I think Savage actions have been greatly overlooked in this thread. When the thread started I wouldn't have expected people to have takent notice of what Savage is doing. But by now it should be obvious that they are producing some of the best actions in the world and putting them on their stock rifles. The people at 6mmbr
list the Savage Precision Target Action as one of the best "custom" actions in the world even though it is most often sold on stock rifles. I would think that any action listed as one of the best custom actions being sold (they do sell them alone without the rest of a rifle) would certainly rate as one of the best factory actions on the market. These Savage actions are incredibly stiff and strong. Even their heavy barrels have no problem remaining in position on these actions. There's a whole lot of people who have recognized the quality of these actions in the past couple of years. I'd suggest taking a look at the video on this web page
although it isn't quite up to date. There have been quite a few events dominated by Savage since this video was produced. And this action also appears on some varmint guns made by Savage. I have one on a 12 LRPV, single shot with a left port, right bolt setup. It has a 26" barrel and it is very stiff from one end to the other. I'm not a particularly good shot but I can shoot a 3" group at a quarter of a mile with my LRPV. Considering I have only shot that distance a few times in my life prior to picking up this Savage I'd say the rifle is doing a lot to make me look like a better shooter than I am. I've only had this gun to the range less than 10 times. If I could get in some more range time and if I could pick up some equipment to start loading my own ammo instead of using off the shelf stuff I'd say I could get even more accuracy from this rifle.
I don't doubt there are other quality actions available but I think Savage not only should have been mentioned here but I also think Savage leads the field in factory actions. The number of records and competition wins in the last 2 years would seem to back that up. Whether the army uses their rifles as the basis for sniper rifles or whether people ask for custom builds based on their actions has little to do with who makes the best action IMO. I see lots of people requesting lots of things that are not as good as other things they could be buying. I may be new to medium range shooting but I've been shooting for 47 years and there are some things I do know pretty well. And the army is often very slow about changing their ways. The true measure of who makes the best action is the number and quality level of competitions won. And in that regard Savage is far ahead of the actions you have mentioned.
I'm not trying to put down what anyone is doing or their equipment choices. I'm just pointing out what is the clear leader in quality of construction.