Pseudotectonic

Amazingly the story of UKARA is truly becoming lost history because their operation is so obscure. Here is a brief mention of it being an Excel file sitting at a site called Ironfoot Airsoft that used to exist (near the GCHQ site), but the farmhouse is now demolished. So there is really no solid up-to-date information of exactly who and where and how UKARA is maintained.

In the spirit of larping we can actually wargame this out: In what circumstances would the VCRA be amended to not allow RIFs being sold to airsofters? (I'm surprised GPT actually came up with some half decent answer, for comprehensiveness I'm editing collating the key points below) Can you suggest actions airsofter can take to prevent these items This AI is not bad

This is going back to the discussion of having an association/federation/facebook group Who should be keeping track of and able to pull out numbers about the airsoft economy

Melamine foam (aka magic erasers) might be a good alternate It has rather high NRC and is also in some brands of acoustic panels With PU foam there are many grades and weights and whatnot and not every type is good for absorbing sound (some are), whereas melamine foam seems to outperform even the acoustic grade PU foams especially towards the higher frequencies, which is what we want Magic erasers are rather cheap and easily available, and it is safe to handle and very easy to cut to shape, just get a pack and cut out some round sections and stack them You can even scrub dishes with it

The more I think about it the more I feel air diffusion does not really matter, because the air pocket will seek the path of least resistance and this will be around the BB and in front of it. When the BB is just entering the suppressor, the clearance will allow the air to go around and this inrush pressure will hammer on the first few mm of material around the barrel exit, but will quickly diminish as the air go around and in front of the BB, rather than hanging around looking for openings in the foam/mesh/wadding. This will have already finished happening before the BB is even a few mm into the suppressor. Therefore the fill material does not really need to diffuse any air, its only job would be simply to absorb the shockwave, but not necessarily absorb any air volumetrically. Therefore it can be a solid material. Now in order to absorb the shockwave and not echo or transmit or reverberate it, it needs to be somewhat flexible I suppose. If one were to isolate this shockwave in audio it will probably sound like a high pitched crack, because it is essentially a sharp hiss of air that is compressed into a very short time, it will be in the upper frequencies because dimensionally and energetically it should not produce any component in the lower frequencies. What fill material (at 10-12 mm thickness) is best for muffling high pitched noise (say 2 kHz to 20 kHz)? If we go by this chart we may be looking at some sort of "fiberglass board" or "sprayed cellulose fiber" (look for a high Noise Reduction Coefficient at high frequency ranges) Now we don't want to be blowing fibreglass particles around so we can rule that out Cellulose on the other hand seems to be the best material for the job but might be impossible to put into a can and keep it there (not to be confused with spray foam) So the key might be instead finding something that has the next highest NRC, perhaps carpet tiles

oh nonono SHS_hightorque_is_not_hightorque.png SHS high torque is 16 TPA, it is low torque Get a 22 TPA if you can, and when you are ready pop a 13:1 in there, or better yet a Perun Hybrid and turn on precocking

https://www.burymercury.co.uk/news/24345047.second-report-weapon-seen-bury-st-edmunds-town-centre/ "air-powered ball-bearing weapons" why do people always come up with new nicknames for airsoft

If the 25 days are well paid like a proper summer job then I can see people volunteering, otherwise they'd think it's authoritarian being forced to working for free when the economy is beyond fucked up

Let's do some maths Let's say we want to completely contain the pressure wave within the can so by the time the BB exits there is zero difference in air pressure inside and outside the can, meaning the ideal air volume in the can plus the volume of the barrel should roughly equal cylinder volume: Vcan + Vbarrel = Vcylinder The typical cylinder volume is what, ⌀ 24 mm x 50 mm? or ~22.62 cm3, if this is 3/4 ported it becomes ~17 cm3 If my barrel is a 270 mm barrel, ⌀ 6 mm x 270 mm is about 7.63 cm3 (so the ratio is about 2.23 it seems but this is irrelevant) That gives me about say 9.4 cm3 of air that needs to be diffused inside the can Assume we are using a replica of a 556 can with an external size of say ⌀ 38 mm x 157 mm, subtracting the body thickness and a layer of butyl tape lining of say 2 mm and fittings etc we have an internal volume of say ⌀ 32 mm x 110 mm or thereabout or 88.47 cm3 of total space inside Of course we need to leave a clear corridor for the BB to go though and it cannot be so tight, if it is ⌀ 10 mm x 110 mm this is 8.64 cm3 out of the 88.47 cm3 that needs to be kept clear, giving us say 80 cm3 of diffusion zone available But this BB clear corridor should also be included in the Vcan so this ⌀ 10 mm x 157 mm or 12.33 cm3 is already bigger than the 9.4 cm3 volume we need to normalise That means, the foam fill material within the 80 cm3 diffusion zone is really just handling impulse pressures And if we sketch out the wavefronts we can see most pressure is probably in the beginning 1/3 portion of the can, accordingly we can use a dense mesh here, and use a more open mesh in the later 2/3

Nah if it works, it works, but if it happens to get hot during the game, you know why

PME means pre-mature engagement, that is when your ROF approaches about 30, your sector gear will be too fast and will try to engage the piston while it is still travelling forward i.e. the sector will slam into the middle of the piston rack and chewing up gear teeth Since SHS "high torque" is actually a 16 TPA high speed, I think with 11.1 and 13:1 gears it will probably go over 30 RPS, hence the PME risks

Good point about gradual reduce of the pop, so perhaps the whole thing should be filled with some sort of open cell foam that is high enough porosity for maximum diffusion So perhaps there is some merit about the common paint roller insert Butyl I guess is nice as a middle damping layer between materials, or a lining layer, but not sure if it is the best interface for the air borne noise, because maybe the smooth surface isn't as good as an open cell structure for diffusion of the pop Maybe if you roll up some thin gauge wire mesh to simulate an open cell structure it would be very effective at diffusion and absorption?

Oh no not another, SHS high torque is not high torque But yours sounds nice But don't be tempted to go 11.1 with this, you will get PME

Just theorycrafting here... just a sketch to note down what we have to deal with... 1. Vibration damping: We know the case will resonate and vibrate from any sound from inside (air expansion) and from the barrel (piston impulse) so the case need to be treated to become a composite material so any vibration is deadened rather than resonate, can be achieved with a lining of vibration damping tape or with similar principle 2. Air gap: To limit energy transfer from inside to the case, maybe we can leave an air gap so all the air expansion is contained and processed inside, rather than transferred outside to the case 3. Absorbent material: We need to convert as much sound into kinetic energy as possible at this layer, maybe a heavy and absorbent material, maybe some sort of rubber or silicone or something along those lines 4. Air expansion chamber to match the cylinder volume ~1:1 so the space can be filled with as much absorbent material as possible (for the highest conversion ratio possible), geometry to match the air expansion pattern, and/or optimised for absorption (depending on how the absorbent layer is made). This area probably needs to be towards the back. 5. The "exit tunnel" of the BB should be towards the front so any leftover sound from the air expansion zone can be limited, we just want the BB going out but with minimal air pressure i.e. sound. TLDR we need to convert the vibrations into heat as much as possible, and we try to do this inside while limiting any transfer to the outside

I wonder if you roll up enough kitchen foil so it becomes a semi-solid aluminium block (with just the middle part hollow where the BB passes through) would it be effective because of the mass

How do you get a specific size thin wall stainless tubing? from a sheet/foil? And how do you keep it in place?

@ParHunter The clearance between inner barrel and outer barrel is probably too small (in mine it was ~0.3 mm diameter difference / 2 = 0.15 mm) for o-rings, plus it is meant to slide horizontally and having o-rings can introduce friction which hinders the magazine insertion, because your barrel would behave like a piston and will require more force to slide it (from the magazine pushing the hop unit as it is being inserted) And if you have o-rings you will need to machine some grooves on both parts to keep them in place, and then you will have a new compatibility issue with aftermarket barrels etc

You need to narrow down where your leak is For example you just compress the piston with cylinder with your palm, and then add the cylinder head and try again, and then add the nozzle and try again Then you will know which part is leaking more or less

@Cannonfodder Certainly importing is a VCRA s36 offence for "Manufacture, import and sale of realistic imitation firearms", which allows for a few defences including historical re-enactment and airsoft skirmishing It is the exact same offence when someone sells an RIF @JinxDuh Unfortunately disabling it won't be relevant for the purpose of VCRA, because an RIF is purely based on appearance However you can two-tone it, or make it entirely a certain bright colour, it would become an IF and no longer subject to s36

Are you sure it was the police who called you, and not the customs?

Those are RIFs. There is no UK law against export of RIFs. (Not sure about any import law on the other side) It is only when you bring them back i.e. importing RIFs it becomes a VCRA offence. Among the available defences, in your case it would be the defence of holding of organisation and holding of historical re-enactments. You just need some evidence for it e.g. photos from the event, and there is no sign of you doing anything not allowed.

... they are probably chronoing it. I think they will see that it is just a genuine mistake and might try their best to let it slide, e.g. dial up the hop up and using different weight or brand BBs so it passes chrono without them having to do any more paperwork. I am just guessing of course.

https://www.cps.gov.uk/legal-guidance/firearms#a03 I don't think you need to worry too much, especially if it hasn't even found its way to you yet. Given it is just a small technical contravention (an 8% is arguably within margin of error) they might let it slide, or just seize it and then give you a talking and ask for your UKARA just to make sure. But how would they even know the joules? They wouldn't know unless your RIF declaration form says it is over 1.3J and raising a flag...

try this

I think the barrel is a 14.5" so if you have to choose between 12" or 10", I think a 12" would be more appropriate For reference the URGI handguard is 13.5" The DD RIS II is 12.25"