I'm curious how gas vents can possibly work with suppressed pistols.

With gas vents, the barrel is ported to release gas through the holes in the barrel as the bullet passes each hole. The result is less muzzle movement, a drop in velocity (requiring hotter rounds to "feed" the ports) and a louder report.

Suppressor function:

http://en.wikipedia.org/wiki/Suppressor



So, how is it that a gas vent with suppressor could possibly work? If the gas vent is placed before the suppressor, the escaping gas will make a lot of noise. There isn't much left after the suppressor since it bleeds off gas.

So, is this just a magical feat of engineering known only to the Shadowrun writers?

If you look at the fluff and rules, Suppressors are not compaitble with Gas Vents (i.e you cannot use both simultaneously)... now the gas vents you describe (and what are most common today) are known by a least one name "Magnaporting"... and yes, this would be somewhat unuseable with Suppressors... but I can see some venting technologies that might actually work well, though not in tandem...

Just my 2

Who knows what may come along over the next 60 years or so...

"So, is this just a magical feat of engineering known only to the Shadowrun writers?"

Yes.

But then again, I don't let players add silencers to their pistols in the field. Extremely fine threading which can be cross-threaded very...very...easily.

Gas vent doesn't increase the report of the shot, it is redirecting more of it back towards the shooter so it seems louder.

They, uh, don't. They're both barrel mounted accessories, so you have to choose one or t'other.

They don't work together at all.

It's in arsenal. If you have one, the other doesn't work.

You can have both installed on the same gun mind you. But you're going to need to either close the gas vents and use the suppressor, or leave them open and get the extra RC.

If you're not using arsenal... then w/ BBB only technically a gun w/ an internal suppressor could use gas vent as a barrel mod, but I'd recommend against it.



Sidenote:
Did the board just change it's default font... I've gone from my nice comfortable small font to a new one about 1-3points bigger it seems and it's really annoying.

I haven't noticed a problem, but then again, I don't use the default font. *grin*

Working the same as it ever has for me.

Check your browser's text zoom setting.

Half of this post is new information, and half of it is a recap for those who were sleeping in class.

Another thing we are all forgetting is that Gas Vents are incompatible with pistols. Gas Vents can only be added to Machinepistols, SMGs, Assault Rifles, and Machineguns. For all of them except Machineguns you can also add a Suppressor (At least one of the two must be added as an internal modification.), but you must select to have one or the other active at any given moment.

I've been making the assumption that the ports on the Gas Venting can be closed to allow the gasses to pass through the Suppressor correctly. Open = Gas Vent but no Suppressor, closed = Suppressor but no Gas Vent.

- Umbra

Not an assumption, omae. That's fact in the RAW. Can't remember if it's the BBB or Arsenal at the moment, but it IS set out clearly that you do it that way.

Thanks all. That's what I was looking for. I was browsing "Best Heavy Pistol Set-up" and saw GV and suppressors on a Ruger Thunderbolt.

Correction... gas vents are incompatible to be installed as modifications or accessories to pistols.

IF the pistol has a gas vent built in off the assembly line (some do), then it is quite valid. There's a lot of guns which have various things built in which they're not supposed to (pistols w/ underbarrel mounted items from the factory for example, as there technically is no pistol underbarrel accessory rail!).

And the rules still specifically allow you to combine a gas vent with a silencer or sound suppressor, you just have to decide which one you want the benefit of and spend either a simple or a free action to open or close the vents on the gas vent.

Why are you venting a pistol anyway? If you need something for rapid fire (Rutger or Barretta) carry a seperate pistol for silencer work.

The OP was asking how both could operate and provide benefits at the same time. Or that's how I read it, anyway

Yeah, we were just explaining why it can't work. People are offering up explanations via rules and via logic to show why you can't have both together.

Ran across an interesting bit on the Military Channel.

Turns out that Cheytac has managed to create a setup on their M-200 Intervention that allows you to fit a suppressor onto a gas-vented barrel. Now...I may have heard it wrong but I hit the rewind twice and they said that on the M-200 you could fit their suppressor without swapping out the barrel. And they didn't make it sound like you had to remove the gas vent...so...I guess I was wrong. Even so...in this situation you are getting either the gas-venting or the suppression of the weapon's report...not both.

Fitting a suppressor onto a sniper rifle and still maintaining the accuracy is pretty impressive by itself. I would dearly love to get the opportunity to take any of their weapons out to their target range for a spin!

actually that is probably flash supression rather than recoil compensation since it is a sniper weapon and they probably aren't worried about throwing a lot of lead down-range quickly. And flash supression is mostly so that the person firing the weapon isn't blinded by the muzzle flash more than anything else. But maintaining the accuracy, you are correct, that is pretty awesome engineering.

Uhmm... yeah... just watched the whole thing again. Outside of my dislike of the program for it's outright cheerleaderism (and some of the poorly reported stuff like dragonskin) I don't see anything there to support your assertion.

1. I know of no precision sniper rifles which use a gas vent. (they're less precise and introduce an element of uncertainty unwanted in a sniper weapon)
2. all suppressors hide muzzle flash (flash is unburnt powder when the round leaves the barrel... it's a lucky accident of the way suppressors work)
3. flash hiders are common on even AR's and many people confuse them w/ vents (purpose is to prevent the shooter from being night blinded by his own flash, not to hide the flash from others).
4. Suppressors are very accurate provided they're securely attached and the baffles are well made. Once securely attached they're very repeatable (normally just a matter of knowing how much higher to hold at various distances). So I don't share the awe about the suppressor.


The purpose of a gas vent is to help automatic or rapid-fire weaponry (mostly pistols, SMG's, AR's) where you're firing a lot of shots in rapid succession and need to limit barrel climb. In order to do this, the gas must be vented w/ some velocity (newton 3rd law), if it has velocity then it has sound. Reducing the velocity below supersonic (eliminating crack but still a loud woosh) reduces the effectiveness. (you either need a LARGE volume of gas at small velocity or a small volume of gas at high velocity.

Also speaking from experience... simply attaching an external suppressor to a weapon limits it's muzzle flip and recoil characteristics (think of it as an underbarrel weight). Though SR doesn't do this... and it doesn't really bother me that it doesn't (especially for internal suppressors).

Well its the nature of whats causing the recoil. An underbarrel weight or a weight barrel seem to help recoil for the first few shots, BUT its not fixing the problem at all. Due to the fact that the recoil will be coming from a constant source (assuming multiple rounds fired) and the method of compensation is static (weight).

The next problem with recoil compensation lies within its necessity. In what situation do you need to have large amounts of recoil compensation? Most weapons capable of firing in full auto are either fired in burst 4-8 rounds, or used for supressing fire. With the first its to counter act the recoil, firing 4-8 rounds at a target insures a hit more so than 1, and supressing fire does that and doesn't necessarily need to be pin point accurate. Any weapon that is used as a lead hose, has such a high rate of fire that recoil isn't a problem because when you place 50 rounds in a 5'x5' area you are putting around round at ever 6 inches. You are bound to hit what ever is in that grid. Anyhing larger than that area warrants artillary.

slightly on and off-topic. I heard that there was a weapon (smg or assault rifle) that was designed to not have any noticable muzzle rise from actual recoil. They said it was on come discovery channel show or something and that it was a butt-ugly weapon cause the bolt recoiled in a downward arc or something.
I, however, didn't see the show and have never heard of it before. Anyone able to talk about it at all?

Look at sniper rifles and their usage. Police sharpshooters have sniper rifles and typically don't need to worry about hiding from the enemy. Military sharpshooters tend to engage at much much larger ranges. Typically you "hear" a military sniper because you hear the bullet flying by you. The round fired from a typical 7.62 leaves the barrel at super-sonic speeds. When a bullet at super-sonic speeds passes by you, you hear a crackling effect. However, given the distances involved in military sharpshooting, after about 600 meters air resistance causes the bullet to slow to sub-sonic speeds. By 800-1000 meters shooting it's very difficult to tell that a sharpshooter is firing at you unless you see the round impacting something. Or according to a US Army Ranger Sniper, "If you're shooting at a target 800 or 1,000 meters out, you could be shooting at that person all day long and they don't even know they are being shot at."

The moral of the story is that if you're sharpshooting at the "long" range for the sniper category, you should be worrying more about hiding yourself than the sound the weapon makes. In Shadowrun terms, you should be using camouflage or chameleon suits to "break up" your profile and have a camouflage covering on your weapon. Consider the usages where you would be sniping at this range. Wetwork or fire support for other runners. If it's wetwork, you're likely making a few shots before getting out of there, so you should already have your fast escape planned. If it's as fire support consider this... those trying to hear your shot are likely suffering the following... distract (-2), you're far away (-3), interfering sound (-2) (the other runners are likely shooting guns too), and if the GM is feeling particularly cruel stack the not in immediate vicinity (-2). So that's a -7 penalty just to hear the sniper, -9 if the GM is cruel. This is on a 1 threshold. For most NPCs, it will be impossible for them to even hear it, if you consider the "average" NPC would have 3 Intuition, and -maybe- 1-2 perception.

For seeing the aforementioned sharpshooter, taking the same NPCs they would have the distraction (-2) and far away (-3) penalties. If this is a nighttime run you're in low light conditions, unless it's pitch black (unlikely since the moon would almost always be casting ambient light), they're having a -2 penalty for normal vision. You're still at the -7, except you have camouflage or chameleon on, which inflicts an additional -4. So they're at -11 to see you on what is at least a 2 threshold.

I sometimes wonder if the range penalties to perception aren't harsh enough.

Wow... some people really have zero real world experience w/ firearms and it really shows. And it makes reading these posts both funny and sad.


Never been in the woods during hunting season, have you StealthSigma... you have any idea how far a rifle reports carry?! I didn't think so.

Lets just say that you can hear them easily for miles, they stand out. (varying on terrain, woods muffle a bit, canyons and mountains quite a distance)


Your assertion that no sniper would even need to bother w/ worrying about sound and a suppressor is also drek. I quote:
"you should be worrying more about hiding yourself than the sound the weapon makes."
BS> it's trivial to hide giving visual mods... it's harder to hide sound which has a distinctive signature and carries for miles (so it's definately in the area and not far away). Even going back to civil war days... people typically heard the battle LONG before they could see it. (in fact, most people take specialization visual on perception because there's a lot more penalties there).

The above is true ONLY IF THE WEAPON IS SUPPRESSED! (emphasis necessary) You have the first part right about bullet noise and the ballistic crack. However, you have the second part dead wrong, there is also a sonic boom produced by the weapon which the suppressor is designed to muffle. (yes muffle, there's very little difference in theory form a car's muffler and a suppressor). Most people don't realize that the sound of a gunshot is the sonic boom created by the gas escaping the gun.

Also if you don't use a suppressor, I'd give a bonus for seeing the muzzle flash. (no flash hiders do NOT hide the flash from others, they hide it from blinding the shooter!).


Now for the third part... your assertions on mods.
For auditory data... Distraction -2... interfering sound -2 possible depending on location... sound is definately in the area so that one does not apply (visual and audio does not necessarily operate on the same scales). Sound stands out (+2) (you tell me any place where gunshots don't stand out and you're in a pretty bad neighborhood). That's only a single -2. The rest are silly (you're double penalizing for both far away and sound not in the area... yeah right). Far away is a tough one and

If you don't believe me, you're the runner... do you gripe and claim that 'police sirens are loud and stand out' So even though I can't see them, I'm definately so far away that I should get the full -5 to notice them. No... they stand out for quite some distance easily a half mile w/o too much penalty. Gunshots... police sirens... same difference.

Also, in your visual case you're not on a threshhold, you're rolling opposed against an opposed stealth pool.


Now onto silliness in the perception rules:
Anyone else notice
Threshhold 1: gunshot
Threshhold 2: suppressed gunfire

If the threshhold goes up... then what's with the -4 to -8 penalty (mods, accessories, and ammo) for actually using a suppressed weapon on the sound perception roll.

Mind you perception says if they get 1 hit at all they know something is going on, just not necessarily what. Increase the amount of info you give for each hit according to the chart.

hi hi

I don't know of any way to suppress the sound of the sonic boom created by a supersonic bullet. Am I missing something?

You don't..

A supersonic bullet produces what's called a ballistic crack. (small object travelling supersonic)


To better explain, why it's normally easy for a person to ascertain where a gunshot game from... the bullet arrives before the sound, and you hear the ballistric crack (this comes form the direction of the bullets closest point of approach, so it's misleading, but it alerts your senses). You then hear the deeper rolling boom of the gun, and your alert senses have a much easier time realizing what direction it came from.

Same goes for longer ranges... if the bullets slowed down to go subsonic (and there are rounds which are designed specifically not to be supersonic avoiding the crack). You won't easily hear it. However, even w/o the forewarning... the rolling boom of the gun normally stands out and is fairly obvious in it's direction.


When dealing w/ suppressed shots though. You don't hear the rolling report of the gun. You hear the deceptive crack of the bullet passing you (if it misses), which makes it much harder to localize where the shooter is. That's the value of suppressing a long range high velocity rifle.

First of all the situation I put forth where I placed modifiers was in a sharpshooting fire support situation for a group of runners engaged in battle with an enemy. That would universally apply the distracted and distance modifiers to the dice pool. If they are engaged in a fire fight, I would assume that the gun fight they are engaged it would qualify for a suitable interfering sound at the very least it would negate the +2 bonus from sound stands out. Also, I said if the GM decided to be cruel he could apply both distance penalties. Regardless, in the situation I described you're facing a -5 penalty at least. For characters with an average of 3 intuition and 1-2 perception skill they cannot hear you without augmentations (5 - 5 = 0). In other words, the only hope for a character to hear you is for them to make a Long Shot roll using edge.

As for why I say you need to worry about visual more than sound hiding? Pinpointing. 1 success on a listening test tells you I'm around, 1 success on a sight test tells you where I am. I would believe it more likely for someone to locate the position of a sniper by analyzing bullet trajectory than by pinpointing their position via listening. Simply, no matter the terrain you're going to have a very difficult, if not impossible time telling specifically from where the shot came. Yes, you could tell direction, though echos would make that more difficult, but I wouldn't expect anyone other than a highly augmented character with a high intuition and perception skill (at least 5 in both) to be able to have a -chance- at pinpointing something at range based on sound. If hearing a suppressed weapon is a 2 threshold, then pinpointing any weapon is going to be at least a 3, if not a 4. So while you may always be able to tell direction, I highly doubt you could pinpoint the location of a sniper based on a single shot, if at all. A listen check against a sniper is usually going to lead to one of the two results, either the character use the direction of the fire to make sure they have cover between them and the sniper, or they use it to attempt to visually locate the sniper. Thus stacking protection from being located visually is far more valuable and prudent than stacking protection from hearing based checks.

Edit:
Further, the use of suppressors on sniper rifles will be typically used in military special forces. They also don't take as many shots as combat snipers, and they don't always have the support of other infantry. A combat sniper, especially one engaged in a blocking action but also snipers in overwatch actions, will be more concerned about rounds down-ranged to help protect the infantry that are under assault from an enemy or as they assault a position. Now if a suppressor is built into the rifle, that's great, but since any attached suppressor fouls up the zeroing on a sniper rifle, they may not be so hot, or necessary, if they're detachable.

Actually, I would say that it would be easier to hear a non-suppressed Weapon (Threshold goes down) over a suppressed weapon... thus the thresholds would NOT increase for Non-Suppressed Weapons, contrary to the above statement...

EDIT: Of Course... If I would just read the post... Never mind... You are talking about pinpointing, not noticing... My Bad...

I still contend only a small penalty... I wouldn't use the -3 at all. And again, my example was for an actual sniper making a cold barrel shot... not for a designated marksman providing precision support fire. (there's a big difference)

And if you're in a firefight... you're not distracted. All your senses are focused on things like gunfire and where it's coming from. I was referring to the initial sniping test... not to someone actively engaged in a firefight. Especially one who's aware there's a sniper present somewhere if not where.


Distracted is things like walking down a crowded city street and watching everything and anything. Or you have no particular reason to be alert. Or you're focused on doing something special... like someone trying to focus his attention on something technically difficult while his opponents cover him (such as defusing a bomb... I'd call that distracted). Another case for distracted is AR spam zones. Driving and noticing something happening on the sidewalk. Not, I'm in a firefight... I'm not paying attention at all to where people are shooting at me from. So I disagre on the -2 once a fight is joined.

Far away for a sound, maybe if the shooter was a mile away... but no. For most applications of loud sounds, there's a different sense of scale. Again, if you can hear the star's sirens at long range... you can hear a shot at long range just as easily. Two way street. Again, you don't get my meaning distance has different meaning to very loud sounds than it does to normal events and vision. Long range for vision and sound are different things.

Interfering sound... yeah other gunshots! That's a surefire -2 in a firefight.

Sound stands out... it's a gunshot... hell yeah. +2.

At this point it's a wash... no dice pool penalty... except the silencing on the gun (which can be a whopping -8 if you have internal, electronic firing, and firing subsonic rounds). At this point, the target would need 2 net hits to locate you based on sound. 1 hit tells him he's been shot at (gunshot).



As far as bullet trajectories... IIRC they have systems now which can track a shooters location from it's ballistic crack. So sound location systems are not all that far fetched. And there is good cause to be concerned about them.


Please stop... your edit is laughable:
It moves the zero... it DOES NOT SCREW IT UP. If I have a can on... I hold 6" high at that range.... Cans are extremely repeatable... and not that uncommon to issue. The bigger problem is they get hot very quickly and require cooling if firing a lot of rounds. (some will poor water in them for this use). Once I know the ballistics, the changes are easy to note, and normally only a problem at extreme sniping ranges.

The situation you describe is a classic defination of the squad designated marksmen. A role which has now been officially reintroduced and actively trained. Even to the point of actually issuing battle rifles again (finally) as they've finally figured out that the M-16 is NOT a gun for all occasions. (and the M-4 even less so).

Edit:
I give up... there's no point in trying to teach people. Most of them talk out of their asses, have never fired a precision rifle. Have never even tried firing a hunting rifle at 500yards and wouldn't know the difference. They've never used a suppressor (generally illegal in the states so understandable). If they've ever been at a range haven't been out during even the first day of deer season (to hear how far away they can hear people firing around them)... let alone in a combat zone. And most would rather sound cool, by spouting off stuff they hear and see in the movies.

I don't know... Having been under fire on occassion, I would say that I was somewhat distracted by the individuals in my immediate vicinity firing at me, I probably would not have realized if there was a Sniper taking shots at me at all... hard to distinguish a distant sound source from the immediate firefight, that distant sound will tend to blend into the local audible carnage of the firefight...

Tymeas:
I can buy that.

Quite frankly... it'd probably depend on the NPC... whether it was a private, or a noncom who knows better and needs to provide leadership. Of course he'll probably have a bigger perception pool also.

Just I disagree w/ so many penalties as he has that the audio perception pool has been completely destroyed. Just to HEAR a guy firing at you w/ a hunting rifle.



Really, the reason snipers aren't supposed to fire twice is this. The first shot alerts people there's someone there and they need to pay attention. Then they're looking for him. The second shot drastically increases chances of being localized. That means a much worse chance of sneaking back out.

And with this I am in complete agreement...

It is amazing exactly how far you can hear gunfire... though supressed gunfire is generally a lot harder to hear, it is rarely completely silent...

Keep the Faith...

Keep in mind, you only need a single success, and the average person has an intuition of 3, so without modifiers, they're going to hear the thing. Now, the modifiers in question actually assume a certain amount of background noise and poor acustics. The dice pool can go UP a lot if, for example, you were in the woods, it was completely quiet with little or no wind, and you yourself are being quiet. There, the sound travels a HECK of a long distance, but can you localize it? I think that's a large part of what the check reflects in the first place. That being said, your average hunter, if they actually bring anything home besides empty beer cans, probably has actual rangs in Perception; They've trained themselves to pick out telltales and ignore sounds that aren't important. It's not going to be a really high skill, unless they're a champoin hunter of course, but all the same, I would say to "hear" an un-silenced rifle shot up the street, anybody who's a) paying attention b) not listening to music on their IGizmo c) hasn't previously damaged their hearing listening to same at just-below-bleeding-ears for years and d) isn't naturally oblivious should have about a 50% chance - minimum - to hear that rifle shot on the busy city street and not confuse it with a backfire or something similar. THAT'S your key, there. If it's un-silenced gunfire, I would probably rule (as GM) that their pool never went below 1, giving them at LEAST a 33% chance of hearing the shot even under the most ADVERSE of conditions. Now, silenced gunfire? That's a diferent animal alltogether.


I can agree with that as far as it goes. Each shot will allow the enemy to better localize your origination point, but with proper camoflage, suppression of the shot AND the muzzle flash, range, and dozens of other MINOR but vital skills a genuine sniper learns, without sophisticated sensing gear, their ability to zero in on the sniper is going to be close to nil. Actual sniper training has instructors, who have the benefits of time, excellent optics, tons of experience, and the assurance the sniper isn't shooting at THEM, whose job it is to spot sniper students after multiple shots at relatively close ranges, and a passing grade is for them NOT to be able to spot the student at all, even when they know more-or-less where they HAVE to be. Now, add in some really high tech gear properly utilized and deployed, and you can get a LOT closer bead on where the fire is coming from, even on the FIRST shot, but that's another thread entirely since we're talking about a (meta)human's perception pool.

Hmm, a guess a slightly off topic question would be, why shouldn't someone be able to gas vent a pistol if they wanted to?

Um, you lost me. Why COULDN'T you gas-vent a pistol? Is there a speciffic prohibition against it I never bothered to pay attention to because I never had a pistol the had enough recoil to matter or that I hadn't modded with things that provided enough RC so I could ignore it in any case? It's a barrel-mounted accessory/modification, and if you did something silly like, say, a full auto conversion of a Colt Manhunter, I can see where a gas-vent would be HIGHLY appropriate to the circumstances.

Unless I've missed something no, gas-venting a pistol isn't allowed under the rules, I was asking if there was a reason that it might not work in real life.

As a disclaimer, I've personally house-ruled the issue to allow gas-venting.

Um, the entire Glock "C" class in real life includes what I would consider Gas Vent 1.

That's not a need for a house rule, it's a need for a "Duh-Check".

Now I need to go read to see if they are actually BANNED in the RAW.

*shakes head sadly*

Karenshara:

I'll vouch... the rules explicitly state that you cannot add a gas vent to a pistol (either as a barrel option, or as a weapon modification).

There's a lot of pistols which have it built-in. It's not uncommon to find 'unique' weapons with modifications built-in they normally couldn't get (or my other favorite... R rated guns w/ F-rated suppressors or GL's built in!).

IMO: doesn't really matter if it's house ruled or not. How many pistols need more than 1 point of RC anyhow.

That's just it, isn't it? Besides the "major ROF conversion - Full Auto" I mentioned above, it's pointless, when personalized grips or electronic firing will do just fine.

Actually... you need 5 points of RC if you have a BF pistol.

-2 for the first simple burst, -3 for the second.

So there is some point to getting a gas vent on those.
Though I think you can manage 5 points of RC in extremis for the one BF pistol... (folding stock, personalized grip, underbarrel weight, 2 point special RC built in)

I guess my question would simply be this: Why mod your Pistol into a Machine Pistol? Just get a Machine Pistol instead...

Because I can?

Um... 5P/-1 and 2 points better concealability?

Because the gun comes off the shelf w/ BF w/o any modification! (which allows modification to full auto for *1* weapon upgrade slot).

Because a heavy pistol has a 5P/-1 damage code instead of a meagre 4P... and Karenshara is quite right on the concealability.

(what 4 BF pistols that I can think of... fabuki, fichetti, and 2 heavy pistols IIRC).

All Valid Points, Just thought that I would ask...

Though I would argue that adding all those modifications to your weapons will impact that Concealability that you are so fond of, bringing it up to the Concealability of your Heavy Pistol to that of a Machine Pistol at the least (your damage rating will still be golden)...

Though if you were using a Light Pistol, you still might end up with a better concealability (0 instead of +2)... of course, there goes your damage rating...

Interestingly enough, it doesn't. Only a couple of the mods have a "concealablity" (read: size) penalty. Long Barrel and Extra Clip come to mind. I don't believe the ROF mod is one of them.

Chameleon coating, but that's a penalty to the opponent rather than the wielder.

which is how all of the weapon concealment rules work.

It's about as close as we're going to come to a physical size reference.

I can agree that there is no information for size increases by modification (save for a very few "modifications"), however, those new pieces have to fit somehow... and if you are making a Pistol into a Machine Pistol, well, then you have a Machine Pistol (by Fluff, if nothing else) and I would enforce the Fluff Descriptive, Mechanical rules concealment for Machine Pistol...

But that is just me I guess... YMMV of Course

Keep the Faith...

Well, now we are getting completely off topic but the real difference between the machine pistols and pistols with BF or FA capability is the fact that machine pistols actually have the ammo capacity to sustain it for more than a few seconds. Most of the BF pistols have ammo capacity around 12-18. Meanwhile the MPs all have around 30+ ammo. The only exceptions are the Fubuki and the Ares Viper which have 40 and 30 respectively, both of which have specialized mechanisms or ammo.

I think for the most part, the difference in concealability between pistols and MPs has to do with their expanded clips. Which is why even though the rules don't explicitly say so, adding a silencer to a pistol or any other weapon could be houseruled to increase its concealability in certain circumstances. Perhaps for example when trying to hide it in your sleeves rather than within a concealed holster under your coat.