I break down accuracy into three areas:
1) Basic mechanical accuracy of the gun. If that's not right, bzzt, fix it, sell it or throw it in the nearest deep body of water. It's unusual this side of a Jennings or Rohm or something to see it REALLY bad. Some calibers are more accurate than others, and subsonics (bullets going less than 1,050fps) usually have an edge. Some *calibers* have a rep for mediocre accuracy...the 40S&W for one. It has a short shell that isn't stabilized all that well in the chamber, it's usually set up with supersonic bullets and for other reasons people don't fully understand, it generally doesn't shoot as tight as either the 9mm or 45ACP. It's not "terrible" but you don't usually see 'em in pro competition, for a reason. Shells that are "long for the caliber" combined with subsonic bullets tend to be very accurate: 22LR, 38Spl, 44Spl, 45LC are all good examples. You can also get accurate supersonic loads but then your best bet is a heavy slug and VERY supersonic, don't mess around with the sound barrier, blast on through with a 454Casull, 475Linebaugh, 500S&W or the like. The 357 can't "blast through" the sound barrier unless you run heavy hardcast loaded hot, and then you "sorta can", but you won't match the heavy big-bore supersonics from the 454 on up.
BUT, the differences we're talking about won't be noticed until you hit 50+ yards, for all practical matters.
2) Usable sights. The sights make an incredible difference. Now granted, I've gone basically gonzo in this direction
. One thing people don't think about is "sight glinting" - in other words, take a bunch of shooters, see where their rounds are going early in the day, check again in the afternoon. The glint depending on where the sun is hitting their sights can throw their point of impact off - even good shooters run into this. I've gone to the last possible insane crazy length to fight glint
.
My sights are based on the theories of Tim Sheehan at Goshen Enterprises - his real production sights are better than mine:
http://www.goshen-hexsite.com/index2.htm
3) "Natural pointability": in other words, say you have no access to sights, or have to shoot from the hip. Does the gun "line up correctly" with your hand/wrist/forearm? In this one area, I think the Colt SAA ergonomics of 1873 flat-out dominates, esp. if you tune the grip panel thickness, shape and hammer reach to your hands as I've done with my near-clone Ruger New Vaquero.
What does all this add up to?
Well I can give you an interesting perspective. I went shooting today. Had a *terrible* time...this was out in the desert outside of Tucson, went way out there, went down a side-road that turned into a real roller-coaster of a rocky mess, managed to crash my 450lb streetbike, ended up with a bruised knee, sore right wrist, AWOL rear brake pedal, trashed turn signal...just a lousy time. Finally got it back up and rolling, got to a shooting spot that was already crowded so I couldn't do draw-from-holster work, decided to just plink...had to do so at long range because I was sharing a spot with some rifle guys that liked to bump-fire, NO WAY was I walking downrange.
And despite how crappy things had gone, I was rolling tin cans reliably at 40+ yards. And when I missed, it wasn't by much and windage only.
It was actually a pretty good test in the end: could I make hits even feeling like crap, just starting to get dark, with a shooting hand I'd landed on and had a blood blister on the palm? Answer: yeah. Sure could. Headshot accuracy offhand from a Weaver hold at 25 yards, *easy*. Those sights aren't just insane homebrew, they're also dialed in exactly for elevation and windage for 135 to 140gr ammo, and I had 130gr milsurp 38Spl ball with me, close enough.
Yeah. It's a weird as hell daily CCW piece, but I can hit what I shoot at. Not as fast as I want yet, that'll come...but I've got the basics together.
Now...it's NOT common that you need pinpoint accuracy in a personal defense situation. Most are close-range and fast. "Hostage shots" are incredibly rare, having to plink at some lunatic partially behind cover not quite as rare but still not too common. Having to headshot or hip-drop an assailant wearing a vest is also rare as hell.
But it feels good knowing I can make that kind of shot if I had to.