Case fill and burn %

[Huntaddict]

I took a look at some testing that was done in recent areas of temp variations. I wanted to know

Many brands claim that their powders are not temp sensitive, across certain types. Not all but most of the newer powders do carry that marketing around them. I wanted to see what NATO testing found with modern powders.

Cliff notes - in the graph they did find variations on velocities depending on powder, in this case Varget and TAC were tested. Varget is famous for being very temp stable.

Testing was conducted from -65 degrees to 140 degrees. I would venture that <1% of hunters are hunting in those conditions in the same year. Note: In "normal" hunting temps with Varget, -10 and 90 degrees Fahrenheit, the found approx a 15fps variance in velocity. Tac saw a more

Does this mean you have to change powder in your rifle? I have never been on a hunt or shoot where temps have changed that much in a day or two. Up to you.

However to me, I am zeroing my rifle at every hunt so unless I am seeing pressure signs hunting in 90+ degree temps, I am going to rezero, validate and go without ever changing my powder. Why i try to stay in the 90-94% range, to ensure I have my most accurate node without issue...at any temp.

 

[huntsd123]

newb reloader here. How do you tell your %? is it just off a manual for max load?

 

[Buttermilk]

I like to be 90+ % on case fill. I couldn't care less about burn %.

I shoot a lot of short barrel guns and have for 40 plus years. I've never had an accuracy problem with slow burning powders, and short barrels.

 

[Justice1327]

I pay absolutely no attention to case fill percentage, because it's a meaningless measurement outside of compressed loads. Using Lee's 1-Graon calc factor, I've significantly downloaded almost everything in the 30-06 case family, and my 264 WM.
My 204 is the daily shooting warhorse against vermin arrive the ranch. It's most accurate load is a fair amount below the Hodgy starting load. But the burning curve is stable.

Case fill percentage is not meaningless. You get a flash over your powder and you will see what I mean.

 

[FEENIX]

newb reloader here. How do you tell your %? is it just off a manual for max load?

I provided an example in #10 (a QL product). If you use QL or GRT, the software can project that.

 

[RegionRat]

newb reloader here. How do you tell your %? is it just off a manual for max load?

The popular internal ballistics models like Gordon's and QuickLoad give them as part of the output.

The case volume is based on the standards or user input. The powder volume is based on the density. The bullet geometry is known and with the seating depth, we can calculate how much internal case volume is left over.

Some manuals also list it.

Here is a screenshot example from Gordon's where I'll point to the case fill which they call load ratio. Just below it, is the percent burned estimate.

 

[M1A1ABRAMS]

newb reloader here. How do you tell your %? is it just off a manual for max load?

I suggest get yourself a reloading manual (S). And read it carefully. Don't rely on the internet for everything.

 

[twocan]

I was always taught 90% case fill. I see my best results with 90% or more.

I agree, but my best loads are at 95% for .338 Lapua Mag and .30-06 Springfield.