right VRS left, and gain twist?

[6.5x53.5]

Why is it we prefer a right twist north of the equator and Aussies
prefer a left twist south? What is the functional concept of gain twist? First left twist I've run into on our local market is the LAR grizzly in 45 win mag.

[Catfish]

I`m not sure about the twist, but it might be based on the fact the the air around a high presure area move in a clock wise direction in the Northen hemispher and counter clock wise direction in the Southern, low presure areas are the oppsite. The little funnel in your bathtube will move clock wise in the Northen hamisper and counter clcok wise in the Southern. As for the gain twist it started long ago because it was easier to keep the bullet from slipping in the rifleing if it were started at a slower rate then increased after you had it spinning than to shuve it into a very fast twist befor itstarted to spin.

[6.5x53.5]

Thanks Catfish, I'm attempting to find out who the techs are on the site. I agree it has something to do with earth rotation in relation to the magnetic poles. As for gain twist that I would think would mutilate the bullet as it arrives into the tighter twist this must affect barrel pressure and motion in a completely different way than the accepted whipping motion. Another one was that cannon round that had 2 trunnion like protrusions that rode two groves down the barrel "Carivelli?" Well we got this far AIN"T gonna qubbile about that!
Again thanks for your input should have polled this one.
6.5x53.5 AKA Dan