Shockwave:
The fruit we call an "orange" was originally a "naranj" but linguistic patterning of "an naranj" eventually became "an orange" (suspected development, still hypothetical). This happened again probably because people were constantly saying things like, "In naught-6 we had a drought..." and the second 'n' was found superfluous, eventually giving "aught."
That's exactly what I was trying to say! After the 1900s, people who had lived in the 1900s (before 1910) would tell stories to the young'ens, which began with the line "Back in naught six [or naught five or...], ...", and over time, to the younger generations, who didn't refer to any of they decades which THEY had lived in with a "naught", didn't really how to spell this shorthand exactly since they didn't use it themselves, and they heard this orally/phonetically as "back in aught six", rather than "back in naught six", as you say, seemingly rendering 1 'N' out of two. The N on the end of in could't go away, but the N in naught could be eliminated easily. I suspect we are exactly right on this.
Now, think on this for a second, though.... really, the correct way to type this phrase out with numbers and symbols rather than words, should be:
.30-'6
NOT .30-'06 as we do, because the naught or aught stands for zero, in which case .30-'06 would really mean ".30-006, and we're not nearly close to year 19,006 YET! (though I wouldn't be surprised of some people are still shooting this cartridge 17,000 years into the future!)