Similar burn rate

Discussion in 'Reloading' started by Iclimb, Aug 24, 2013.

  1. Iclimb

    Iclimb Well-Known Member

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    Can powders of similar burn rates be substituted? My book only list ramshot Magnum was wanting to use something else. I.e can I take 10% out and start working up?
     
  2. SidecarFlip

    SidecarFlip Well-Known Member

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    Anything is possible. Thats what the cross drilled holes are for in your receiver. I call 'em stupid holes. They are there for the sole purpose of an exit for stupid loads. That way the rifle don't blow up in your face......:)
     

  3. venatic

    venatic Well-Known Member

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    I have never seen a manual that only listed one powder? More info?
     
  4. Iclimb

    Iclimb Well-Known Member

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    Gun guides 25-06 Seirra 120's. just was. Curious how powders of similar burn rate corresponded to pressures. I'll see if someone will run a quick load for me.

    I got a Box of nosler accubond 180's for 30-06 and the card it came with only lists re-22, gun guide doesn't list nosler....
     
  5. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    I'd be a heck of a lot more worried about swapping powders than bullets as that'll get you into trouble a lot faster. Go to the alliant, accurate, or hodgdon websites for loads for the bullet weight and caliber and start down your 10% once you have a load for your powder in the bullet weight.
    I've done quite a few workups with non-canister/ mli surp. powders and new powders as they come to the market. It isn't for the faint of heart and you need to do your homework before you pull the trigger. Advanced loading to be sure and just as dangerous as initial load workups with a wildcat.
     
  6. MontanaRifleman

    MontanaRifleman Well-Known Member

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    The answer is yes. I will always try to research data as much as possible but there is very little to no data in a lot of combinations. Newer powders such as RL17 and now RL33 have very little published data to go by and in the case of 33 I don't know of any.

    I know that RL17's burn rate is very close to to H4350 which is a popular powder with lots of data and online recipes so when I started experimenting with it in different chamberings i looked for the H4350 data and recipes as a guide and started at about 10% lower than the max loads listed. The result were very predictable. With RL33, I know that it is very close to H870. I also know it's slower than Retumbo so the same charge of 33 for a Retumbo max load should produce lower pressure. To be safe I'll back off a little on that.

    You don't want to back off too far. An extremely low charge can be trouble too.
     
  7. Iclimb

    Iclimb Well-Known Member

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    Thanks for the info. How so?
     
  8. MontanaRifleman

    MontanaRifleman Well-Known Member

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    I am not an expert on the subject so I wont attempt to explain it here. If you do a search using combinations of the following words you will find plenty of hits on the subject.

    reloading
    light loads
    reduced loads
    detonation
    secondary explosion effect (SEE)

    Like most other subjects, it generates a lot of debate.

    Another thing you can do is contact both the powder and bullet companies for recommendations, especially the powder companies. They will probably be very conservative for liability reasons and may not venture to advise on load combinations they haven't tested.
     
  9. boomtube

    boomtube Well-Known Member

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    "Can powders of similar burn rates be substituted?"

    Sure. Who knows, you might even get lucky. But, how are you going to know if any adjacent two powders in the charts are similar burn rates?

    The book lists are simply given in order of burn at a specific pressure and there is no calibration or predictibality between chart steps. Two adjacent powders may over lap so much as to be nearly identical but the ones either side of them may have a wide difference. And, chart burn rates are NOT the same throughout all usable loading intensities,

    Jam any powder into a totally closed space - a stalled bullet momentarily jammed into the rifling for instance - and the rate of pressue increase skyrockets; that's what drives SEE problems.

    But, other than all of that, powder swapping is a simple thing to do.
     
  10. MontanaRifleman

    MontanaRifleman Well-Known Member

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    This chart index's the rates fairly well....

    http://www.accuratepowder.com/wp-content/uploads/2010/12/burn_rates.pdf

    Have you ever used a powder/bullet combo that there was no data for? If so, how did you go about it? Let's assume Quickload technology wasn't available when you first experimented with a new powder.

    Same question to all the other posters.
     
  11. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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  12. MontanaRifleman

    MontanaRifleman Well-Known Member

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    Yup, a standard disclaimer.

    Back to the question....

     
  13. Bullet bumper

    Bullet bumper Well-Known Member

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    If you have a cartridge with no published load data then you have to find a similar cartridge with similar case volume and calibre and use that load data reducing the starting loads by another 10 % .
    These are the powders that are close to Ramshot Magnum but it's only a rough guide .


    145. Hodgdon H1000
    146. Ramshot Magnum
    147. Alliant RL25
    148. Hodgdon Retumbo

    If you look at the Hodgdon data for a cartridge very close to what you have and bullet weight that uses Retumbo and match that against what you are already loading with Ramshot Magnum . Then a good comparison should emerge . Reduce that by 10% anyway and you should not be in trouble as Retumbo is a bit slower anyway.
    The reason that greatly reduced loads can suddenly speed up is the amount of Oxygen inside the case and the fact that the small amount of powder is spread out more and the primer can set more off instantly.
    I don't think a 10% reduction of a recommended load is excessive I have done it before so I can't see a problem
     
  14. Lefty7mmstw

    Lefty7mmstw Well-Known Member

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    The biggest problem with a closed bomb test chart or even a simple powder rate chart is there isn't any real world data there to differentiate how powders act while being constricted differently, how much load is on them, how much pressure you will hit at peak, etc..
    A good example of two rather similar powders having differing burns in different calibers is rl22 and I7828. In my 7rem they are similar with 7828 acting slightly faster with mid weight bullets. In my 300 win I 7828 is slightly slower burning than rl22. In my 270 using identical charges (on the run up) of I 7828 and rl22 (since the books do) a top charge of rl22 loosened a primer pocket while I 7828 is a 1/2 moa load and well within pressure bounds. I've fired 200 of them in the last few years.
    A burn rate chart can get you in the right class of powder, but using it to approximate charges is downright foolish. A better route is to find data in a slightly smaller cartridge or data with a slightly faster powder and consider your starts from there. You need the constriction and basic loading of the powder to make any sort of educated guess. Also do not substitute ball and stick powders as the bullet weight and pressure slow the two powder types down differently.