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Reloading Techniques For Reloading


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Similar burn rate

 
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  #8  
Old 08-25-2013, 11:51 AM
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Re: Similar burn rate

Quote:
Originally Posted by Iclimb View Post
Thanks for the info. How so?
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.
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Old 08-25-2013, 04:32 PM
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Re: Similar burn rate

"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.
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  #10  
Old 08-25-2013, 05:17 PM
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Re: Similar burn rate

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Originally Posted by boomtube View Post
"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,
This chart index's the rates fairly well....

http://www.accuratepowder.com/wp-con...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.
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  #11  
Old 08-25-2013, 06:27 PM
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Re: Similar burn rate

read the little red line at the bottom of the chart...

http://www.accuratepowder.com/wp-con...burn_rates.pdf
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  #12  
Old 08-25-2013, 06:40 PM
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Re: Similar burn rate

Quote:
Originally Posted by Lefty7mmstw View Post
read the little red line at the bottom of the chart...

http://www.accuratepowder.com/wp-con...burn_rates.pdf
Yup, a standard disclaimer.

Back to the question....

Quote:
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.
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  #13  
Old 08-25-2013, 07:05 PM
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Re: Similar burn rate

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
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  #14  
Old 08-25-2013, 07:10 PM
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Re: Similar burn rate

Quote:
Originally Posted by MontanaRifleman View Post
Yup, a standard disclaimer.

Back to the question....

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.
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