Sure, it's way too long to break out the calculator and scratch pad for every shot. What I do is keep those numbers in mind and wing it based on what sounds right (Hmm 300m away on a crowded street at rush hour, and there are buildings in between? Sounds like +10. Oh, it's silenced... uh, call it +0 then). Once you get the feel for the numbers, it's quick and easy.

Plus, if you're the GM, it's dirty and arbitrary enough to be a consistent system without tying your hands.

My point is simply that ranges for weapons have been drastically reduced to make melee more viable in the game world. It is done for practical reason. So, why should we worry so much about the reality of wave functions and interference? It makes sense to myself and players to apply modifiers in a fixed manner depending on the type of weapon being used and the surrounding environment of course. If the person is riding atop a baneblade with the engine roaring, I'm going to apply a negative modifier. It also makes sense to have a pistol be less audible than an autogun or a hunting rifle. That is why I use the range of the weapon for applying modifiers. And it doesn't mean that after 150 meters nobody would be able to hear a pistol, it simply means that there would be larger negative modifiers.

A rifle only being able to shoot 400 m is ridiculous in my book, but that's how the game is.

It also makes sense to have a pistol be less audible than an autogun or a hunting rifle.

Except it doesn't, not by that much. Don't use my numbers if you don't want, if nothing else remember that a low powered pistol shot (.22 short, about as weak a round as you can get) is 140 db, roughly the same as a jet engine. A much shorter sound, yes, and therefore much much harder to trace, but if you're around one you're going to hear it. A 12ga shotgun is around 155, a .30-06 is around 160. So basing it off the weapon's range, while maybe consistent and easy to use, is flatly ridiculous if you think about it for half a second: a shotgun has the same range as a stub automatic, but I doubt you'd rule that they're the same loudness in-game basing loudness off of anything other than weapon range.

Actually, looking back over the thread, I think we have a misunderstanding. I was addressing Phi6891's post with my bit about the unhearable kill, not yours, since he specified that in his games shots can't be heard beyond max range. Although I do disagree with you that pistol rounds are much less loud than rifle rounds (IRL, the .44 Magnum clocks at about 165 db, well over the 160 for the .30-06 which is reasonable to use for a hunting rifle; the 5.56NATO, a reasonable stand in for an autogun since it's the modern assault rifle cartridge, clocks about 155, or about the same as the shotgun). Wing it for speed, but at least make your system somewhat consistent with reality, or else you wind up with the "shotgun is just as loud as a .38 special but both are quieter than a .22 varmint rifle" nonsense that kills suspension of disbelief in some players.

You want something quick and dirty without numbers? The larger and faster the round (more Pen or whatever the plus to the d10 is), the louder it is. You can leave out special ammo if you want, on the theory that manstoppers don't add extra noise, they're just the same bullets with harder jackets.

My point is simply that ranges for weapons have been drastically reduced to make melee more viable in the game world.

I was going to say that range hasn't been cut down much, but then I looked up some range tables to be sure. Sure enough, the .223 (autogun equivalent) delivers 1000 ft-lbs of energy (rule of thumb for whitetail deer) at ~125 yards, and the .30-06 (hunting rifle) gets about 650 yards. So if anything, the game overstates effective range of the most common SP weapon (the autogun can wound out to 400m) and gets the standard sniper weapon about right (hunting rifle out to 600m).

So yeah, if it works for your group then all's good; but I'm used to playing with guys that go "Wait, what?" when something weird like that pops up. 'Course I need to mention that a member of my old group was a competition shooter, another is in the Navy, and I've been known to spend a Saturday morning at the range myself, so guns are something we know a little about.