ibo7

https://www.actionhobbies.co.uk/products/ics-pm2-non-blowback-pistol-black/
 
https://www.firesupport.uk/ics-pm2-non-blowback-pistol-nbb-black.html
 
 

It's worse. Even heavier than the mk23 and double action only

The ICS PM2 makarov is as quiet as the MK23. The only downside is that it doesn't have the after market support. The MK23 can be made to out perform everything. The PM2 scores very much on style and is a lot smaller. It takes a CO2 bulb but will chrono no problem. It has a very heavy trigger if you want to rapid fire it so it's better to cock the hammer with your thumb. If it had the same after market support as the MK23 it would probably be the go-to sniper backup but that doesn't look like it's going to happen. Still if you want something smaller than the MK23 and just as quiet, but don't need it to perform circumcisions at 70 meters it's an option. I like mine. I did buy the larger suppressor for it. And the magazines are little sticks that are very easy to store. 

So exactly like a mk23 then 😂

Those can be fun but my god is the trigger horrible

The quietest pistol you'll ever have.

Oh, is this for garden use rather than skirmishing?  The ASG Ruger is quiet, can be had for under £50, but comes in at 1.3J.  You can verrrry carefully file down the hammer to reduce that if you want to skirmish it.
 
If this is purely for slinging BBs at short ranges, you could also consider an AEP. Any of the CYMA AEPs will make more noise from the motor than the pop from the tiny cylinder.

The Makarov isn't that quiet. It has quite a loud pop from the CO2. Quietest is the TM MK 23 with silencer attached. Used to run around Copehill at night and my giggling as I shot people was louder than the pistol. 
If you fancy branching into small form factor rifles instead of pistols, I reckon you could make a TM VSR 1 pretty quiet.

Have you considered revolvers like the Dan Wesson 715 and th orange of Smith  & Wessons from Umarex.
Western Arms used to do some 1911 NBB which can still be found second hand occasionally, they are really Seecamp Double Action Converted 1911's.  There is also th excellent Tokyo MArui Range of NBB 1911 amongst others.

The range of nbb pistols is definitely a fraction of the size of the gbb market, I guess most people prefer blow back despite the disadvantages (and I'm certainly one of them). I don't think there are any nbb 1911s available but there is a Makarov
 
https://www.actionhobbies.co.uk/products/kwc-co2-makarov-airsoft-pistol-nbb/
 
I've no idea what they're like though.  I've never owned one as they're way too overpowered for skirmishing at over 1.5j but if you only want it for plinking that isn't an issue 

The split slide versions of Hi Capa's might be an option if you're set on 1911 ish designs. Less moving mass, so inherently quieter.

All non blow back pistols are quieter than GBB ones due to less moving parts. The mk23 just gets mentioned the most as they're the most easily available. Also being able to take a suppressor allows them to be even quieter.
 
Is there a specific model you're interested in?

The quietest aeg that you can make is most likely something like an Aug or previously mentioned an F2000. The gearbox is very enclosed and the areas around it can be padded out with foam and etc for further sound proofing. 
 
Although that's only if all variables between all the different aegs are constant. 
 
Noises come from every single part of the gearbox. The motor, gears, piston, piston head and cylinder head slapping and other bits. 
 
The fact is if you take 10 aegs out of the box. All the same model and from the same manufacturer you will find each one sounds different 
 
 
 

This. Also it's worth remembering that we're using things which are relatively mass produced and put together without any precision or tuning so 2 identical guns could easily produce different noise levels depending on whether they were put together at the start or 10 minutes before the end of shift

I got around that issue by short stroking the sector gear by two teeth, giving the whole thing a damn good shimming and fitting a high speed Warhead motor.
 
 
 
But I have more money than sense so your mileage may vary!

You are not going to get a good answer, no one has done any sort of noise comparison of a wide range of stock AEGs (or any that I can find). Even a custom build gun is going to make a minimum of difference to that actually decibel level from a gun. Mods will change things like pitch a frequency so the sound may not travel as far.

Suppressors do work very well on hpa/gas non-blowbacks where theres minimal action noise.

G&g ump with the suppressor; one of the few suppressors that actually work!

Out of the box the Cyma M14 is a particularly slow cycling, noisy gun. Most new ish M4s are pretty quiet if you run them on an 11.1v battery and make sure you adjust the motor height properly.

The f2000 would probably get a vote.
 
Reasonably long barrel for less muzzle pop, plastic body to dampen the noise and most of the noise being cradled by the shooters body is a pretty good recipe for quietness.
 
That said, it isnt that quiet as the user given your ear is right next to the box so i'm mostly relying on the comments of others.
 
Generally when it comes to quietness its usually hpa's and gas non-blowbacks (mk23, revolvers etc) that get mentioned, where you can be standing 6 foot away from the shooter and the sound of the bb's hitting the target is more audible than the gun.

Dunno about "as standard" but shimming and motor height can make a big difference to noise. Also gear/motor combo changes that speed up the cycle time seem to help - the noise might be the same in volume but occurs over a much shorter period so seems quieter. Obviously not much use if blasting away on auto though.
 
Of the group of people I Airsoft with, the quietest AEG is probably my brothers G36, maybe the polymer body helps? 
 

@Roryhas granted me the shoe in to think ‘outside the box’
 
The key thing is of course to have a safe environment, not break the law (proximity to footpaths and roads) and not annoy neighbours
 
If you want a fairly simple target then setup some simple targets to hit, add something ‘reactive’ such as metal that will pint (as per Rory’s can lid) or a soft thing such as paper that will show your hits
 
A novel option (which can work for airguns but may not work properly for airsoft) is to put paintballs on golf tees
For an airgun a good centre hit will burst the paintball, a glancing blow or whizz past might knock or blow it off
For airsoft I suspect a BB at any decent range may just knock down a paintball unless you had a good fresh tournament grade paintball 
But that does give a small target to try out your accuracy & your RIFs consistency 
 
 
If you’re a student or road worker then put some cones out 
However - be aware that hits will bounce away in various directions, so limited in where it would be suitable for garden targets 
Cones are great for an easily relocatable but solid target of varying size (not just that cones come in all sizes but you can aim for an easy shot at the lower wider bottom of the cone and work up to the slimmer top of the cone.  You can also pop a can on top or a stick through the cone holding up another target 
If you have a few cones then space them around at various distances and practice switching target 
Remember again that if you’re switching target then your hard backstop needs to cover the wider range of potential misses 

I like a wee garage pop when time allows. I get a robust cardboard box from the local supermarket and hang a bean tin lid from an old bit of wire. Can sometimes be a pain to maintain it "face on" if you use string but cheap and effective 


 

I have employed some former Conservative MPs to run around the garden while I shoot them; however, they seem to find it rather too enjoyable.

Paint can lids are my favourite. Make a mess but you know when you hit them.