I suspect the Master knows, but all I could find was this where Una mentions
Bobo
OK, so the main thing is size and velocity is secondary. The 9mm that is just barley supersonic may make just as big a bang as one that is 20% or 30% faster. Well alright, ignorance fought! 
Regards
Testy
Yeah, it’s really tiny; the .223 is a much smaller, less powerful round than a 7mm/.30 caliber rifle round, but that thing–if it works as advertized (I haven’t seen it in use)–is a big jump ahead.
The aerodynamic conditions and resulting shape and intensity of a supersonic shock are highly complex; it’ll definitely change primarily depending on the shape of the ogive, the profile of the bullet, and speed. Part of the reason boattail rounds are so useful is because they help minimize normal and detatched shock. However, none of this is going to make supersonic rounds significantly quieter.
It’s a pity that there is this Hollywood-fueled ignorance about the use and value of silencers; they’re really not of much value to criminals (who typically know little about firearms anyway) and as you note, quite useful for noise abatement and often required in many European countries for hunting or recreational shooting.
Stranger
I’ve fired a military-issue (experimental) suppressed M-16. The supressor looked like a slightly over-sized fore-end sleeve, and did not extend the length of the barrel any beyond the usual dimensions - 16 inches, give or take a fraction. It was so effective that the sound of the action cycling was quite effectively drowning out all other sounds from the weapon. What it sounded like, down-range, I don’t know, but the single loudest sound I heard was the recoil spring operating.
The suppressor was perhaps 3" in diameter, and extended along roughtly the entire length of the barrel. This is NOT the kind of suppressor you’d add after-the-fact, as it was quile literally part of the barrel, and the barrel was ported along its entire length.
OTOH, it was so quiet, that Hollywood would have had to add noise to make it believeable.
My next door neighbor owns a Ruger Mark II .22 pistol with an integrated suppressor. It is sweet looking, and with subsonic ammo, all you hear is the click-click as the action cycles.
It’s not that hard to get, although some states have their own laws against them. But here in FL, you pay the price of the gun & suppressor, PLUS a $200 tax and fill out paperwork. You have to submit fingerprints and undergo a thorough FBI background check. But as long as you are otherwise legal to own a firearm (no prior felonies, domestic violence conviction, some others) the BATFE will issue you a permit for this gun in about a month.
It’s basically the same rule as buying a legal machine gun, but with the supplies of those drying up, be prepared to pay up in the 5 figures for one of those!!!
Tranquilis
That’s an interesting and probably overdue concept, making the rifle/pistol silenced by design instead of as an afterthought. How accurate was this? Was there any noticeable change? The site Stranger referenced claimed that velocity and accuracy actually improved using their new design of silencer. I’d have to see some numbers by a disinterested party before I believed that. It sounds too much like getting something for nothing.
Thanks
Testy
jtgain
I had no idea it was that simple. I’ll have to get one of these puppies when I move back to the US. As far as machine guns go, I used to be fascinated by the things and my father (a cop) actually owned a legal Thompson, one of the ancient, heavy ones with no stampings.
Since then, I’ve fired a lot of different automatic weapons and generally don’t care for them. One exception on that. I was in Dixie Gun Works several years ago and they had two genuine Gatling guns, one chambered for 30-06 and the other in 45-70. Beautiful things made from black Walnut, cartridge brass, and blued steel. Alas, one was $14K and the other was $13K so I had to let those good deals go by me. 
Regards
Testy
The design is now more than 20 years old. It’s been done in similar ways since on other kinds of weapons, but has not been adapted to general issue M-16s for reasons unknown to me. Speculation: Possibly it might have to do with cost, or with maintenace requirements. The barrel of the rifle was ported down its entire length, with the ports being very precisely graduated in size so that high-pressure gasses would set up a standing shockwave in the port that would prevent leakage of gasses until the pressures in the barrel had dropped below a certain point - IOW, once the bullet had accelerated to a certain speed and passed far enough down the barrel, pressure would drop low enough that the shockwaves would dissapate, and gasses would start venting into the suppressor, meaning that just about the point the bullet was leaving the muzzle, barrel gas pressure was suddenly dropping sharply, effectively eliminating muzzle report.
Needless to say, if you get port size and placement wrong in the least, you’ve just ruined a perfectly good weapon. Such precision work is expensive. Also, the supressor must’ve required more than a little bit of extra work to clean and maintain.
My experience with this weapon was that it was every bit as accurate as an un-supressed M-16, though it’s hard to be precise, because it was also equipped with some very nifty large-diameter, low-mag, light-gathering optics, and other soldier-proof aids to accuracy. One supposes that an un-suppressed rifle with those same aids would have been just as accurate. As it was, with an un-zeroed rifle, I was getting off-hand first-round hits on human torso-sized targets out to 250 meters without any trouble at all. All in all, a very pleasing weapon, but very likely a very expensive one, too.
The MP5 has an integral suppressor, apparently since 1974. It isn’t a new concept.
Any suppressor with non-wiping baffles shouldn’t decrease accuracy, although it will usually require re-zeroing the sights. It should also act as a very effective flash hider and recoil reducer. It makes sense that a non-wiping suppressor should increase velocity, since it effectively increases barrel length without adding any friction.
This youtube video is supposedly footage of a De lisle carbine being fired. The camera position is mostly downrange, quite close, and you can hear birdsong and extraneous noise quite clearly. If genuine, the thing is quiet.
Tranquilis
That’s amazingly accurate compared to what I expected. Thinking back on it, I’ve probably seen weapons using similar technology but assumed it was just a barrel shroud. Some of the local security forces around here have something that may be silenced using this technique. I’ve seen a few guys running around with a very short submachine gun of some type with a completely shrouded barrel. The magazine looks like it takes something larger than the common 9X19mm round. The thing is almost small enough to be some kind of large pistol.
I wonder how much this would really add to the price if they were mass produced. While the prototype you wre firing is probably hellishly expensive, I’d think that mass production could cut that in half. (Just a WAG on my part.)
In any event, my thanks. You’ve reduced my ignorance.
Regards
Testy
And that would be the cheap part! The 45-70, at a buck or so a round, would cost a fortune to play with! But when I win the lottery, I’ll be all for it!! 
Matt
Thanks for the fascinating video. I want me one of those things! I saw (and heard) quite a few MP-5s right after the first Gulf War but those were not nearly as quiet as the De Lisle or the m-16 that Tranquillis referenced. The weapons I saw/heard were captured or abandoned by (I assume) the Iraqis and could have been suffering from poor maintenance or the wrong ammunition. (If they were spec-ed for subsonic ammo) I’m unsure. The sound level was suppressed but not to the extent we’ve been talking about. Interesting.
Oh well. Thanks again for the great reference.
All the best
Testy
Butler
Yeah, feeding it would be a beast of a bill! One interesting thing about those. AFAIK, there were no licensing restrictions or anything like that. I believe you only had to be a Tenn. resident and have the cash. Of course, iif you could afford to buy one of those you probably weren’t going to be holding-up liquor stores with it!
Regards
Testy
Tranquillis
Just something I forgot to add. You have my undiluted envy for having access to this stuff!
All the best
Testy
I was on active duty with the Nav at the time, and my father was chief engineer for Human Engineering Labs at Aberdeen Proving Grounds. HEL specialised in ergonmics and human factors, including how to make weapons more efficient and user friendly. When I was home on leave, he’d sometimes use me as a “joe average” tester to get my reactions and see how stuff worked for an unfamilliar user. I had the clearance levels, and was available. Plus it allowed some “diggit” time between the guys. 
I don’t know why a lot of the experimental stuff they worked on never made it to the field, but then, it was experimental. I’d have loved to see those combat optics make it - very low-mag, only about 1.5x, but enough to make a substantial difference in accuracy, and they were wide lenses with a huge FoV, meaning you could easily and practically acquire targets even when in a hurry. On top of that, they gathered light like a sponge, and were physically quite compact and robust. Good design, all the way 'round. Probably cost a small fortune, though.
The suppressed rifle, even supposing production costs were substantially less than the prototype, would still have been way more pricy than the base A2 off of which it was based. And that still doesn’t address the maintenance issue - I suspect fouling would’ve been a cast-iron bitch with that puppy.
All that said, the M-16A4 has many of the features the protoype I handled displayed. This stuff does percolate through the system, even if it looks different when it finally arrives.
Ooops - out of the edit window timeframe:
Sounds like one of the suppressed MP5 family, or similar.
If they were classified as a long rifle, then you wouldn’t even need to be a state resident. I can buy any normal rifle or shotgun in any state I’d like. Handguns can only be purchased in a home state, or shipped to the home state for transfer.
If you mounted it to the back of a pickup truck, could you use it to hold up the drive through liquor stores in TX?
Likewise when firing a Brit. silenced military issue S.M.G.the only sound you can hear is the bolt going back and forwards.
Here’s a video of the suppressed version of the MP5 firing. As advertised, the action cycling is louder than the report. The louder booms you hear are obviously another rifle on the range firing. So, suppression does not exactly produce the chirp you hear in movies, but it can be damn quiet. I’ve heard that the MP5 is particularly good though.
I found a video of someone trying the 2-liter bottle silencer on two different pistols. No surprise, it doesn’t reduce the noise appreciably and is visibly dangerous. The gas from firing builds up inside the bottle and blows back at the operator through the imperfect seal at the neck of the bottle, and when the pressure is released, either through the pressure rupturing the bottle or from the bullet puncturing it, there are shards of plastic flying everywhere.