Re: set triggers
I don't have one. May well be my next rifle. I am a big fan of both the caliber and the rifle. I can address the twist issue.
My bullet of choice would be Bergers 140vld. Berger recomends a 1 in 9 twist. Bc is .640. I don't think 2900 fps would be unreasonable. This would be very pleasant to shoot, and extremely effective on game. I wouldn't personally look at bigger bullets because the velocity falls too much. Frankly, this bullet / cartridge is about ideal.
Let me offer another option. CZ offers the 550 American in the 6.5X55 (swede) case. I own one of these rifles in 243win. It is one of my most liked and most accurate rifles. CZ also offers a set trigger. It is a standard feature and the rifle will come with it. CZ is using an 8.6 twist rate for the 6.5.
At first glance in a loading manual you will see loads for a 140 grain pill equall to or slightly less than loads for the 260. However, the 6.5 is a bigger case. The maximum pressure for the 6.5 is set in defference to the numerous older swedish mausers in circulation today. I'll stick my neck out here and say the 6.5 can easily and safely be loaded to noticably outperform the 260 in a new bolt action! Anyway, just another option. Can't go wrong iether way!