Powder burn rates and rifle twist

[PaLuke]

Hopefully I word this right. Is there any testing that shows certain barrel twist prefer certain burn rate powders. Meaning does a 1:10 twist 7mm mag prefer powders in the slower rate compared to a 1:8 twist preferring faster burn rate powders or just opposite? I know each rifle is different but was curious to your findings. Thank you for your replies and time.

 

[RockyMtnMT]

I am not sure that it makes enough difference in the pressure to see a different powder consistently work better in the varying twist. You are probably only talking 30fps change due to twist. Other variables such as bore tolerance will probably make a bigger difference. Or even lot to lot powder changes.

My .02

Steve

 

[PaLuke]

Thanks for the reply. I'm sure you are 100% right. Just thinking outside the box. Thanks again

 

[RockyMtnMT]

Thanks for the reply. I'm sure you are 100% right. Just thinking outside the box. Thanks again

Lol I am glad you are confident that I am right. I am not always so confident. Seems like every rifle is a new learning experience that pushes what I thought I knew. It keeps it fun.

Steve

 

[Kevin Rohrer]

The bullet weight to caliber ratio determines the proper twist rate; heavier bullets (i.e. longer) for a caliber dictate a faster twist.

The size of the case determines the powder speed; larger cases work better w/ slower powders because they fill-up the case more and tend to give lower pressures for different velocities.

You buy a rifle w/ a twist rate based on the bullet weight-range you will use in it, and pick a range of powders to try based on what reloading manuals say are appropriate for the case-size if loading full-power loads.

 

[Mikecr]

Is there any testing that shows certain barrel twist prefer certain burn rate powders.

There could be. It would take a lot of research to find evidence of it out there, and chances are it wouldn't apply directly to YOUR cartridge, barrel, bullet combination.
Even QuickLoad doesn't account for this.

I believe that twist rate would affect pressure peak amplitude and location. That a slower powder would be in order for a faster twist, to mitigate early pressure problems.
It's a good thing we have a range of powder speeds for any given capacity/bullet. A poll would show that the full range is used, for each of us to arrive at accuracy with different powder.
Trial & error

 

[Mikecr]

Maybe you could dig in and find anecdotal evidence here:
The Rifle Section @ www.reloadersnest.com

 

[MagnumManiac]

I asked this very question to a ballistician at Nolser and he stated that twist rate has no affect on either max pressure or velocity, they used the same loaded rounds (5.56 NATO) in twists from 1:7: to 1:12" with no difference whatsoever.
Even using bullets that are typically used in 1:14" twists had the same velocity in the faster twist barrels.
As to a preference in burn rate, I can't really see there being a difference, unless someone can come up with some evidence to prove otherwise.

Cheers.
gun)

 

[Edd]

Bryan Litz did a test on velocity change with twist rate. He found the average velocity difference between the different twist rates was less than the velocity difference between shots fired from the same barrel.

 

[Mikecr]

Surprising to me. Excellent info guys