Rabbit Holes.
Okay folks, here's my input after folks are running deeply down rabbit holes.
Single versus set triggers are mainly down to personal preference, with some advantages to each.
Let's back up to 50,000 feet and be realistic. What is the biggest influence on accuracy? The monkey on the crank. The shooter. Unless you are shooting your gun clamped in some machine rest, the shooter normally has the biggest influence on accuracy, especially offhand.
Mechanical accuracy is how the gun shoots clamped in a bench vise of some sort. PRACTICAL accuracy is how "shootable" the gun is when combined with the shooter.
If you clamp a pistol in a machine rest, and it shoots a 1/2" group at 50 yards, that is great mechanical accuracy. Let's say that same pistol has a 12-pound trigger. Offhand, even an Olympic grade shooter would be challenged to hit the target offhand. So, this would demonstrate poor practical accuracy. Same gun. Why am I referring to pistols? Because they are harder to shoot accurately than a rifle for the same shooter. Same applies to rifles though.
Practical accuracy is how the gun works with the shooter to get a shot on target. Breaking the trigger without moving the sights off target. I personally believe that a set trigger allows for more practical accuracy for the normal shooter. It helps minimize or eliminate the possibility of a shooter "yanking" a trigger, and pulling the gun off target. I personally despise a heavy trigger. A gun with a heavy trigger either doesn't get shot or goes back for work to reduce the pull weight and improve the break.
Yes, I have shot a ton of single triggers in my life on all sorts of guns. Some were excellent, some were appalling. I still can shoot a set trigger better. Especially offhand. For me, a set trigger minimizes the time between when I initiate my trigger press and when the gun completes a surprise break. Little to no creep as well.
When discussing the set trigger "jarring" the gun before ignition, I think "really??" With that huge cock whacking a frizzen someone thinks the "jarring" of a set trigger makes any practical difference?
My belief is that the practical benefits to a shooter of a set trigger minimizing yanking-off-target far outweigh the small theoretical advantages of single triggers. Unless you are talking hunting, especially in cold weather.
Think back to the long range matches at Creed's Moor on Long Island in the 19th century. They put a weight limit on guns (to separate the men from boys on recoil), and they specified single triggers (to separate the men from boys on trigger break). They must have felt set triggers were an advantage?
For hunting in cold weather? I can see a good single trigger could be a smart choice. A double lever set trigger can also work in that climate.....just don't set the rear trigger. Run it as a single trigger. I personally am a bit nervous about Appalachian set triggers where the trigger has to be set before the lock can be cocked. Especially for hunting.
One big negative for me is that many makers (past and present) don't know how to install a single trigger and set up a lock with a light pull. There are many out there with heavy, balky triggers, and that isn't so easy to correct as with modern firearms. There are makers who understand triggers and make great trigger pulls, I will readily admit.
Since my guns get shot versus hanging on a wall, I tend to have established opinions about barrels, locks, and triggers. Please forgive me if I have offended anyone. That was not my intent.
Just keep in mind theoretical and mechanical accuracy versus practical accuracy.
Enough of my thoughts for now.
God Bless, Marc