Powder Burn Rates and Temp Sensitivity

[Brett]

Nice chart! I just printed it to add to my reloading info folder. Thanks

[PGW Steve]

Thanks for the repost, I haven't seen this till now!! Well this just showed I'm wasting my time with CFE 223. I live in Manitoba where winter temps are -35C and summer +35C.

[bj139]

This is a great chart.
Thanks, NF.

[Six5x39]

about the burn rate ... for 16" barrel , is it best to stick with fast burning powder ?

[RiverRider]

Homer Powley used to say that all the powder that was destined to burn would do so in the first few inches of bullet travel. I think that's been pretty much tossed out the window as of late, but in MY opinion you're still better off using the slower burning numbers. In general, the powder that gives you the highest velocity from a 26-inch barrel will also give you the highest velocity from a 9-inch barrel. I believe this is true for cartridges in the .30-06 class on down.

[lrgrendel]

So this thread got me thinking!

The published velocities and bullet drops are really worthless on the boxes of factory ammo?
Maybe for 100/200 yd shots it’s ok but someone shooting any longer say at +110F or -30F the info would be so inaccurate it would not be worth using?

Unless all factory powders are really temperature sensitive.....

[NugginFutz]

The drop #'s printed on some boxes of rifle ammunition are based on a given barrel, at standard pressure and temperature. Go to sea level, with the 22 or 24" barrel, shoot at 69'F and your results should be very close to those on said box flap.

As a rule, the match and hunting ammo has to be relatively stable, or customers would be complaining and sales would suffer. I've not heard any ammunition manufacturers specifically state what their #'s might be, but many do claim stability as one of the reasons to go with their products. Hornady claims "...
Having said that, it's a fair bet that the best powders will show some variance if shot at the extremes you mention, Likewise, shooting at 14,000' ASL is going to give you phenomenal performance, as opposed to sea level. It's all a matter of managing your expectations and understanding the limitations of the product.

As for my own loads, I don't have a single dope card for my most reliable, stable load of Varget or 8208 that I can use anywhere. It just isn't possible.

Hope this helps.

[Sticks]

about the burn rate ... for 16" barrel , is it best to stick with fast burning powder ?

Homer Powley used to say that all the powder that was destined to burn would do so in the first few inches of bullet travel. I think that's been pretty much tossed out the window as of late, but in MY opinion you're still better off using the slower burning numbers. In general, the powder that gives you the highest velocity from a 26-inch barrel will also give you the highest velocity from a 9-inch barrel. I believe this is true for cartridges in the .30-06 class on down.

Short answer - No. Faster powder in a shorter barrel does equate to best option.

I did all manner of reading up on that and that was the general consensus. One article did some testing with all things being equal, two barrels (one long, one short) two powders (opposite ends of the burn rate chart). Both barrels actually got better performance out of the slower burning powder. IIRG is was 5.56 that they were testing on.

So why is there fast rifle powder?....Everything has it's application. Barrel length is not part of it.

Having said that - IIRC StoneHendge noted that with some of the powders that he was using, the heat zones in the barrel changed. Some were hot at the chamber, others were hot at the muzzle. I am not sure where the ideal "hot spot" would be. Logic says equal temps all the way down the pipe, but my math and science ended at the 9th grade level.

[RiverRider]

It might be worth pointing out that there might be reasons to choose a little bit faster burning powder, and I can think of two: one would be muzzle flash considerations, and the other would be port pressure considerations in gas-operated semiautos.

By and large, case capacity, bore diameter, and bullet sectional density dictate proper powder application.

[LRRPF52]

So this thread got me thinking!

The published velocities and bullet drops are really worthless on the boxes of factory ammo?
Maybe for 100/200 yd shots it’s ok but someone shooting any longer say at +110F or -30F the info would be so inaccurate it would not be worth using?

Unless all factory powders are really temperature sensitive.....

Within 300yds, you're looking at maybe an inch or two in most cases.

[mdewitt71]

Cool chart, found on a Google search and it brought me back here.
Figured I'd bump to share in case others had not seen it.