Twist rates vs altitude?

[Chrisjan]

I hopefully did not miss read the following.

Brian gave an example with a .243 shooting 95gr VLDs. At 5500ft it had 25% more stabilization.

I am at the same altitude, will I benefit from using a 9tw instad of 8tw shooting 105 VLDs?

At present my Dasher with 10 twist is shooting 95VLDs super accurate and no loss in BC measured.

 

[Bryan Litz Ballistics]

The thing that stands to be improved by slowing down the twist is precision (grouping).

The mechanism thru which you'll see an improvement in this area has to do with imbalance of spinning things; spin it slower, and you'll see less dispersion from a given amount of imbalance.

Therefore, the degree to which you'll see an improvement by slowing down twist is proportional to how much imbalance is present in your bullet (and potentially misalignment, etc)

With the current state of the art, bullets are so well balanced that it's unlikely you'll see an improvement in precision by slowing down the twist by 1 inch per turn. The imbalance that's present is so small, that's it's not contributing much at all to the overall dispersion, so minimizing that already small effect would not yield a big difference.

In the 'bad ol days' of crooked chambers, imbalanced bullets, etc, you could see a marked improvement in precision by slowing down twist rates. I think this is one of those ways of thinking that's persisted in modern times, despite the original reasoning being far less relevant today.

-Bryan

 

[Berger.Fan222]

I would not think about altitude as a reason to use a slower twist rate on a build.

But I would think about altitude as an opportunity to use a heavier bullet in a slower twist rate that I already had.