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SAAMI pressures 10mm Auto... my foundings...

Discussion in '10mm Reloading Forum' started by g20addicted, Feb 21, 2011.

  1. g20addicted


    Aug 1, 2010
    By surfing around in this forum and also throught other sources, I came out with some considerations about the reloading of 10mm auto that I'd like to share. Please comment and tell me if something's not correct.

    - Max SAAMI pressure for 10mm Auto is set at 37.500 psi

    - Currently there is no official 10mm Auto +P cartridge. I suppose that the reason is that having a large primer, the case is not strong enough (the edges of the bottom are slim) to handle higher pressures.
    Is there any manufacturer that produces 10mm Auto cases with the small primer? Would it then be possible, with a small primer, to increase the max pressure?

    - It is agreed that is is NOT recommended to shoot full-power loads (that may exceed SAAMI pressure) in a stock "low-supported chamber" glock barrell, but to use an aftermarket more supported one.
    In this regard, I've noticed, in the Hodgdong reloading chart ( for the 10mm Auto, that:
    a) Even at max loads, you never reach the 37.500 psi limit
    b) At max loads, the slower the powder is, the lower the pressure is (as a rule of thumb)
    c) The IMR 800-X, still being the second-best together with the Longshot, is the one with the LOWEST max pressure. At full loads with 200gr ball, it is just 32.500 psi, so with 5.000 still to go. This means that with the 800-X you could "safely" go a bit higher than the recommended max loads.

    Any comments from you folks?
  2. Kegs

    Kegs Ol 8 fingers ;)

    Oct 26, 2009
    Cold side of conus
    This is about the third or forth time I have seen this brought up on this or the ten ring forums - and I've only been participant on here for a year and a half!

    YES, there are 10mm cases built with small pistol primers.
    YES, they are stronger.
    YES, they are sorta rare.

    Use the search function to help you find other threads.

    I like the idea, but 200xtp @1220 is good enough for me & my G29 and so far it's proven to be a safe load for my gun (with extended 4.45" bbl.).

    I can get that out of a standard large pistol primer equipped case.

    800x = lovely for the 10mm as long as you don't mind spending the time hand measuring powder charges.

    I like to be an artisan. Everything I shoot out of this gun is hand crafted.

    If Speer made a gold dot 200-220 grain at an affordable price ($20/100), I might consider going with those and driving them faster. I don't think the 200 xtp can take much more than 1250 or so before being ripped up by bone. It's just not hard enough.
    Last edited: Feb 21, 2011

  3. _The_Shadow

    _The_Shadow Ret. Fireman

    Jul 23, 2007
    Southeast, LoUiSiAna
    G20Addicted, Here is something’s to think about! (Just theory of my study)

    Yes the SAAMI pressure for 10mm Auto is set at 37.500 psi. (the method of testing pressure now is not the same as yester years PSI(strain gauge) vs. C.U.P. (copper crush). Do people exceed this? I believe they do! I don't have pressure testing equipment so I don't know if my loads are exceeding 37.5K specifications.
    With that said, the weak area of the brass(not all 10mm brass is the same) is just a head of the internal dish to form the web head(where lack of chamber support takes place) to form the case head and primer pocket. Many chambers are cut that leave this area less support and can lead to a case blow out, jetting the high pressure gases out and into the magazine well area.

    What factors besides lack of support play into a case being blown out?
    Guns (different designs. chamber specs) themselves may not lock up properly, wear of parts, spring etc., debris? In any event it seems that during peak pressure movement of the slide occurs which actually increases the unsupported situation. If that is indeed occurring, then catastrophic case failure can happen.

    Brass (all brass is not the same alloy or internal structure) We ask a lot of these small pieces of stamped metal, especially with repeated use of reloading. The stretching and reshaping in and of itself can change its characteristics. But even new brass can fail on its first firing with factory loads, I have seen many split cases.

    Powder charge, this has been known to vary from different types powder measures. Things like no powder or too much powder caused by any number of reasons, powder bridge in the drop tubes of the equipment. In the mechanized world of high production things can and do happen and even people make mistakes.

    In this small community of 10mm shooters and even smaller community of 10mm handloaders many seek the most bang for the $$$ ammunition.

    About small primer ammo…Federal Ammunition and others are producing 10mm ammunition which uses the small pistol primer...this is Non Toxic Primered ammunition which is used to lead pollution down in indoor range environments. Mostly Law Enforcement contract use. I have some recovered brass from this type ammunition that I am doing some handloads with, whether the web is any stronger it remains to be seen.

    In today's world lawsuits make or break companies, therefore what we term CYA (cover your *****ets) take president. Therefore the risk are lessened by having commercial ammo which is leaves some room for error as used in any gun of unknown condition! Handloaders have to accept their own risk, to their own guns, themselves and bystanders if so involved.

    Best regards and be Safe!
  4. _The_Shadow

    _The_Shadow Ret. Fireman

    Jul 23, 2007
    Southeast, LoUiSiAna
    About powders...burn rate(fast vs. slower) and gas yield per grain weight of powder used are factors to which performance is either gained or lossed trying to shove projectile "X" down various bores.

    As we try to duplicate something that has been said to work, we introduce our own set of variables to the equation, thus small changes can have different results!

    I know we all want as much velocity as we can get safely(the formula of weight @ speed = energy), however getting this velocity with 100% maximum reliability is way more important that a couple of extra feet per second.

    Keys which make big differences...
    Chamber tight vs. loose affect pressure curves over time thus affect velocity.

    Barrel length long vs. short affects velocity by the time which pressure acts on projectile.

    Rifling design and twist rate affect by friction to velocity. Lubrication and cleanliness of barrel surfaces will play a large role with performance.

    Projectile construction, diameter, bearing surface, gilding metal, alloys and their lubricity & strength will affect performance.

    An equipment used to take measurements, these are different from other peoples test and can be affected by many factors such as lighting conditions, bullet flight over optical eyes, battery conditions just to mention a few. Multiple test will rule out some of these deficencies.

    All of this is what makes this so excitingly fun...
  5. MakeMineA10mm

    MakeMineA10mm * * * * Millennium Member Lifetime Member

    Feb 13, 1999
    Central Illinois
    Your direct questions have been answered, so let me give you some information about your general questions:

    1. The 10mm Auto is a modern pistol cartridge and when it was designed (late 70s/early 80s), it was a core principle of it's development to load to maximum pressures right from the start. There is no +P ammo because standard ammo is already at +P pressures. Pressures are effected by many factors, but basically, the 10mm, when loaded to max, is as good as it gets within safety parameters.

    2. This concept gets confused/muddled because of the FBI load. The original concept was to make a very powerful cartridge and then only make STRONG guns which can handle that heavy load. Then the FBI came along and had it loaded down. Now, 25 years later, a lot of people forget the original concept the 10mm was designed around. Basically, most cartridges were designed and then a Magnum or "+P" version came along later. This often lead to changes in the casing, so the hotter version would not fit in the weaker/older pistols. With the 10mm, it is the opposite. The hot load came along first, and then the weaker load came out. The farther we get in time from the 10mm's introduction, the more confusing this becomes because new people get into the 10mm (or shooting in general) and do not have this knowledge or memory of the way the events went.

    3. The bottom line in regards to the loading manuals and the pressures they load to has to do with several factors. First, I disagree that the faster-burning powders tend to be loaded to higher pressure levels. What I've found is that the NEWLY RELEASED powder that they are marketing heavily at the time the loading guide is being published, is always loaded to the highest pressures. (This, in turn, makes it look like the newer powder is the most wonderful-performing powder to ever be available.) So, you're suspicions (I think) are correct that companies don't load to the same pressure levels with different powders in the same load, although, the conclusion you drew isn't necessarily a 100% correct conclusion that the faster powders are always loaded hotter.

    So, where does that leave us with the bottom-line question you asked? Well, I think the main reason many of us are here and experiment with these types of loads is because we think there is room for improvement over the published loads.

    HOWEVER, one must remember that there are problems like burn-rate changes from lot-to-lot variations. (800x made in one batch two years ago is likely going to burn different than 800x made this year from a different batch of ingredients.) I believe one of the main reasons 800x loads are so low in IMR's data is because they recognize that it meters very poorly in powder measures, and they've tested and found that the variation for volumetric-thrown charges is such that they need to load down by a certain amount to make sure we loaders don't go over the max charge when our powder measure throws a variation to the high-side. This means, if we're careful and hand-weigh each load, there probably is some room to increase the charges.

    BUT, prudent loading practices also means we must carefully check pressures. We do that through a chronograph and pressure-ring measurements and other pressure signs, and in fact, we should be doing this even when loading within the recommended loads or when changing from one lot number of powder to another.

    Being too casual about this and trying to draw conclusions and loading through those conclusions without proper testing, loading technique, and application of pressure monitoring is folly.
  6. g20addicted


    Aug 1, 2010
    Perfectly agree with your statements.

    Regarding this:
    Because of the hot loads came first, and then the weaker followed, is it that the Glock models (20 and 29) have been designed with the original hot loads in mind or were they designed (being "younger" than the introduction of the first hot 10mm) for the "second loads"?

    This is the crucial question then...
  7. _The_Shadow

    _The_Shadow Ret. Fireman

    Jul 23, 2007
    Southeast, LoUiSiAna
    The original Bren Ten all metal (stainless steel) were designed for the Norma cartridges...Back then data I have read showed 42,000 C.U.P

    Well Glock 20 came along shortly there after and then later the Glock 29 both should handle to 10mm in its true form at the 37,500 psi impulse. Some people have probably exceeded this more than a few times...some have had catistrophic failures as well.

    The original loads from Norma were said to be HOT with some mentioning then as being too Hot!

    200 grain FMJ's @ 1200 fps from 5.00" barrels
    170 grain JHP's @ 1370 fps from 5.00" barrels

    I shoot a 200 grain Hornady XTP which runs 1180-1200 fps from a 5.00" S&W 1006, but this round from my Glock 29 runs 1080-1130 fps using Wolff 21 lb springs & non-captured recoil rod system. 3.78" stock barrel. No FTF, No FTE issues and No swollen brass cases either...Asking for much more than this in my opinion, invites less reliability or undue wear and tear to the pistol.

    If someone wants more, there are other platforms to achieve more performance, guns with 6" barrels or longer. Heavy Revolvers, modified semi auto and carbines...

    It this round is loaded to the Maximum with no room for error and a bullet sets back for some reason during the self loading process then the area of safety is gone!

    Good luck!
  8. g20addicted


    Aug 1, 2010
    Anyway, before getting a kaboom of the barrell, I should get a smiled/cracked brass.... and if I reload that specific one, then I'll get the kaboom.
  9. MinervaDoe


    Jan 26, 2009
    San Jose, CA
    No, you are WAY off base. You can get a catastrophic failure from new brass.

    5/10,000 th of an inch of expansion (over the expansion shown by standard factroy loads) is maximum.
    If you have a smilie or cracked brass, you have exceeded safe pressure by a mile.
    Last edited: Feb 24, 2011
  10. MakeMineA10mm

    MakeMineA10mm * * * * Millennium Member Lifetime Member

    Feb 13, 1999
    Central Illinois
    All 10mm handguns must be made to handle the full-power factory loads, or the manufacturer is putting themselves in a horribly liabel situation. The originators of the 10mm made the point that all 10mms forever-more will have to be built solidly enough to handle the max-power factory ammo. The issue with Glocks is that the factory barrel has a generous chamber and feed ramp to comply with Glock's demand that reliability be job #1. Glock also doesn't believe in handloading, so if the brass bulges slightly over the feed ramp with hot factory loads (or handloaded equivalents), they don't feel that's a failure.

    Dornaus and Dixon used pressure-proof-test ammo that went over 50,000 psi. The max AVG. pressure for the 10mm is 37,500psi, which means some goes over and some goes under. The Norma ammo varied up to 42,000 psi, and some of that brass smilied in the Bren Ten... (FYI, they called it "PSI" back then, but I agree with Shadow that they mostly used CUP measurements back then and called them PSI -- rather inaccurately...)

    With very careful loading (hand-weighing charges), we can get that variation down to right at 37,500psi with maybe only 1000psi variation or so. One must remember that even though we like to think of gunpowder as a very uniform-constituted substance, the fact of the matter is, that one cartridge may get more granules with more deterrent coating than the next cartridge, and so forth... Some brass will be a half-a-thousandth longer and therefore will get an ever-so-slightly firmer taper crimp, and so forth... So no matter how carefully we load, there will be variations.

    Then, you have the excellent points made by the Shadow. If you have some bullet set-back, or a round that the bullet is a little long on (possibly engaging the throat, or at least reducing the jump to the rifling, etc.) pressures can change, irrespective of the quality or type of loading we're doing with the cartridges. That safety margin is important. If nothing ever went wrong, we wouldn't need it, but Mr. Murphy seems to always float in, right when we think we've got it all figured out and handled...

    Agree 100%. In all my reading here, I assure you, Shadow will not lead you astray... His results match up extremely closely to mine. Keep in mind that 1200fps with a 200gr XTP IS an improvement over the original Norma factory load of 200gr FMJ-TC, because the XTP, being a HP, seats deeper into the case than the Norma bullet. Therefore, we've enhanced (slightly) the original performance and do so safely only with careful loading techniques.

    M.D. is right on here as well about possibly getting failure on the first firing of brand new brass. I think M.D. meant to say 5/10,000th, not 5/1000 expansion. In the post he quoted (which is mine from the "All Forum Users Must Read This" thread) I said that IF you are using truly very high performance 10mm ammo (and I cite several examples), then you should NOT follow Waters' advice of loading heavier to the point of accepting up to .001" extra brass expansion. MY OPINION is that if you are using that really hot factory ammo as your referrence ammo, you should not add ANY expansion for your own handloads. I stop when I get to Old Win. Silvertip ammo expansion levels or Original Norma factory ammo expansion. (These are the two loads I use for referrence ammo.)
  11. nickE10mm

    nickE10mm F.S.F.O.S.

    Apr 13, 2004
    Wichita, KS

    Great post.