Percentage of powder burned and accuracy

[jfseaman]

Could not find in search. To many other subjects.

QuickLOAD brings up this question. My 260 and 300WSM are very nice at their current loads. Low ES/SD and it's all up to me. My ES/SD in the 260 is higher than the 300WSM but still wicked accurate (of course an artifact of the 260's inherent accuracy)

QuickLOAD matches the measured ballistics within 7fps for each and says that the "Amount of propellant burned" is 98.72 and 99.82 respectively. A slight muzzle flash in evening shooting confirms this.

TrailBoss loads for plinking can be super short range accurate and is of course 100% burn.

In the name of continual improvement so please no "if it works, shoot it" comments because that is a given.

Questions:

What is the effect of percentage of powder burned in the barrel?
Is more burned better?
Is complete burn better?

 

[ksthomas]

jfseaman,

Just an aside here, but worth mentioning; the muzzle flash is not an indication of whether the powder is completely burned or not. You can still have very noticable (even bright) muzzle flash even when the powder is copletely consumed inside the barrel. The burning powder gases are themselves combustable, and when they get a sudden burst of fresh oxygen as teh bullet leaves the barrel, they can often reignite, causing muzzle flash. That's why most flash suppressors are designed the way they are; to break up the gases into smaller "clouds" that can't provide as large a flash as they would collectively without the suppressor.

 

[jfseaman]

Thanks Kevin,

I see that now. Physics is a wonderful thing.

Really surprised no one chimed in on this.

 

[DocB]

jfseaman,

98% and 98% are reasonable numbers. One gives room for boattail bullets to seat nicely without compression, and the other gives a reasonable amount of unburned powder, but the closer to 100% for % burned, the better. Think about how much powder is left with a 98% burn. Out of 50 grains, 1 grain is left unburned. Half a grain is usually worth about 25f/s, or a quarter MOA with most .308 bullets at 1k. Reducing the amount of unburned powder will usually reduce your ES.

HTH,
DocB

 

[Sniper Uncle]

jfseaman,

98% and 98% are reasonable numbers. One gives room for boattail bullets to seat nicely without compression, and the other gives a reasonable amount of unburned powder, but the closer to 100% for % burned, the better. Think about how much powder is left with a 98% burn. Out of 50 grains, 1 grain is left unburned. Half a grain is usually worth about 25f/s, or a quarter MOA with most .308 bullets at 1k. Reducing the amount of unburned powder will usually reduce your ES.

HTH,
DocB

Good point, Doc, never really thought about the ES ramifications. I'll have to recheck some of my loads on Quick Load to see the burned powder ratios again.