After 45 years with the 1911, and 35 gunsmithing here's what I've learned about why some 1911's aren't reliable:
As above, many makers who don't follow Colt/USGI standards and specs.
The old Colt's and GI guns were made by slavishly following Colt standards and specs. The guns always worked great.
New makers follow whatever standards and specs they feel like, and change for any reason or no reason.
The older guns were made of solid forged and milled steel.
Todays guns are often castings, with heavy use of MIM and stamped parts, with a good mix of aluminum and plastic thrown in.
The original Colt was "old technology" and newer makers are trying to build it with "new technology" often with mixed results.
Too many people insist on thinking that ANY ammo should work in ANY gun.
They decide they'll use a specific brand/type and resist trying something else even when the gun doesn't "like" the ammo.
Much of this is the fault of the "what's the BEST ammo" question.
In truth, most all American Premium defense ammo is pretty well equal in performance.
Pick one that's PROVEN to work in YOUR gun.
Too many people insist on spending big bucks on the gun, agonize over what's the best lube, spend big bucks on the "Right" holster, buy only the finest custom grips.....Then shoot Ivan's "$2.50 per 100 rounds" of the cheapest ammo possible.
After doing so, they then proceed to clean the gun with God knows what "expedient" chemicals and equipment.
For some reason, they seem to think that some home-made chemical concoction and a ball of steel wool is just as good as chemicals and equipment specifically developed for cleaning guns WITHOUT damaging them.
They never see the "Penny wise, Dollar foolish" part of having a gun costing hundreds or even thousands of dollars, and trying to save a few cents on cleaning gear.
To what end?
Playing with the springs.
This is my #ONE cause for problems.
John Browning, Colt, and the US government spent millions of dollars, and nearly 100 years developing the 1911 and refining it to near perfection.
For some reason yet unexplained, a new shooter with his first ever handgun seems to think he's qualified to decide that Browning and Colt were WRONG, and that a different spring will work better.
Some people have a problem and simply decide that instead of properly diagnosing and fixing the problem, they'll just replace the springs.
Sometimes this gets the gun working, but since the real problem wasn't fixed, the gun is unreliable.
This has reached the point where a customer with a 1911 that was leading up with cheap soft lead reloads actually asked me if a stronger recoil spring would "fix" that.
To paraphrase Congressman Fritz Hollings "There's too much of that springin' goin' on out there".
Alterations to the gun.
EVERYBODY thinks he's a pistolsmith. They have no problem taking a file, stone, or the dreaded Dremel to a perfectly reliable 1911, to "improve reliability".
What they usually do is Dis-improve reliability.
Too many people have a "I can do that" attitude and start altering parts with NO real understanding of how they function and interrelate with the gun as a whole.
After this many years I can tell MANY stories of some of the unbelievable things people have done to "improve" perfectly good guns.
Misunderstanding gunsmith's terms:
My favorite is "polishing" feed ramps and parts.
When a gunsmith speaks of "Polishing" parts, we REALLY mean smoothing or deburring.
Bringing parts or feed ramps to a mirror shine contributes NOTHING.
What we want is a slick, smooth part or ramp that won't catch or drag working parts or bullets.
Too many people hear "polish" and think "Like a mirror".
In pursuit of the mirror shine they take too much metal off and alter dimensions.
All that's needed, is SMOOTH, not shiny.
Why do pistolsmith's polish parts to a mirror shine?
Because the customers demand it. Do a smoothing job on the feed ramp, and the customer thinks you either forgot to do it, or you're trying to rip him off.
If it's not mirror bright, it just wasn't done, was it?
Tighter fit:
The most reliable 1911's were the GI spec "loose as a goose" guns.
Looser fit, means less possibility of dirt, ammo problems, or lack of lube causing a stoppage.
The problem is, customers don't really know what they want.
They demand an accurate gun, and bitterly complain when it won't shoot tight groups.
The makers tighten up specs to improve accuracy, which degrades reliability.
The customers then bitterly complain that the gun jams.
Decide what you want.
Do you want a target pistol or a combat pistol?
A target pistol is built for maximum accuracy at ALL COST. Reliability is sacrificed for accuracy.
A combat pistol has to, AT BEST, hit a man in the chest at 50 yards. You aren't going to be able to pick which eye you hit in a real gunfight, and ALL that counts is that the gun go "BANG" when you need it.
One trainer says that a real combat pistol needs accuracy of "About 6 inches at 6 feet".
A 1911 that attempts to compromise between good accuracy and good reliability is often neither.
Accessorization:
We all have an urge to make a personal weapon "Ours" by making it unlike all the other guns out there.
To this end, people are guilty of adding parts and accessories that not only don't add any real functionality, they often degrade it.
Before adding ANYTHING to a real defense gun, do a "real world" cost-benefit analysis: "If I add this, what EXACTLY do I gain, other than appearance"? "What do I loose in real functionality and simplicity"?
In other words, do you want a Hollywood Range Toy, or do you want a People Shooter?
The very latest "Oh, COOL. Current Fad addition".
In the 60's EVERY "with it" 1911 owner just HAD to have S&W sights complete with a front sight so long and big it looked like a fin off a 50's car, and the most radical hooked trigger guard possible.
Today, it's odd-ball sights, radically up-curved grip safeties, guide rods, and titanium parts.
The 1911 works best when it meets the following standards:
Simple Is Better.
K.I.S.S.=Keep It Simple, Stupid.
Less Is More.
Most of the current fads will pass, just like the ones that were popular years ago, and will be replaced by new fads. Most of which add NOTHING to reliability, and usually put it at risk.
Failure to break in:
Too many people take a new 1911 out of the box, fire 20 rounds through it and have problems.
Enraged at getting a lemon, they bitterly complain, and often dump the gun.
Break the gun in. A typical 1911 is starting to break in after about 200 rounds.
Failure to verify reliability:
MOST people buy a new gun, and never give it a reliability verification.
To verify the reliability of a defense gun:
Thoroughly clean and properly lube the gun .
Take GOOD magazines, (also cleaned) and your chosen defense ammo to the range.
Shoot 100 to 200 rounds, whichever you feel comfortable with in ONE session. If you can't shoot it all in one session don't clean, disassemble or do ANYTHING to the gun.
If the gun will shoot the entire 100 to 200 rounds with NO=ZERO stoppages, THAT gun is reliable with THAT ammo, and THOSE magazines.
Change ANYTHING and the entire package needs to be re-verified.
Bottom Line: If you want a reliable 1911, buy the closest thing to an original Colt-GI gun, from a top maker.
KEEP it as close to unaltered as you can.
If you want something that looks nice or Cool, buy another gun to use as a toy.
DON'T screw with it. If it isn't working let a REAL pro fix it so it does.
Don't change ANYTHING unless there's a verified need to do so.