As an aside just for a bit of info, the reason that some TC's set the hammer back with heavy hunting loads wasn't because of the coil spring design....the coil spring design is fine.
The reason was that in the early years of production, the coils springs were too weak.
TC fixed that problem by cutting into production a slightly larger diameter and stronger coil spring which solved that solved the problem. I'm sure there are thousands of the early style weaker springs still out there though.
The coil spring is a way to make a lock using unskilled labor. It has no other desirable feature.
One must understand what Forsythe in "The Sporting Rifle and its Projectiles" called "the heavy first lifting" of the hammer on a percussion gun to grasp the idea of hammers blowing off the nipple and how this was prevented or at least greatly reduced by the makers of percussion rifles designed to shoot 100-120 grains of powder and 45 caliber bullets around 550 grains in weight. The technology was developed in the 18th century and was widely used on the best quality flintlocks by the 1780s if not before.
A properly designed lock takes less pressure, a lot less in fact, to pull the hammer from 1/2 cock to full cock than to raise it off the nipple. Instead of feeling the mainspring "stack" it actually seems to do the opposite and seems to "unstack" as the lock is cocked. Its necessary to experience this to understand it. While many locks have this feature to some minor extent. Few are as dramatic as a really good design that is assembled properly.
This started in the flintlocks with the stirrup tumblers and even to some extent with the "plain" tumbler.
It allows far less pressure at the sear nose when at full cock making it easier to get a nice trigger pull. In flint guns the increasing pressure as the cock moves forward helps to maintain the cock speed as the flint scrapes the frizzen. By the time percussion systems were in use the internal lock work was already perfected. The heavy pressure with the cock "down" was a real plus for the percussion guns.
In percussion guns the significantly higher pressure at rest will maintain the seat on the nipple and prevent the hammer from being blown off the nipple and is extreme cases even damaging the lock or worse the shooter.
This requires the tumbler, stirrup and mainspring to be properly designed and the mainspring carefully placed to make this work. If the tumbler is not properly made or the mainspring is off in its placement the lock will still work. But not as it should. Many if not all available "stirrup" tumbler locks generally available today have to mainspring misplaced and thus the performance is generally a little or a lot "off".
Comparing a lock from a Rigby LR rifle of 1875 (or a Joe Manton Flintlock of 1810) to a modern coil spring lock is like trying to compare a Rolls Royce to a Yugo.
Dan