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SAAMI says 11,500,

Discussion in 'Shooting Related Threads' started by mrskeet410, Apr 4, 2011.

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  1. mrskeet410

    mrskeet410 TS Member

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    SAAMI says 11,500 psi is max for 12 gauge 2 3/4 inch loads, but "Reloading Experts" and conventional wisdom says over 10,000 psi is high pressure. Why is that?
     
  2. jdsfarms

    jdsfarms Well-Known Member

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    Because at that point only a small thing has to happen to make it a dangerous load,powder drops vary in all loaders for different reasons,at that point an extra half a grain of powder can cause dangerous pressures in a maximum load,if you weighed every charge of shot and powder it may be different.Jerry
     
  3. chipking

    chipking TS Member

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    You answered your own question mrskeet410.
    SAAMI says 11,500psi is MAX

    anything over 10,000psi is HIGH (Note not MAX just HIGH)

    When you get within 1,500 psi of your MAX it does not take a lot of change to exceed it. Deeper crimps, a few tenths variation in a charge (either shot or powder), a hotter than normal primer in a batch.

    Will it cause a problem? Who the heck knows but I would rather have a wider margin especially if I can get the performance I want with a 3,000 psi margin for error.

    --- Chip King ---
     
  4. Pull & Mark

    Pull & Mark Well-Known Member

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    While I'm no expert, I look at it this way. A target shooter who is ave or slightly above ave can shoot 8 to 10 thousand rounds a year. Now after 10 years thats a lot of little explosions in his/her barrel. 10 seasons of hard shooting during the worst part of summer can really heat up a barrel. High heat can cause the metal to temper, get britle, cause fatigue. This weakens the barrel over time. Until one day the barrel fails. Now since this barrel is going to be in my hands why would I want to push a load 80,000 or l00,000 times in my hands. Most of us pick a load and use it for years. Lower pressure loads will help my firearm work longer with less trouble down the road. I've seen the results of hands, fingers and forearms after barrels blow-up. I'm not going to tempt fate. It costs very little to nothing to do this. Have you seen the results of a blown barre??? Now what do you want to do??? Break-em all. Jeff
     
  5. mike campbell

    mike campbell Active Member

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    C'mon people...SAAMI max is the SUGGESTED maximum average working pressure...the "service pressure." That's the pressure that a modern firearm is expected to digest, day in and day out for THOUSANDS AND THOUSANDS of rounds without undue stress.

    That's the suggested maximum AVERAGE and, since SAAMI allows a +/- leeway of 1,000 psi in it's reference ammo, that means individual shells in a factory lot may generate pressures as high as 12,500 psi.

    I'm not suggesting you ignore the SAAMI max, that's why 10,000 is often suggested as a reasonable target. Use a published load in that region and you're highly unlikely to get in trouble from an indavertant substitution. The powder manufacturers list many loads at 11,000+....because they're safe.

    The speed limit is 55 mph....how many of you drive at 54?
     
  6. Jim101

    Jim101 Active Member

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    Mash on the link and you can read all about the SAAMI standards.



    Jimmy
     
  7. dverna

    dverna Active Member

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    Mr. Skeet,

    Some people wish to push the envelope even when there is no need to. Frankly, I do not understand why they think that way.

    Those you label "experts" have made a decision to select loads that provide an added margin of safety when a choice is available. This should answer your question.

    Any reasonable person looking for a load that delivers say 1200 fps will select the one that develops less than 10,000 psi over one that approaches 11,500. To argue otherwise makes the "champion" of higher pressure look either ignorant (fixable) or stupid (usually a lost cause).

    It is not necessary to be an "expert" to exercises common sense.

    Don Verna
     
  8. oleolliedawg

    oleolliedawg Banned User Banned TS Supporters

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    Mahlon Schwar fired at 334,800 Registered Singles and countless practice targets through one old Model 12. So much for the theory on barrel fatigue!!
     
  9. skeezix

    skeezix Member

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    There are different kinds of metal fatigue. Low cycle fatigue is caused by straining the material above the proportional limit a number of times. Low cycle fatigue is generally less than 10,000 cycles. High cycle fatigue is an elastic failure. Repeated stress cycles well below the yield strength of the material will eventually result in a failure. High cycle fatigue curves are generally published out to about 10 million cycles. I've forgotten which is which - but the fracture surfaces of these two different fatigue failure modes are distinct and different. A gun with 300,000 loads on it has probably survived any low cycle fatigue issues - although if one shell in a 100 is a hot load, it may be at about 3,000 damaging cycles - and on the verge of failure. it hasn't really got into the range of high cycle fatigue yet. I believe there is also something called intermediate cycle fatigue - which I've never studied at all.

    I think fatigue is an issue to be considered - but I wouldn't loose a lot of sleep over it. Still, two loads with similar performance - I'd opt for a lower pressure load.

    I also agree that as sensitive as some loads are to drops - a little margin on your design load is nice to have. Because when you screw up - it may not be quite so catastrophic as it would be if you screwed up a max load,

    John
     
  10. jdsfarms

    jdsfarms Well-Known Member

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    Why would you load an 11500 psi load with red dot when you can get the same velocity at a much lower and safer pressure simply by changing to say green dot?Both powders cost the same and you could probably find a recipe that used you existing components(primer,wad,hull)Jerry
     
  11. Quack Shot

    Quack Shot Active Member

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    Don't take it from me, but ask yourself a question. Are you able to EXACTLY duplicate the ammunition that Alliant, Hodgdon, or Lyman tested? Same Lot numbers? Are you going to fire that ammunition under the exact conditions present at the time they were tested? Is it a reasonable assumption to expect some variation from what they were able to load and test? Do you really expect that if you assemble ammunition using the data listed, that you will obtain the same results if your creation was tested? Look at the disclaimers preceeding your access to loading data at the two larger powder companies and see what they say. I'll paste it below for your convenience. Below that you will find a couple of links to some documents from HP White Laboratories. If you don't know who they are or what they do, check them out for yourself. Read the documents and you may find that a steady diet of maximum loads might be a risky proposition. I don't really fear the one or two boxes of slightly over max loads. I look at the 20,000 or more shells someone might fire over a years time. A real eye opener might be to have some of your pet loads tested for pressure and velocity under the exact conditions you would be shooting under.



    This is from the disclaimer on the Alliant Data "Agreement Page":

    "The information displayed on this site, including ballistic data, was derived from tightly controlled laboratory conditions. This information and data may vary considerably depending on many factors, including the components used, component assembly, the type of firearm used, reloading techniques, safety precautions practiced, etc."

    "Alliant Powder expressly disclaims any and all warranties with respect to any and all products sold or distributed by it, the safety or suitability thereof, or the results obtained including, without limitation, any implied warranty of merchantability or fitness for a particular purpose and/or any other warranty. Buyers and users assume all risk, responsibility and liability whatsoever for any and all injuries (including death), losses or damages to persons or property (including consequential damages), arising from the use of any product or data, whether or not occasioned by seller's negligence or based on strict liability or principles of indemnity or contribution. Alliant Powder neither assumes nor authorizes any person to assume for it any liability in connection with the use of any product or data."

    "The individual accessing this site assumes the risk of safe loading practices.
    Failure to do so could result in severe personal injury (or death) and/or property damage."



    Here is the same stuff on the Hodgdon site:

    "The information displayed on this site, including ballistic data, was derived from tightly controlled laboratory conditions. This information and data may vary considerably depending on many factors, including the components used, component assembly, the type of firearm used, reloading techniques, safety precautions practiced, etc."

    "Hodgdon® Powder, IMR® Powder and Winchester® Powder expressly disclaim any and all warranties with respect to any and all products sold or distributed by them, the safety or suitability thereof, or the results obtained including, without limitation, any implied warranty of merchantability or fitness for a particular purpose and/or any other warranty. Buyers and users assume all risk, responsibility and liability whatsoever for any and all injuries (including death), losses or damages to persons or property (including consequential damages), arising from the use of any product or data, whether or not occasioned by seller’s negligence or based on strict liability or principles of indemnity or contribution. Hodgdon®, IMR® and Winchester® powders neither assume nor authorize any person to assume for it any liability in connection with the use of any product or data."

    "The individual accessing this site assumes the risk of safe loading practices. Failure to do so could result in severe personal injury (or death) and/or property damage."


    Here are a couple of documents from HP White Labs on firearms failures. I have referenced these many times on this forum, but some people simply can't read. These are written by the people that work with firearms forensics and testing, among other things. There are references to the cause of firearms failures, including catastrophic failures. Listed in these two documents are some references to repeated stressors of firing numerous maximum loads over a period of time. Check pages 6 and 7 in the first file and start on page 1 of the second. If you need clarification, call them. They may talk to you about it in detail. I had some of these discussions with people over there well before their last aquisition and merger. Learned a lot about firearms failures and ammunition testing and proper loading practices.

    <a href="http://www.hpwhite.com/uploads/file/100-00.pdf" target="_blank">HP White PDF 100-00</a>

    <a href="http://www.hpwhite.com/uploads/file/101-00.pdf" target="_blank">HP White PDF 101-00</a>


    If you run your car at 150 MPH all day long, weeks or months one end, with your engine near or slightly over redline, how long will it last compared to one that was run a little more conservatively? A car made for racing would be perfect if it fell apart right after crossing the finish line. The idea behind a firearm is not to push the limits so a failure occurs. A little common sense and conservative practices can go a long way to help provide a little headroom for error. Thinking of a ten percent variation, take ten percent from the max of 11,500 PSI and that should be your limit with a built in margin for error and normal variables. I round it down to 10,000 PSI or less for any load that will be used in any substantial quantity. If substituting components, the limit goes downward according to what the substitution is.
     
  12. scooterbum

    scooterbum Active Member

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    I believe a shotgun barrel is designed in strength to withstand a steady diet of 11,500 psi loads. Sammi has determined that this is acceptable. Less pressure might help to keep your gun tighter, longer. But, 11,500 is deemed to be safe.

    Rifle shooters customarily take their rifles to the limit. No damage. But there is a price to pay, in wear.

    I think some of the problem with shotgunners is that their gun might be light in weight, and they might think that the gun is kicking them. They might think that this is pressure related, or that their load is getting stiff. But run a heavier gun, and you won't notice a 1255 load at full pressure.
     
  13. scooterbum

    scooterbum Active Member

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    The barrel wears out, and then we replace the barrel. There is no safety infringement.
     
  14. leadvail

    leadvail Member

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    Lets see, Proof loads are 18- 20,000 psi, factory loads are 12000 psi, loading manuals say 11,500 psi is ok (with no warning to stay at 10,000 psi or below)...hmmm

    Is there really a cushion of safety from 10,000 to 11,500 psi?

    Many things to ponder grasshooper.Where is yoda when you need him.


    Personally, I use published data from the manuals written by the professionals with the load that gives me the performance and efficiency I desire no matter the psi others say I need to be safe. Some are 6000psi, some are 11,500 psi.

    Are some folks better off staying in lower limits if they don't have a scale and use it randomaly checking their powder and shot drops and have worn guns? Naw, for those folks there is no safety net low enough for them anyway.

    Bob
     
  15. timb99

    timb99 Well-Known Member

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    You_CAN_drive your car in such a manner that the tachometer reads just under the redline all the time.

    The engine is designed to operate at that speed. Right?

    But why would you?

    I call it being conservative.

    For me anyway, if I can formulate a load that does what I want it to do (payload, muzzle velocity, and complete combustion), at 8,000 psi or 10,000 psi, why would I go out of my way to find one that does exactly the same thing with a higher pressure?

    Here's a fact. Everything will fail. Always. Its just a matter of time. If pressure doesn't get it, corrosion will. Why accelerate it?
     
  16. leadvail

    leadvail Member

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    I dunno, my wife's 1979 TM1 hasn't failed yet.

    In reloading, I wonder exactly how much more gun life will you experience shaving those 1500 psi off?
     
  17. SevenMaryThree

    SevenMaryThree Member

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    Take a look at some of the pressures for 28 ga. loadings.
     
  18. hmb

    hmb Well-Known Member

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    If the flame coming out the end of the barrel exceeds one foot in length it is time to reduce the your load. HMB
     
  19. 22hornet

    22hornet Well-Known Member

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    If the flame coming out the end of the barrel exceeds one foot in length it is time to reduce the your load. HMB

    Unless, of course it's some of the "Annie" loads I've seen...KaBOOM!
     
  20. timb99

    timb99 Well-Known Member

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    Really slow powders can cause long flames. This may not necessarily be due to high pressure.
     
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