A New Type of Airsoft System - Blank Cartridge Recoil Simulation

[PureSilver]

Hi all,
 
I've been thinking about a possible entry in the ACBC, and have alighted upon a slightly weird idea that I'm not sure anyone has ever tried before. Essentially, what I am considering is a spring-powered bolt-action rifle that also loads blank cartridges. When the trigger is pulled, the spring system launches the BB, and a separate firing pin ignites the blank cartridge, which produces the characteristic bang so lacking in spring rifles, and also diverts its gas into a recoil system for the kick also desperately lacking in such guns.
 
What's the Big Idea?
 
I want to produce a replica of a real weapon as a proof-of-concept of a system that uses blank cartridges to simulate blast and recoil (henceforth, Blank Cartridge Recoil Simulation or BCRS). For simplicity, I've chosen to replicate a bolt-action spring rifle, a weapon that suits BCRS well for its simplicity, compactness and low rate of fire. In particular, I've chosen Steyr's Scout, a weapon sadly not replicated so far by any airsoft manufacturer, for its magazine feed, internal volume, advanced looks, and aluminium/polymer construction:
 

 

What Does BCRS Do?

 

BCRS is intended to do two key things; first, it produces the sound of a gunshot to accompany the firing of the weapon, and second, it uses the gas produced by the blank cartridge to cycle a recoil system to produce a kick simulating the recoil of a real weapon.

 

How Does it Work?

 

BCRS is fundamentally a very simple system. It adds a blank cartridge system into the internals of the host weapon, effectively turning the airsoft gun into a blank gun and airsoft gun. The airsoft portion of the gun functions as normal, but it is linked to the blank cartridge system such that when the weapon is cycled both systems cycle simultaneously. Thus, when the weapon is cycled, the bolt will load a BB into the hop-up, and a blank cartridge into a second, separate chamber. When the trigger is pulled, the spring system will fire the BB down the barrel, and a striker will fire the blank cartridge into the recoil system. When the bolt is cycled again, it will eject the spent blank cartridge, and the cycle begins again.

Why a Bolt Action Springer?
 
The reasons for doing so are in my mind quite compelling. Regarding the bolt-action springer:

• The bolt-action springer is the most inherently accurate system in airsoft (with the possible exception of the Polar* Fusion Engine) for its consistency in any temperature.
• Bolt-action springers have additional benefits - they are mechanically very simple (compared to an AEG, GBB or Polar*) which makes them very reliable and quite cheap. Furthermore, they replicate the operation of a real firearm very closely, and can be designed to be compatible with real-steel accessories and parts (e.g. stocks, sights) without difficulty.
• However, their realism (and 'fun factor') falls down in two areas. First, like almost all airsoft guns, bolt-action springers do not make a convincing noise when fired; in fact, they are usually the quietest of all airsoft weapons. Second, like a good many airsoft guns, bolt-action springers (TM's rather weak RealShock system notwithstanding) do not recoil when fired. These are both advantages in competitive airsoft, but they're a huge shortcoming to the user experience otherwise. BCRS could address these two shortcomings by providing noise and recoil.

In particular with regard to BCRS:

1. The bolt-action springer is safe. The locking system of the bolt provides great strength and simplicity of design, reducing the risk and opportunity for failure that could injure me (during development) or, later, the shooter.
2. The bolt-action springer is not automatic. That means that I don't have to deal with the complexity of self-loading both a BB and a blank cartridge. It also means that I don't have to rely upon the recoil system for semi-automatic reloading, which could have consequences for the legality of the weapon as well as its reliability.
3. The bolt-action springer has a low rate of fire. That is useful because blanks are very expensive compared to BBs (at around £0.40 per 9mm blank, as opposed to £0.002 per 0.20g BB) and a weapon with a high rate of fire could prove too expensive to shoot. Furthermore, a low rate of fire restricts the amount of heat (produced by the blanks' deflagration) that can build up in the weapon; a weapon with a high rate of fire could become dangerously hot.

Why the Steyr Scout?

 

This weapon is intended to be a proof of concept, and possibly also serve as pattern for making more of these guns upon customer request. The Steyr Scout suits this aim because:

1. I only want to work on BCRS. Specifically, I don't want to work on stocks, bipods, rubberised grips et al. The Scout's stock is readily available from Steyr, authorised dealers and the second-hand market and should be easy enough to adapt.
2. The Steyr Scout is sold in the UK. I will need access to a real Scout in order to take measurements of all the parts that I can't legally purchase without a FAC. The Scout is sold in the UK, so I anticipate being able to gain access to one for measuring purposes.
3. The Scout's stock has spare internal volume. I anticipate the recoil system lying underneath the barrel of the rifle, and will require some space in which to fit it. The Scout's stock is fairly deep, so with luck everything can be packaged inside.
4. The Scout has an aluminium receiver. I will be having all the parts of the weapon that I can CNC machined. It's much cheaper to have aluminium machined than it is steel.
5. Real steel is king. Important parts of the real Scout that I intend to purchase - its stock, in particular - are not particularly expensive. The factory optic that it mounts (Leupold's FX-II Scout IER) is also relatively inexpensive.

On a more subjective level, I think the Scout looks cool, and given that no other airsoft replica exists, it will have rarity on its side too.

 

The Legality of BCRS:

 

BCRS weapons will fall under several classifications of UK law, being RIFs and blank-firing weapons. A great deal of the rules have identical requirements - blank firing weapons and RIFs cannot be sold to persons under 18, for example. Blank firing weapons are also subject to special rules regarding their ease of conversion to firing real cartridges. With the striker system being below the bore of the airsoft barrel, and no barrel being provided for the blank cartridge in the recoil system, I am confident that it would be nigh-on impossible to convert a BCRS gun to fire real ammunition.

 

Some Immediate Questions:

 

I can already hear some questions being asked, and hope to anticipate some of them:

1. Does the blank cartridge 'fire' the BB? No. No energy from the blank cartridge is transferred to the BB; the systems are entirely independent. In fact, the weapon will be capable of firing BBs when not loaded with blank cartridges.
2. Aren't blank cartridges dangerous at close range? In older barrel-venting blank firearms, yes, extremely. However, in line with current UK legislation, this weapon will not vent through the barrel but into an expansion chamber (to reduce pressure to a safe level) and then out of a vent in the forearm. It will do so through at a pressure and temperature that is 'skin safe'.
3. Aren't blank cartridges dangerously loud? Yes, particularly when you've got your head right next to them. At present, I'm not sure just how loud the gun will be when fired. All of the gas will have to travel through the recoil system, which will greatly attenuate the noise; similar containment systems form the foundation of several 'silent' pistols. It may be that certain sizes or types of blank cartridge are hearing safe and others are not; experimentation is the only way to be sure. It is my aim to produce a gun that is hearing safe not just for the shooter but for everyone else.
4. What sort of blanks will it use? It depends upon how much energy I can extract. At present, I anticipate that .22 blanks won't produce the necessary recoil; in addition, .22 blanks are rimmed and thus very difficult to stack in a magazine. I hope that the Steyr will fire 9mm blanks (which are conveniently rimless and common to BFGs) but if they prove excessively powerful I might substitute smaller rimless cartridges instead.
5. Will this be allowed at skirmishes? That will depend upon the site. Most sites already allow blank cartridges up to 9mm in BFGs, so in principal I don't see a problem. However, the gun will be capable of firing BBs when not loaded with blank cartridges, so if a site doesn't like BCRS you can simply not load the cartridges.

So? Is anyone else interested to see how this would turn out? Got any advice for me?

[Im going space]

this is a wierd yet brilliant idea and i wish you all the best in making it! it would be interesting as 90% of airsofters associate the noise of a 9mm blank with grenades so that may be an issue from the gameplay POV. but, as a technical exercise ect. brilliant.

[hotelkilo]

" I am confident that it would be nigh-on impossible to convert a BCRS gun to fire real ammunition"

 

this is what will cause u the most concerns imo, as almost anything can be converted to fire real ammunition (even if just 1 round)

 

also the 9mm blanks that bfgs use tend to the the rimmed 9mm blank also known as .380 blanks, they are more like a shorter .38 special than a true 9x19

 

perhaps the common 8mm semi-auto would be powerful anough for your purposes.

 

good luck, its certainly a good idea thats deserves further exploration, but i fear u will run afoul of the law before u get to production.

[bankz5152]

This is amazingly cool

[Tw1tch]

I am incredibly interested in your project here, something a little crazy but in a good way.

 

Best of luck!

[loki7491]

Wow... simply wow!

 

Best of luck and i wish you all the success you can have.

 

(I'll have a .303 No.4 if it all works out for you!)

[PureSilver]

" I am confident that it would be nigh-on impossible to convert a BCRS gun to fire real ammunition"

 

this is what will cause u the most concerns imo, as almost anything can be converted to fire real ammunition (even if just 1 round)

 

Yep, I reckon so. The bit of the gun behind the barrel with be mostly VSR-compatible stuff (why reinvent the wheel) so I don't foresee problems there; there won't be a striker lined up with the barrel either. The striker for the blanks will be low down in the receiver and not located behind any barrel; I think one-piece construction with the recoil sub-system should make it impossible to turn it into a firing weapon within the meaning of the relevant Acts. I'll probably knock one up, and ask my local Firearms Enquiry Team to look it over.

 

also the 9mm blanks that bfgs use tend to the the rimmed 9mm blank also known as .380 blanks, they are more like a shorter .38 special than a true 9x19

 

That IS worth knowing, thankyou. I shan't feel constrained to 9mm then, as you'll be buying a different tin of blank cartridges no matter what I use as you just can't stack rimmed cartridges. I reckon my choices are 9mm Parabellum and 8mm. Hopefully those aren't too powerful. If they aren't powerful enough (which is unlikely) there are industrial blanks for nailguns which will definitely do the trick.

 

Thanks for your support, everyone. I shall investigate further, and see if we can't make this happen.

[Im going space]

yeah '9mm' BFGs are actually .380 blanks

[jal3]

http://simunition.com/upload/documents/doc_95.pdf

[Im going space]

http://simunition.com/upload/documents/doc_95.pdf

funny you should mention that as i have two of the 9mms sat here that got caught up in my kit when i went to the RAF Heyford opening day

[PureSilver]

http://simunition.com/upload/documents/doc_95.pdf

 

Those things are seriously expensive, and you need special protection, and you have to use them with specific guns. Sadly not really airsoft compatible.

[renegadecow]

Brilliant! I'm thinking though that maybe even just .22 blanks can deliver a sufficient amount of recoil. On a real firearm or blank firer, it's not much, but you're putting it in a closed system pushing a weighted piston. Instead of relying on what energy the muzzle is able to deliver to generate recoil, a closed system is much more efficient. I'm thinking the difference between a firecracker ignited in the open and one in a bucket of water.

[heroshark]

theres always 22longs almost as loud as a 9mm

[PureSilver]

Brilliant! I'm thinking though that maybe even just .22 blanks can deliver a sufficient amount of recoil. On a real firearm or blank firer, it's not much, but you're putting it in a closed system pushing a weighted piston. Instead of relying on what energy the muzzle is able to deliver to generate recoil, a closed system is much more efficient.

 

I had thought about the big pressure advantage posed by the closed system with its small internal volume (as opposed to the increasing volume of a barrel with a bullet travelling down it) but I also thought that blank cartridges might well not have much (if any) of a powder charge behind them. A .22 which is basically just a primer wouldn't be able to generate much kick, although .22L or LR might be different stories. I suppose I'll have to get a fixture machined up and get some testing done.

 

Incidentally, since you seem to have grasped the recoil system perfectly (even from my description) how do you think the piston should return? What I figured was the gas would push the piston (the weight, essentially) towards the muzzle of the rifle (creating the recoil). When the piston reached the end of the cylinder it would expose a port to vent the gas pressure. That's necessary firstly to reduce the pressure to a safe level before the spent cartridge is extracted (we don't want it firing back at the shooter!) and secondly to provide a clean supply of oxygen for the deflagration of the next cartridge.

 

The question is, how best to bring the piston back to its starting position? You could have it sprung, but then it would return before the pressure had equalised and I think it would make the recoil feel weird, jumping first one way and then the other. You could have it drawn back with the bolt, but that (plus some heavy springs) might make the bolt pull very heavy. My favoured solution is having it weakly sprung and caught by a catch at the extreme end of the cylinder (much like any semiautomatic sear), which would require only minimal force on the bolt pull to uncatch ready for the next shot.

[hwagan]

Incidentally, since you seem to have grasped the recoil system perfectly (even from my description) how do you think the piston should return? What I figured was the gas would push the piston (the weight, essentially) towards the muzzle of the rifle (creating the recoil). 

 

 

This seems like an awesome idea, and I wish you all the best with the build - Although wouldn't it make more sense to have the piston travelling towards the rear of the rifle rather than the muzzle so the impulse is going in the correct direction? 

[jal3]

Those things are seriously expensive, and you need special protection, and you have to use them with specific guns. Sadly not really airsoft compatible.

 

You're thinking of the marking ammunition.

I linked the non-marking version.

[PureSilver]

wouldn't it make more sense to have the piston travelling towards the rear of the rifle rather than the muzzle so the impulse is going in the correct direction? 

 

You might be right. My thinking is that the recoil of a real gun is the equal and opposite reaction of the bullet being launched fowards up the barrel, causing the gun to jump backwards. If the charge were to push the weight (the 'projectile') backwards, wouldn't the gun jump forwards? There's definitely an issue where the piston slams into the end of the cylinder (pulling the gun forwards). I guess we have two ways of simulating recoil:

• The way a real gun does it - by launching the piston forwards. This acceleration pushes the rest of the gun back. However, when the piston hits the end of the cylinder, it will pull the gun forwards as it imparts its energy to it. There are a few solutions to that problem - one would be a series of sequential vents rather than just one (reducing the pressure as the piston travels up the cylinder until it runs out of energy before hitting the end of the cylinder). Another (possibly in combination) would be a weak spring at the end of the cylinder, which would slow the piston and muffle the energy transfer.
• The way GBBrs do it - by launching the piston backwards. This acceleration pulls the gun forwards but the travel is so short that the collision with the end of the cylinder is almost immediate, pulling the gun backwards. This would cause some rather awkward packaging issues - if the cartridges were coming from the magazine, the recoil system would have to be behind that (and thus in the pistol-grip area of the stock) which would be a challenge.

Ideas, anyone? You can see that G&G's recoil G96 does it the second way:

 

 

You're thinking of the marking ammunition.

I linked the non-marking version.

 

Am I? Non-marking or not, it's still a projectile being launched explosively which is pretty much the definition of a regular firearm. The linked leaflet says that it is to be "Used with FX^® protective equipment including mandatory head, throat and groin protection" so it clearly is still a bit dangerous. I agree that airsoft (at least bolt-action rifles) needs to revisit rifled barrels and spin-stabilized projectiles, but I had Asahi's Blade Bullets in mind, not powder-charged Simunition (which, BTW, non-marking or not, is AFAIK still brutally expensive compared even to regular ammunition).

[Beeingmyself]

Interesting idea but

 

Cost of gun

cost of casings

Custom clearace due to most countries where airsoft is popular RS is very restricted.

Silenced sniper with only the recoil versions.

[renegadecow]

Recoil can be touchy when talking airsoft. On most GBBs and GBBRs the felt recoil is more pronounced by the oscillating weight of the slide or bolt rather than the actual slamming of parts. With something like your system you could drive the piston straight into the shooters shoulder making the impact what's felt. I'm thinking a relatively light weight piston with hardened ends on a soft return spring. The piston is driven by exiting gas and slams towards the shooters shoulder. Towards the end of the cylinder the piston rides in, it has sufficient vents to bleed excess pressure so by the time the piston hits home it's just inertia pushing it and not the gas anymore (in case excess gas drives the piston too hard and breaks something). What's harder to consider is how the blanks will feed and eject and if they'll be stored in a separate magazine from the bbs.

[PureSilver]

With something like your system you could drive the piston straight into the shooters shoulder making the impact what's felt. [...] What's harder to consider is how the blanks will feed and eject and if they'll be stored in a separate magazine from the bbs.

 

The blank cartridge/BB feed issue is an interesting one. The first thing to note is that it would be conceptually desirable to have them feed from the same magazine, because:

• That way you only have to remove one magazine and cycle the bolt to make sure that the weapon is unloaded.
• When reloading the weapon in the field, you don't have to fiddle with two magazines.
• You can make sure that there is always a congruent number of blank cartridges and BBs in the magazine.

The second thing is that it's going to be very difficult to do that. Where I can put the recoil system in the gun is constrained in a number of ways:

• If the shells are to be ejected from the breech, the recoil system's chamber and firing mechanism must be below the breech. However, that's precisely where the magazine normally sits. There is an extended magazine assembly which could lower the entire magazine (making space for the recoil system) but it's pretty ugly.
• The recoil system will be physically relatively large in order to have a decent amount of weight in it. Since the butt of the Steyr is partly hollow, the only real place to the system is in the forearm of the stock.

The kick of the real .308 Steyr Scout (the one I would replicate) has helpfully been calculated by a fairly committed owner at a velocity of 12.4f/s and 16.6ft lb of energy with standard 150gr bullets. I will have to do some bench tests in a fixture to determine exactly how much energy one can extract from various blank cartridges, and work out from there exactly what sort of masses would be necessary to achieve felt recoil in the same order of magnitude. I don't want it to kick as hard as the real thing - that would be painful after a day's skirmish - but I don't want to go to all the trouble of cartridge-based recoil for the same effect as a decent GBBr.

[jal3]

 Am I? Non-marking or not, it's still a projectile being launched explosively which is pretty much the definition of a regular firearm. The linked leaflet says that it is to be "Used with FX^® protective equipment including mandatory head, throat and groin protection" so it clearly is still a bit dangerous. I agree that airsoft (at least bolt-action rifles) needs to revisit rifled barrels and spin-stabilized projectiles, but I had Asahi's Blade Bullets in mind, not powder-charged Simunition (which, BTW, non-marking or not, is AFAIK still brutally expensive compared even to regular ammunition).

Yes you are.

 

Look at the specs.

170m/s with a 0,11gr is 1,7j. It's not dangerous. Also the shell folds at the nose (this is how it normally spreads the marking payload).

Rifling/elongated projectiles in airsoft is a horrible idea unless you shoot insanely fast.

Everything's expensive...it's the price of performance

(And yes i've been hit by the marking ones, they hurt like hell. Then again, so does paintball ).

 

I'm not saying you should use simfx, but it's worth taking note of it and how it works. It produces low muzzle energy with high recoil from a single shell.

 

If it was me, i'd do either of the following.

A:

Let the gas from the .22 push forward a piston that pushes air into the barrel (basicly replace spring with .22).

B:

Let the gas from the .22 piston bleed into the barrel through a tiny hole.

 

The first one is probably the best, since it keeps fouling gas out of the barrel (a tiny vent hole would require cleaning often to give the same pressure/fps).

[scorch]

That's just a firearm then.

 

Albeit an indirect one like the Russian gas contained piston cartridges.

[renegadecow]

If it was me, i'd do either of the following.

A:

Let the gas from the .22 push forward a piston that pushes air into the barrel (basicly replace spring with .22).

B:

Let the gas from the .22 piston bleed into the barrel through a tiny hole.

Unfortunately that would make it a firearm in many places. Even if it's firing at airsoft levels propulsion is still indirectly caused by gun powder.

[PureSilver]

I'm not saying you should use simfx, but it's worth taking note of it and how it works. It produces low muzzle energy with high recoil from a single shell.

 

If it was me, i'd do either of the following. [...] Let the gas from the .22 push forward a piston that pushes air into the barrel (basicly replace spring with .22). [...] Let the gas from the .22 piston bleed into the barrel through a tiny hole.

 

Like I said, Simunition is a great idea provided:

1. You have the appropriate authority to own cartridge-fired firearms.
2. You have the money for the system.
3. Everyone else has both of those too.

Unfortunately, as the others point out...

 

That's just a firearm then.

 

...in most countries, using the energy from a cartridge in any way to propel a projectile is a firearm, not an airsoft gun. Therefore, the Simunition model of integrated cartridges is unfortunately legally prohibited from airsoft (which is good, because it would be an advantage limited to the very wealthy!) and not really applicable to this project. It's a shame, because ideally I would do exactly what you suggest - use the .22's energy to power the piston. That system would compensate for inconsistencies between cartridges, it would be very simple (simpler even than a regular springer!), robust and tunable. Unfortunately, it would also be very illegal in the UK.

 

Rifling/elongated projectiles in airsoft is a horrible idea unless you shoot insanely fast.

 

Now, what I'm basing this idea on is Asahi's M40 and their Blade Bullet design (fortuitously, a member of this very forum, wolfgeorge, owns one of the extant examples). That used finned projectiles and, AFAIK, a rifled barrel. Presumably it operated within the boundaries of JDM airsoft limits (i.e. 1J) but despite this is widely considered the most accurate airsoft gun ever made. I would LOVE to make an airsoft gun with the barrel from a .22 (5.56mm) air rifle and use appropriate ammunition, but that depends on ammunition manufacturers, not me. Since no-one in the entire air rifle world makes all-plastic pellets (that aren't just BBs), there's no ammunition for such a rifle to shoot.

 

[scorch]

Plus, in order to properly engage the rifling it needs to impart an awful lot of energy to the pellet to overcome the friction.

 

If you wanted to test the concept though, couldn't you try removing the metal tip from a plastic pellet? Perhaps a .177 in a .22 barrel would spin enough at airsoft velocities without all that friction?