I think my way is the proper and most respected way.
Sir, you can think that if you wish, but it's not correct. If it were, we'd write "an radar scope." ("Radar" is a an abbreviation of "radio detection and ranging.")
The general rule about "a" and "an" with abbreviations is to base the article on how the abbreviation, not the full phrase, is pronounced in speech. If the abbreviation starts with a consonant sound, then it gets the article "a," as in, "
a Federal Communications Commission ruling" (starts with a "fed" sound). If the abbreviation starts with a vowel sound, it gets the article "an," as in, "
an FCC ruling" (starts with an "eff" sound). As in these examples, sometimes the abbreviation takes a different article than the full expression does; this happens with some frequency.
So anyway, "S&W," because it starts with a vowel sound ("ess"), properly takes the article "an," as in "an S&W revolver is ...."
Hope this helps, and Semper Fi.
Ron H.