the maximum loads listed in the reloading data.

    Loading compressed loads can be problematical. If over compressed the pressure of this may move the bullet forward in the case, changing the cartridge overall length randomly between the loaded cartridges especially if no crimp is used (no crimp is a typical practice for bolt guns). I avoid compressed loads for that reason alone or use a LEE Factory Crimp Die on those loads.

    This concept of 100% fill works fine in rifle cartridges but the theory can fall apart for pistol cartridges and some powders. For powders like Bullseye and W231 and the exact same Hodgdon powder HP38, the cases are not anywhere near close to full. For some powders it makes a difference and some it doesn't (???). Those two powders (W231/HP38 and Bullseye) are probably the most used powders for handguns in the USA. If they gave inconsistent results I don't think that would be the case.

    In a magazine column from the last few years the writer apparently taught some kind of handgun shooting class. One of his "tricks" was to chronograph two identical cartridges loaded by him in the class and shoot them at the range. The velocities were greatly different. What he did during the shooting was in one case elevate the gun before shooting so as to move all of the small amount of powder to the rear of the case and in the other case he lowered the gun to move all the powder to the front of the case. Whatever that powder was it was grossly effected by powder position. Is your favorite pistol powder so effected?

  13. Caneman

    Caneman Active Member

    Oct 22, 2010
    Ron, that makes sense, thanks.

    LD, not sure if my powder is affected like that. For pistols, I am reloading for a .357 using H110, been playing around with 16.0-16.5 grains for a 158 gr jsp... this is one reason for my question about max loads. I am trying to develop a self defense load when hunting on public land... I have had this Ruger GP100 .357 mag at home for quite a while for self defense, and research indicated it could be a decent hunting round as well so I set out to see what I could develop. Where I hunt on public land I need a load for self defense against small black bears, mountian lions, and two legged predators that want to cause trouble. From my research, a .357 mag using a 158 gr jsp bullet with high velocities will be fine, so I am trying to get as much as I can out of it. My chrony showed 16.5 gr gets me 1250, but that is about 90% of max pressure, and some loading manuals show the load can go up to 17.5 gr.

    With rifles I have noticed that there will be an accuracy node predicted at the low, middle, and high end of the pressure range. I have wanted to see if I could load that high very near the max SAAMI pressure, but I have not done this yet. Where I hunt it can frequently be 90-100 degrees F in late Sep or early Oct and I was afraid that the powder would over pressure if I loaded it near P max due to the eleveated temp. Now with Varget it supposedly will not do this, so I have been experimenting with this in my load development. So those are the two reasons why I was asking about loading right near Pmax.
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