all created equally?

[smokey240sx]

I constantly finding myself doing research on reliability of firearms. Maybe its because of my lack of understanding about the firearm manufacturing process. To my understanding everything are machined and molded. So why would one guy have a perfect shooting firearm yet another can't even get pass the first mag? I'm not tring to sound like a smart ass but I am curious.

[ar15jules]

While I am not an engineer or machinist, I would be willing to bet that guns that A: are engineered better to begin with are superior, and B: guns that are made to strict tolerances are better. I don't mean that every 1911 needs to lock up tighter than all get out, but the manufacturing process is more strict, turning out a more consistant part.... Use a car analogy. Why can they grab several hundred more horse power and rev and F1 car to beyond fifteen thousand RPM's compared to the one you buy at your local dealer? Engineering and machining tolerances.
Jules

[smokey240sx]

Maybe I'm giving them to much credit but if you got a perfect well calculated proto the just mass produce them. I can't believe the engineers saying "thats good enough, let crank this out". Could it be that the mold gets warped after while?

[unclesam099]

It's because there is variation in every process. There is no such thing as ZERO defects. Statistically, you can only approach zero but never reach it. There are just too many variables.

[Rosko Packer]

Don't forget that in this whole set of processes to get from raw materials to finished product there can be any number of quality control checks. They are expensive (especially with the companys that scrap or "move to start" those that don't pass). The level that says "Good enough" can be a very high or pretty low one. If the design and engineering are good, a company can produce a high percentage of good product (especially with modern CNC and other machining). It is still the QC checks and the level of perfection a company is willing to pay for that can make a big difference. You can still get a lemon almost anywhere and at almost any price, unless you are dealing with the top-most, hand crafted and fitted items.

[mjfletcher]

as someone else mentioned, tolerances come into play. one manufacturer might allow 3 thousands of an inch (.003) in variation and another might allow 6 thousands of an inch (.006) and both would consider that acceptable tolerances. But if every piece that goes into one of the guns is off by the maximum tolerance, some plus some minus, It could result in a gun that jams heavily or has other problems.

Two guns coming off the line back to back can have pieces and parts that are closer and further from perfect but still within acceptable tolerance so pass all QC checks but result in one gun firing flawlessly and the other being an expensive paperweight.

ie: Firing pin is .006 inch shorter than spec, breech face is .006 inches thicker than spec, chamber is .006 inches shorter than spec. result is .012 inch less of the firing pin passes thru the breechface to strike the primer and the cartridge is .006 inches further forward than spec so the indentation in the primer is .018 inches shallower than the prototypes design. That MAY be enough to result in regular soft hits on the primer and failure to fire depending on the tolerances of other surrounding parts.

[VeryPrivate]

Reliability is a difficult subject to discuss. Whole textbooks on the subject do not do it justice. The history of the M-16 rifle is an interesting case study. There were a number of technical issues to overcome but also politics and prejudice.
For example:
The original furniture was made of Bakelite. This type of plastic was very brittle and broke easily.
The original barrel was not Chrome-lined and corroded more readily.
The original .223 cartridge used a stick power, but service ammunition used a ball powder the left a heavy residue in the barrel and gas tube.
The original firing pin was too heavy and caused slam-fires.
And my favorite:
During cold weather testing in AK, accuracy results were poor. Armalite discovered that the front sights had been removed and replaced with welding wire. The CO of the base was sabotaging the test to stop the Army from adopting a .223 caliber rifle.

In my own experience, I replaced the mainspring on my P220 to try and lighten the trigger pull. It promptly rendered the pistol inoperable. Hammer fell, but the firing pin did not hit the primer hard enough to ignite it. The original mainspring was reinstalled that afternoon.

On the practical side, there is no scientific way to compare the reliability of one firearm to another with the data provided to the general public. You have to go with manufacturers reputation and a hands-on inspection of the comparison samples.

As a side note, do not trust the firearms media. After years of reading these articles, I discovered a pattern of "X shoots great...fits hand...excellent...I like this brand of sight...this rest...the range owner is an old friend of mine..." Never criticism of the pistol/rifle (all of which are provided by the manufacturer) or anything negative about the product. They must be all perfect. The media depend upon advertisers, who are of course the manufacturers. As such, the articles are slanted to show the good points and not necessarily any negatives. One author even wrote in his book, that when he had trouble with a specimen he returned it and would not publish anything until that delivered an improved specimen. To me this is a disservice. I want to know who the crappy manufactures are.

[TaePo]

If you want to know a little bit more about workholding and accuracy/tolerances...

I used to work for this company and we had some major gun mfgers as our customers:

http://www.chick-workholding.com/

I do not know if they still have videos available on the site or some animations. Overall, quite a clever design, and the more you look into how they work the more interesting the features.

[Jup06]

I think Mjfletcher hit the nail on the head. As far as tolerances, you come to a point where each mil of precision becomes so expensive, nobody would buy the firearm. So quality control and inspection are really the only things that assure a decent weapon is leaving the factory.

There have always been guys that simply will not keep a 1911 factory stock. They get the edges smoothed, trigger jobs etc. Yet, this has not prompted Colt to break their edges. The STI models have a nicer fit and finish, but I'll stick with Colt.

One of my buddies friends recently came back from a gun show with a new Bersa semi-auto. I looked at and tried not to make a face becuase I didn't want to hurt his feelings. About 2 months later when I heard he had to send it back to the factory, I was not suprised. For the most part, I think you get what you pay for.

What I find interesting is manufacturers who purposely make their products so they fail after a certain time period, guaranteeing repeat customers. These days, most consumer products seem to have a hint of this.

[Nic]

I just watched a video of the inner workings of a Smith and Wesson plant. A worker took a red hot piece of steel, that was on the end of a very long pole, and placed it into a one sided mold. A HUGE press slammed down on it, then the worker took the hot steel and physically moved it to the second mold, and the press slammed down on it again. Lastly, the worker moved the same piece of hot steel and turned it upside down and placed it into the third and last mold. The press slammed it for the third and last time. The hot steel never left the end of the pole. The process was very quick. As I watched this, I couldn't help but wonder why they were doing this by hand... if the worker moved it or placed it into the mold at the wrong angle with the very long pole, it would seem that the final outcome would not exactly be precise. Could be one reason why there are differences in like models. Nic