Everything Seems Obvious in Hindsight
Note: I am not an expert on societal-technological changes and I invite comments from anyone with more information on the following generalizations I have made. What I have written was on the basis of a conversation with my great-uncle, who was born around the turn of the (20th) century. I asked him what was the greatest invention in his lifetime, thinking he would say the airplane, or going to the moon, or maybe the Internet (in its early days at the time). But he told me the single thing that changed everything was the car. - KJT
Brakes and Other Inventions Only Obvious in Hindsight
Today standardization of parts and assembly lines are taken for granted. It's hard to remember how obvious these things weren't a hundred years ago. Other things that are obvious now that weren't then are parachutes, landing traffic patterns, and brakes. (And that mixing large groups of people around all over the world is a great way to spread flu...more on that very soon!)
When you think about it, before railroads (1830s), automobiles (1880s, or 1908 for the common man), and paved roads (late 1800s), cutting down on speed was not a major problem, and mostly it would involve cutting your horsepower by slowing down your horse. In 1918, there had been a revolution in transportation in living memory. Many people in rural areas (and most of America was rural) were still essentially living in the time before the transportation revolution, and would for decades to come. Details of how to use the transportation such as seatbelts, traffic routing, and four-wheel brakes (a project of Eddie Rickenbacker's after the war) were still being worked out.
When Craftsmanship Was Everything
Like brakes, standardizing parts for equipment a variety of people would need to use, such as guns, seems obvious now. But at a time when most people grew up on farms, shipping was expensive, and few people traveled far in an entire lifetime, things would be made locally if possible and fit to the situation.
Some people had hilly land, some had a farm by a creek, some had an orchard, others raised tobacco. If five farms in the area had a similar landscape and product, was it worth it to make something standardized that was not quite perfect for any of them but fairly useful for all of them? Maybe - and maybe not. War and emergencies were a strong motivator for standardized systems (for example, railroad gauges in the Civil War and fire hydrants in a 1904 Baltimore fire) but those don't happen every day.
Cars Changed Everything
With the invention of the automobile, people were suddenly traveling further away, and costs of shipping products dropped while speed of shipping rose. Even without the Great War, better transportation was opening up more opportunities for standardization, and better standardization (remember the Model T) also improved transportation, in a "virtuous circle".
As the Internet puts the Great War Stories Gift Shop in touch with the 0.001% of people who have a need for plastic World War I helmets to wear in a parade or a reenactment or a diorama (or who just like the doughboy style), the transportation revolution allowed cheese produced in Littleton, Colorado, to be sold from Wyoming to New Mexico, thus standardizing the customer experience, to borrow a very anachronistic phrase.
Rickenbacker Was A Forward Thinker
All this is background to explain why Eddie Rickenbacker's ideas about guns today receive a, "well yeah, of course!" reaction but were radical ideas at the time (though not unique to Rickenbacker; Guynemer and Lufbery, for instance, were also known for meticulous attention to detail in the state of their guns.)
Rickenbacker worked out several ideas with Abe, his teen-aged mechanic who "quickly caught on to some of my antidotes for the jamming of the guns," according to Rickenbacker's autobiography.
One of the faults lay in the ammunition. Shell cases were not uniform in size and would stick in the chamber. Abe made a template calibrated to the exact size of the shell, and from then on each shell was tested and, if faulty, discarded.
In low temperatures at high altitudes, the lubricating oil in the guns became heavy. It would stick in any rough spot on any sliding part of the gun mechanism. I obtained a little sharpening stone, and from then on you would usually find me with a gun part in one hand and a stone in the other, honing it smooth.
Suppose the guns still jammed? I remembered the copper-headed hammer of my racing days. Abe worked a leather thong through the handle of one so that it could be fastened to my right wrist and be always available. A sharp blow with it cleared many a jam.