Re: Variable barrel twist.
Don't know much about the "advantages" of gain-twist barrels, but they seem to come back around every couple of decades. I am in possession of my grandfathers custom .270 Win. built in the early 1960's. Back then, the popularity of an outdoors writer by the name of Jack O'Connor was on the rise. Jack was in love with the .270 and was shooting everything on all continents to prove it was a do-all caliber. Grandpa just had to have one.
His rifle was built on a model 98 Mauser action brought back from Europe after WW II (the action still has a German swastika on it). It wears a a custom .270 Win. barrel with a gain-twist from 1:12 to 1:10. Supposedly, it made the bullets shoot "flatter". Although he never could adequately explain what the advantage was to my satisfaction, there was a lot of mystic surrounding the rifle and it was the envy of every hunter in camp. I haven't shot it in 30+ years as I value the rifle more as a great example of a by-gone era.