TTAG Commentator Dyspeptic Gunsmith [not shown] writes:
OK, let’s clear up some misconceptions:
1. Very good accuracy in a 1911 would be a 2″- group at 25 yards from a rest. Exceptional accuracy for a semi-auto pistol is a five-shot group of 2″ at 50 yards. That’s what the S&W Model 52 used to be tested to achieve. The S&W 52 would also be expected to put “10 rounds in the 10″ at 50 yards, a target area of about 3.3”. The S&W Model 52 was the pistol of the USAMU for years in the 60’s and 70’s.
2. Pistol accuracy is measured from the pistol being held in a Ransom Rest. Not shooting offhand, not shooting off sandbags, not handing it to a champion bullseye shooter.
3. A full length guide rod on a 1911 is a “solution in search of a problem.” Yes, I know all the supposed benefits of a full length guide rod. Want to know how many springs I’ve seen kink with a standard guide? None. I’ve fixed a bunch of 1911 issues for customers, and never has even one customer come to me with an issue that would be fixed with a full length guide rod.
4. Once the CNC machine mills the parts to exacting tolerances (and might I say these tolerances can only be achieved with a machine,)…
This will come as news to many gunsmiths, especially those who are old enough to remember match pistols from the “BC” (Before CNC) era of gun production. I regularly fit up parts with nothing more than files, polishing paper, lapping compound, measurement tools, a smoke lamp and a granite reference plate to tolerances tighter than the typical CNC machine can achieve.
The TIR on most CNC spindles is 0.0002″, the typical repeatable positioning accuracy is 0.0002″, even if you can command the machine to 0.0001″. OK, if the manufacture is running a machine like a Kitamura MyCenter, now we’re talking a temperature-controlled machine that can position down to 78 millionths and repeat down to 39 millionths of an inch.
Hand fitting with a smoke lamp and abrasives can get you down to a tenth or less. It just takes time, and skilled time costs money.
5. Let’s talk about accuracy – what is accuracy?
Accuracy is repeatability. Lots of people conflate or confuse accuracy and precision. They’re two very different mathematical ideas.
Precision is how tightly you can describe a measurement or observation. In a gun, let’s say you have a 40X March benchrest scope on a hunting rifle. You take your rifle on to the range at 100 yards. You not only see your target card in glorious detail, you can see a fly taking a crap on your target. With a 40X magnification scope, you could probably see a .223 hole in a target at 300+ yards, if the conditions are OK (ie, low heat shimmer).
What you have here is a very high level of precision – you can resolve individual holes in the target, you can even see a fly land on your target at 100 yards. If we want a different example, let’s say you have a measurement instrument (eg, a set of digital calipers), and thanks to the magic of digital electronics, you might have precision down to 0.0001″.
Now let’s talk about accuracy. Accuracy is how well you can repeat your shots. With your hideously expensive, but very nice, March scope, let’s say you send a round downrange. You can see your hole at 100 yards from a .223 round without a spotting scope. Your oh-so-wonderful scope allows you to see exactly where you put your first shot.
Now you want to shoot for a group – so you lay the crosshairs over your first round’s hole. You send the next one downrange… and it lands to the right and slightly up by about 1.5″. You can see quite clearly the first hole in your target, and now you can see the second hole in the target.
How accurate is your rifle at this point? Not all that much. You send down four more rounds while laying the crosshairs on your first bullet’s hole. You look at the group – eh, about 2″ for the most extreme spread, center-to-center. That’s mediocre accuracy. But man oh man, you’ve got precision coming out your ears – accuracy, not as much.
Accuracy is how well you can repeat something. Let’s go back to the set of digital calipers – they resolve or have precision down to 0.0001″. What’s the accuracy of that measurement instrument? About the same as for any other set of calipers – +/- about 0.002″ – and order of magnitude worse than the precision.
Same deal with a gun – if it can’t lay the rounds in one on top of the other, even when you can see exactly where the bullets are going, you’ve got an inaccurate gun with great sights.
When I’m shooting my Anschuetz rifle with match ammo, at 50 feet, if I can’t put every bullet in the center ring on an indoor offhand target, it’s my fault, and never anything but my fault. The rifle, sights and ammo are of such accuracy, that there’s no excuse on my part – even tho I cannot see the center ring in the aperture sights at 50 feet.