i believe the best compromise for the 40g would be 1 in 11, i believe border barrels are now making a barrel for the .204, and have built a few rifles to find a good twist rate..
i was surprised to see the sako not being the most accurate for a change, and also had problems extracting the round at times...
As you also state the twist could be marginally either side of the 1 in 12, hence leading to one gun shooting the 40's and the same make not liking them at all.
it's a cracking round to shoot, and when a load is developed extremely accurate outta the box.....
looking forwar