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Thread: What distinguishes the different powders other than burn rate?

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    Member northernalberta's Avatar
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    Default What distinguishes the different powders other than burn rate?

    I'm fairly new at this. I see all these makes and models of powder, IMR 4064, IMR 4350, H4831, RL19... etc etc... I found a site that lists them all in order of burn rate, and I gather you'd want to use the slowest burning powder in an ultra-magnum that's lobbing a heavier bullet out a long barrel. But IMR 7828 is listed as one of the slower powders, so why would it be one of the powders recommended for my 25-06?

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    Well there is burn rate but also differences in how much gas they produce, energy density of the powder. You have low volume powders that make large volumes of gas, bulky powders that make little gas, and everywhere between.
     
    Some powders need a higher operating pressure to burn efficient, some need less. Some powders like H110/W296 can acutely be dangerous without enough pressure, they can detonate rather than burning.
     
    There are single base powders, multi base powders, coated powders, assorted shapes of the powder granules. All these things and more affect how the powder burns, off gasses, and what kind of pressure curve it will make.
     
    Getting yourself a copy of ABCís of reloading is a very good idea, it covers a lot of this theory type stuff. We have had a couple very educational threads here too you could search out.
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    Put their pressure curve high on the list of differences.

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    Quote Originally Posted by northernalberta View Post
    I'm fairly new at this. I see all these makes and models of powder, IMR 4064, IMR 4350, H4831, RL19... etc etc... I found a site that lists them all in order of burn rate, and I gather you'd want to use the slowest burning powder in an ultra-magnum that's lobbing a heavier bullet out a long barrel. But IMR 7828 is listed as one of the slower powders, so why would it be one of the powders recommended for my 25-06?
    You need consider what is done to determine the burn rate.

    They have different coatings, shapes, and granule sizes, all of which determine the so-called burn rate.

    Chemically they may be all the same except for the differences in Single Base and Double Base.

    One might use a slow burning powder in 25-06 because of the expansion ratio, rather than case size.

    Normally I think of Slow Powders as suitable for large cases and/or heavier bullets. BUT, if the case is large, and the caliber is large too, you need a faster burning powder.

    It's my understanding that a given powder will not function/burn the same in different cases. Simply because the burn rate is faster or slower doesn't mean that you can always use more of less than of another. Although that seems to be the case, most of the time, and I've come to expect it.

    You get an idea from looking at loading manuals.

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    Thanks guys. I might check the library for that book.

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    Itís kind of an advanced question actuley. A good question but a bit like asking how a computer works, itís good to know how a computer works but not necessary to be able to work a computer . . . And by working it you over time figure out a bunch.
     
    Iíd say reloading isnít rocket science except it kinda is, but you donít need to be a rocket scantest to push the lunch button or make some very good ammo.
     
    Burn rate charts or anything like them are good tools but they are a very rough tool. You canít look at a chart and say hey E is right next to F so they must be about the same. You DO say E is next to F so now Iíll look up load data for F and see if itís suitable for the job Iíve been doing with E or not.
     
    Always stick to the published load data from a reputable source, then start low and work up. You happen onto a lot of this stuff a clue here and tidbit there as you go along making ammo. Stay curious, keep playing and making ammo, a year or two you look back amazed how far you have come and how much more there is.
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    One thing to take into consideration is the diameter of the size of the mouth of the case in relationship to the diameter of the case. When the case is a straight wall like say a 45-70 there will be less pressure building up (less restrictive) so a faster powder can be used in comparison to say a 257 Weatherby (overbore).

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    Quote Originally Posted by PRDATR View Post
    One thing to take into consideration is the diameter of the size of the mouth of the case in relationship to the diameter of the case. When the case is a straight wall like say a 45-70 there will be less pressure building up (less restrictive) so a faster powder can be used in comparison to say a 257 Weatherby (overbore).
    So a general rule of thumb is the greater the ratio of case diameter to bullet diameter, the slower the burn rate? That's what I'm looking for at this point, general rules of thumb. All my rifles are the bottleneck style anyway though.

    Couple months ago I made up a whole bunch of bullets using 50.0 grains of IMR4350 in .270 (130gr.), and found they placed very consistently 4 inches lower at 100 yards than factory ammo... thus teaching me my first lesson; don't load 50 bullets only to find out after 5 shots that it's not a good load...

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    Although 4 inches seems like a lot. There are other reasons why the bullets would strike lower, other than the velocity.

    It could be a good load if it is accurate in your rifle, and the velocity is up to parr. Maybe, you could get them chronographed.

    I agree, that loading 50 rounds without testing may not be a good idea.

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    Quote Originally Posted by northernalberta View Post
    So a general rule of thumb is the greater the ratio of case diameter to bullet diameter, the slower the burn rate? That's what I'm looking for at this point, general rules of thumb. All my rifles are the bottleneck style anyway though.
    Well kinda. Look at it as total volume of the case and full volume of the bore is the space you need to fill with pressurized gas by the time the bullet exits. The time is going to be similar but the volume you need to fill in that time will be much more with a larger caliner . . . larger caliber needs faster powder to be able to fill the greater volume in the same(ish) time.

    So rule of thumb would be more like, assuming similar case volume larger caliber will want faster burn rate, smaller caliber slower burn rate.
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    The "total volume of the case and full volume of the bore" as Andy mentioned determines the Expansion Ratio.

    A 45-70 has a HIGH expansion ratio. A 7mm Magnum has a Low Expansion Ratio. Did I get that right?

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    Quote Originally Posted by northernalberta View Post
    I'm fairly new at this. I see all these makes and models of powder, IMR 4064, IMR 4350, H4831, RL19... etc etc... I found a site that lists them all in order of burn rate, and I gather you'd want to use the slowest burning powder in an ultra-magnum that's lobbing a heavier bullet out a long barrel. But IMR 7828 is listed as one of the slower powders, so why would it be one of the powders recommended for my 25-06?
    By "recommended" IMR 7828, do you mean it was a listed powder? For instance in the Speer Manual? The Speer manual used to have lots of loads using IMR powders and just because they list a powder doesn't mean it is the best powder for a cartridge/bullet combo. Most manuals now list a most accurate powder and charge which is helpful. No sense re-inventing the wheel.

    Also, look at the velocities with each powder. Some powders tend to produce consistency and accuracy, but perhaps not good velocities. The Sierra manual is good for this. It lists both the best accuracy load and the "hunting load". Quite often, not the same powder. The hunting load is an accurate load, but with maximum velocity.

    Another consideration in using powders is its ease of metering in the powder dispenser. Maybe not a problem if you use an automatic powder dispenser, but throwing a charge from an old-school dispenser can be a pain with a stick powder like 4064. I used to use it exclusively for my 30-06, but once I discovered RE-15, I rarely use 4064. RE-15 is a finer grained powder that meters like fine sand and throws very consistent charges. Once I have my dispenser set, I never have to use a powder trickler to adjust the powder charge.

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    I distinguish powders kinda like this: Oh, it say's Alliant on the canister, I'm all set. Oh, it says something else on the container, I guess I'll have to put that back.

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    The 25/06 has a relatively large case for the size of the bore. Theres a lot of powder/pressure trying to get out a rather small hole. To go to the extremes if you took that 25/06 case and necked it down to a needle size hole you would have to use very slow powder to keep pressure from going really high even without a bullet in the case. Now open the neck to 416 and it's much easier for the powder/pressure to escape and you can use a much faster powder to get pressure up where it needs to be.
    Bullet weight is also a factor. The heavier the bullet the harder it is to accelerate. More resistance means more pressure from a given powder until the bullet starts to move so you need to use a slower powder for a heavier bullet. Heavier is relative to bore size. 120grs is heavy for a 25 cal but light for a 30 cal. I don't load for the 25/06 but I can see how IMR 7828 might work well with a heavy bullet.

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    You've got some really good advice already. One thing to be aware of is the steps between powders on the universal grand slam burn rate chart are not uniform steps. Some powders are very very very close to each other on the burn rate chart. A couple places over you might find a 50% change in burn rate between two adjacent powders.

    No, I don't have a reference or footnote on the tip of my tongue to share with you. Just because I have heard it three or four times doesn't mean it is true. Maybe AD or Smitty will know for sure.

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    Quote Originally Posted by swmn View Post
    You've got some really good advice already. One thing to be aware of is the steps between powders on the universal grand slam burn rate chart are not uniform steps. Some powders are very very very close to each other on the burn rate chart. A couple places over you might find a 50% change in burn rate between two adjacent powders.

    No, I don't have a reference or footnote on the tip of my tongue to share with you. Just because I have heard it three or four times doesn't mean it is true. Maybe AD or Smitty will know for sure.
    Oh yea itís true. Some are so close they are listed one way on this chart and the other way on another chart. Then (mostly in the slower powders) the one on line 30 may be closer in rate to line 39 than it is to line 29. They are certainly not proportionate or linear graduations in the placement.
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    Quote Originally Posted by ADfields View Post
    Oh yea itís true. Some are so close they are listed one way on this chart and the other way on another chart. Then (mostly in the slower powders) the one on line 30 may be closer in rate to line 39 than it is to line 29. They are certainly not proportionate or linear graduations in the placement.
    Yas indeedy.

    Not good to extrapolate loads, better to use DATA.

    With my level of experience, for sure.

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    another good reference as a learning tool for this is the Hodgdon load data website as it posts not only velocities but pressures at those velocities as well so you can see the pressure differences that given powders climb to while attaining similar velocities that other powders seem to achieve "easily"

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    Quote Originally Posted by back country View Post
    another good reference as a learning tool for this is the Hodgdon load data website as it posts not only velocities but pressures at those velocities as well so you can see the pressure differences that given powders climb to while attaining similar velocities that other powders seem to achieve "easily"
    Since so much has been covered, I will just add this to go along with what backcountry said; http://data.hodgdon.com/main_menu.asp

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    The numbers and letters on the can, sorry couldn't resist.

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