Guns-N-Rugers, You just hit on a couple of my favorite subjects .... lock time and trigger pull, as they relate to accuracy. Everyone understands trigger pull and want their triggers to have a light smooth pull. Very few shooters understand "lock time" and don't realize it's detrimental effects.
Let's start with the sear. The sear is actually made up of two parts ... the notch in the hammer and the extension on the trigger. If you look at the hammer notch and trigger extension under a microscope, you will see machine marks that are lines in the metal running across the mating surfaces, which is opposite the direction of movement. When you pull the trigger on a cocked gun, these two surfaces create considerable friction which you can feel and the lighter the trigger pull, the more you feel sear movement (called creep). If the machine marks were cut in the direction of movement, you would barely notice creep. Herein lies the first obstacle to a smooth trigger pull.
The trigger extension tip can be stoned in the direction of movement and buffed to a high polish. This will pretty much eliminate machine marks and minimize the feeling of movement. The hammer notch is a different story. It is a shallow notch that is very hard to access. The surface is so shallow that you can't smooth it in the direction of movement so about your only choice is to use a fine "stone" and reduce the machine marks as much as possible. This can result in disaster if you change the sear angle or take off too much metal. Because the hammer-to-trigger position is very critical, you may find the hammer reaches full cock well before the cylinder latches. Additionally, if the sear angle is changed, you can get "push off" where the hammer can be pushed forward or jarred to unlatch the sear without touching the trigger. Both conditions can be very dangerous. I would highly recommend the hammer notch work be left to a professional with the right tools.
The actual trigger pull weight is a product of three things ... sear smoothness (covered above), trigger spring tension, and hammer spring tension. Ruger uses a very strong trigger spring so you can replace it with a Wolff or Power Custom light spring without compromising function. You can also lift one leg of the factory trigger spring off the stud and reduce trigger tension considerably (called "poor boy trigger job"), however this is not recommended because it can create other problems.
Now for the hammer spring and some "lock time" stuff. Single action revolvers are the most difficult of all handguns to master marksmanship. The gun itself is quite accurate but it's the "human factor" related to lock time (also called post trigger pull) that contributes to inaccuracy. Lock time is the amount of time it takes for the hammer to fall and hit the firing pin once the sear is released by pulling the trigger. Here's some comparisons: a typical bolt action rifle has a lock time of 10-15 milliseconds (.010 to .015 seconds), S&W K-frame revolvers take about 39 milliseconds, a Ruger SA revolver takes a whopping 75 milliseconds. That's because the Ruger SA hammers are very heavy and have a long distance to travel. Weight delays hammer movement and the long throw takes more time to travel. During that 75 ms, your hand can move the muzzle well off the target without even knowing it. Palming the grip (shooting high), anticipating recoil (pulling the muzzle down and shooting low), or poor trigger finger placement (pulling the muzzle to the side), are all things that happen during lock time. The longer the lock time, the more opportunity you have to pull the muzzle off target.
Reducing the hammer spring tension is one of the worst things you can do for overall accuracy. Yes, it does reduce trigger pull but you pay dearly for it in lock time. The ratios are pretty close ... if you reduce the hammer spring tension from 23 lbs to 20 lbs, that would be a 13% reduction ... hardly noticeable in actual trigger pull but here's what it does to lock time. A 13% increase in lock time would make the already long 75 ms about 85 ms. A reduction from 23 to 17 lbs (26%) will increase lock time to almost 95 ms. In my opinion, the hammer spring is the worst place to reduce trigger pull.
You can see first hand the effects of lock time by a technique called skip loading (also called ball-and-dummy). Have a friend load your revolver with a mix of live rounds and spent cases. When you shoot a live round, it's nearly impossible for those lock time bad habits to show up. However, when you get a click on a dud chamber, the muzzle will likely do a swan dive and/or pull to the side. It's very typical for a right handed shooter to pull low left. That's because of poor trigger finger placement, grips that don't fit you, and anticipating recoil.
Grips are very important to accuracy. The standard factory "plow handle" grips seldom fit anyone very well. Buy a set of grips where you can dry fire with minimal muzzle movement. There's nothing wrong with using one set of grips to shoot with and another set for "show-and-tell.
So, there are three conditions to satisfy before you can expect good accuracy ... pre-trigger pull where you hold the gun steady and align the sights. Trigger pull where a crisp pull will prevent you from jerking, and post trigger pull where you need to hold the gun very still to keep it on target. Of the three, a light trigger pull has the least effect on actual accuracy. Creep can drive you nuts because you expect the gun to go bang instead of feeling raspy movement or false sear release. Proper fitting grips help you stay on target while your finger is pulling the trigger and during post trigger pull.
So in conclusion, if you want to optimize accuracy with your SA revolver, here's some tips: replace the trigger spring with a lighter one. Stone and buff the trigger extension half of the sear but don't mess with the hammer notch. Use the factory hammer spring. Get some grips that fit you so you can pull the trigger without moving the muzzle. Practice dry firing until you find the "sweet spot" for your trigger finger ... usually in the middle of your "finger print". Try skip loading and watch your muzzle for movement. Don't dwell on a light trigger pull but strive for a "crisp" pull.