Many variables. such as:
-Cylinder throat diameters and uniformity
-degree of "thread choke in barrel from mounting into the frame
-barrel's bore/groove dimension ( uniformity at different parts of the barrel)
- "taper of travel" ( my term). You want to put these all together and have the cylinder throats uniform with a diameter just big enough to let the bullet pass through it with good pressure seal. THEN, you want the frame side of the barrel's groove diameter to be essentialy throat size, but not smaller than the groove diamter of the muzzle end. Bad accuracy comes from squeezing the bullet down at the frame end of the barrel (thread choke), then have the reduced diameter bullet travel down a barrel with a larger groove diameter ( causes gas blow by and leading for reduced accuracy.

You want a slight "taper" of bullet diameter from throat to muzzle, as the bullets travels out of the revolver.

You want uniform cylinder throats, because it creates a uniform starting diameter for maximizing accuracy.

Case in point. I have a stainless Ruger GP100 ( 4" bbl) in 357 mag. With 170 grain Keith bullets (from Leadhead bullets, sized 0.358" ) I was getting 3-4" groups at 25 yards. Three shots were close, and three shots were much wider. I slugged the cylinder throats. 10.358" , 20.357" , 1 @0.356+ ", 20.355". I slugged the barrel from the muzzle, and detected increased resistance at the frame area ( thread choke).

I sent the cylinder to the "cylindersmith.com" to have the throats reamed to 0.358" (all are now uniform, and equal to the largest throat) . I then fire lapped the barrel to open up the thread choke constriction ( took about 50 shots total (~20 with 400 grit bullets, then 30 shots with 800 grit embedded bullets). Thread choke is gone, and a barrel slug passes easily without restriction/drag at the frame.

I shot the same 170 swc Keith Leadhead bullet load in the modified GP100 and got a nice round groups of 1.25" @ 25 yards. I haven't done much load testing to see if there is a "best accuracy" reload for this revolver, but I was happy with the results ( this all happened 18-20 years ago). I just haven't shot this Ruger that much; but, enough to enjoy it "as is". I was disappointed with the variable original throat diameters of my GP100. I'm satisfied with it now (also did a polish and trigger job on it to for a trigger which feels close to my S&W k38.

So, there multiple variables that contribute to ( or degrade) accuracy. All errors are additive. Eliminate them, and the process (accuracy in the case) improves. So, at what distance can a revolver generate a 3" group? Depends. It mat be 15-20 yards for some revolvers and loads, or 5O yards, or even 100 yards. I would like to mount a Wigatinny scope base and a pistol scope on my Ruger to find out what kind of accjracy potential it really has. I'd like to load it with wadcutters and go squirrel hunting with it.

A tuned and accurized 1911 45 acp for bullseye shooting should have x-ring accuracy at 50 yards, which is 1.5" ( 3 moa).

"Behavior accepted is behavior repeated."

"Strive to be underestimated."