The problem with pedantry is it can be tripped.
Consider the Garand. You insert the en bloc clip into the (fixed) magazine. When the last bullet was fired the clip is ejected.
SOME clips - most of them today - are loading clips aka stripper clips. But some clips such as the en bloc clip behave remarkably like detachable magazines.
Second point. Languages change. English is particularly bad about this. Words get borrowed. Their meaning changes. (Awful used to mean awe-inspiring, not terrible.) The changes can happen in less than a decade. (Bad took about five years to pick up its slang meaning of awesome.)
The key, as already stated, is that language is a communication tool. To effectively communicate a word must mean the same to speaker and listener. For the shadowrun community as a whole, clip and magazine have a commonly understood meaning. That meaning is different from that as assigned by current pistol and rifle experts. For that matter, clip and magazine mean yet another thing when speaking to artillerymen or naval gunners.
So when you're talking to your fellow shooters at the range or in the field, feel free to be annoyed when one of them uses "clip" to refer to a magazine. Outside that community, however, FastJack had exactly the right attitude.
Now who's being pedantic?

An M1 uses a clip...whether it's an en bloc or a stripper clip or a half-moon, they're all clips and behave like clips. Clips load magazines.
The simple fact is that they used the wrong terms in the Shadowrun books, so that's what the community uses. If the books used the right term, the community would use the right terms. They got "katana" right in the books, and nobody says "Samurai sword" that I've seen, despite all of the Street Samurai running around.
Linguists may argue that "common usage" is just as valid as the correct usage of a word by an expert. Anyone other than a linguist generally accepts that there is a right and a wrong way to use a word, and the expert trumps the layman.
What I don't get is all of the pushback on this topic. If I were calling a fuel injector a carburetor, and someone explained the difference, I doubt it would be torch and pitchfork time...but correct someone on the difference between a magazine and a clip around here, and it's Holy War.
I don't think anyone (other than kirk

) is arguing as to which usage is correct - the most basic research will quickly determine which is the proper usage. For some reason, though, there's a lot of discussion as to whether people should use the words correctly. I find that baffling.
-Jn-
Ifriti Sophist