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Burn rate discrepancies

1K views 2 replies 3 participants last post by  showmebob 
#1 ·
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So I am experimenting with new loads for my DPMS LR 308, and I wanted to know the burn rate order of the rifle powders that I have on hand.
I looked in 3 different manuals and got 3 different answers.
What's up with that ?
From fastest to slowest; top to bottom; this is what I got.

1. IMR 3031 -------- 2. IMR 3031 ------- 3. IMR 3031
H Varget --------------- H 4895 --------- W 748
W 748 -------- ------ Reloader 15 -------- H 4895
H 4895 -------- -------- H Varget --------- H Varget
Reloader 15 ------------- W 748 --------- Reloader 15
H 4350 ----------------- H 4350 --------- H 4350
Reloader 19 ------------- Reloader 19 --------- Reloader 19

This may not look like much, but realize that some of these move through 15 to 20 spaces of other different powders that I do not own.

Column # 3 is the order that I expected to see, but the other two threw me.
Why the discrepancy ?
Which is correct ? or does it depend on things like case capacity, volume, load density, ect. ?
 
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#2 ·
comanche, Most burn rate charts are based on how fast powder burns in an open space. When contained in a cartridge, the volume of the case and the weight of the bullet determine actual burn rate .... which may be totally different that the charts.

Here's the best way to determine the burn rate in your cartridge with your bullet: Buy a Hornady 7th Edition reloading manual. The powder charges for each cartridge and bullet weight are listed in burn rate order from fastest to slowest. If you don't have a Hornady manual, use any manual and try to find a common velocity for the powders in question. The heaviest charge weight will always be the slowest burning powder compared to the same velocity for other powders. Likewise, the fastest powder will be the lightest charge weight for the same velocity.
 
#3 ·
Thanks Iowegan
I have been wondering the same thing. I have decided to try different powders for 380, 9mm, and maybe 357 in an attempt to clean up the burn a little. I have 3 charts and they are all different in burn times. This is a confusing hobby! Even the loading manuals all have different weights that tend to confuse newcomers.
 
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