A New Type of Airsoft System - Blank Cartridge Recoil Simulation

[jal3]

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.

 

Hmmm.

What's the point of installing an airgun barrel in an airsoft gun? Wouldn't it just be easier to weaken the spring in the airgun...oh well.

 

You could always have the ammo made if it was such an important thing.

 

The reason long projectiles are bad is that you can't apply hopup. Because of this thing called gravity, bullets will fall when you fire them.

The trick is to reach the target before the projectile falls too much to be feasable. Hopup, counteracting this effect, is great for range with slow moving projectiles.

 

If you want to really shoot far, try modding a smoothbore 4,5mm airgun to have hopup. At M210 0,35gr, it reaches 80m before it's down to 1J... Ammo is right there; high quality steel bearing balls. (And you should of course also tune down the spring)

[bankz5152]

Thats some good info mate.

 

I may try fitting a hop unitnto my air rifle

 

Sent from my GT-I9300 using Tapatalk 2

 

 

[PureSilver]

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?

 

Well, if it doesn't engage the rifling, it won't spin - and without spin, what's the point? That's the problem with testing .177s in .22 barrels (or .22s in a 6mm barrel). There's no problem with imparting a lot of energy to the round so long as it doesn't have too much energy when it exits the barrel, so I don't see a problem (in theory) with a gun that puts a 0.25g slug downrange at (say) 400fps. Pulling the metal tip from plastic pellets won't work - they need the mass for stability, and the point for aerodynamics.

 

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.

 

Point taken - but like I'm saying, the way it does that (using the cartridge to impart energy to the projectile) is illegal for airsoft use in the UK. In fact, the single shell idea is itself illegal in the UK (as a 'self-contained cartridge system') even when it's air rather than gunpowder in the cartridge.

 

What's the point of installing an airgun barrel in an airsoft gun? Wouldn't it just be easier to weaken the spring in the airgun...

 

Airguns in Britain are specifically designed not to resemble RIFs. I concede that you'd probably be taking more from the airgun (barrel, operating mechanism, magazine parts) than from the airsoft gun (stock, receiver, trigger mechanism etc) but like the Steyr, I'd rather have a conversion kit that fits RS parts.

 

You could always have the ammo made if it was such an important thing.

 

I wish. To get a decent ammunition manufacturer on board (e.g. BB B******, one of the smaller and Western manufacturers) I'm guessing I'd need an order in the hundreds of thousands/millions. That's a lot of ammo for the development stage when I won't know what exactly the tolerances and shapes should be, let alone the weights. If Asahi hadn't discontinued the Blade Bullet along with the M40 this would be a different story.

 

The reason long projectiles are bad is that you can't apply hopup. Because of this thing called gravity, bullets will fall when you fire them. [...] The trick is to reach the target before the projectile falls too much to be feasable. Hopup, counteracting this effect, is great for range with slow moving projectiles.

 

Without being unduly blunt, I am familiar with the operation of hop-up. I also know that real firearms don't have hop-up - they have rifling - and it seems to work OK for them. I also know that even at airsoft-level velocities the Asahi M40, with its rifled barrel and fin-stabilized ammunition, worked considerably better than any contemporary hop-up system (indeed, perhaps better than any comparable hop-up system period.) If Asahi's sytem had had the chance to benefit from two decades of extra development (like the hop-up unit has) I think it's a reasonable assumption that it would be certainly the equal of any hop-up unit made today.

 

If you want to really shoot far, try modding a smoothbore 4,5mm airgun to have hopup. At M210 0,35gr, it reaches 80m before it's down to 1J... Ammo is right there; high quality steel bearing balls.

 

Steel BBs aren't site legal anywhere I know of in the UK.

[scorch]

I dunno, I reckon it'd engage to a minor extent. I just tried dropping a .177 down a .22 barrel and it did touch the sides and stop. You won't need a massive amount of engagement at low velocities.

 

But if they're too light and the aerodynamics are too poor then it's a moot point anyway.

[PureSilver]

What we really need is wolfgeorge. Paging Dr. Wolfgeorge...

[Dr.Arnie]

Hmm, interesting idea but I can tell you now that using 9mm blanks is out in this set up and dangerous without a way to cent the gasses quickly. If any one has used a hilti gun you'll know that a .22 blank round is enough thrive a nail through anything, I used mid powered cartridges to fire nails Into reinforced concrete soba 9mm is ott. If you don't give it sufficient venting, and I can't see where you could without damaging the users hands or the barrel, then you will have a bomb on your hands. .22 will be more than enough if you want to go down this route but I would advise against it all together.

 

I do airsoft for *suitcases* and giggles, and personally don't mind about recoil so long as my gun works. I know there's are different though.

 

Why don't you just use a 12g co2 bulb and valve set up to give you recoil, it's a lot safer and you'd avoid all the red tape. You'd loose the noise effect but IMHO it would be better.

[PureSilver]

To be honest using cartridges of any sort is dangerous without a way to vent the gases safely, but that doesn't hold back blank-firers in general (or BFGs in particular, to use an airsoft example) so I don't see it as a particularly difficult problem, let alone an insoluble one. Blank-cartridge-firing semi-automatics use a much more complex and dangerous system than a bolt-action rifle, and they're cheaply made of nasty materials, but I don't think people are always worrying they're going to blow their hands off. If you were wondering, the gas system in the Scout would vent from the fore-end of the stock, probably from a port below the barrel, and only after a large expansion chamber to reduce pressure and temperature of the exhaust to a safe level.

 

The first thing to say is that this is a problem of design philosophy more than anything; safe design does not necessarily cost any more than unsafe design. I would work on this the same methodical way anyone working with pressurised gases would; first, working out the maximum working pressures developed by the blanks, designing accordingly with an appropriate safety margin, subjecting the designs to FEA, modify accordingly, destructively test, refine, etcetera. The gun needs a fail-safe design that renders it as safe as possible in the case of catastrophic failure, but that's not especially complex in the bolt-action Scout. BCRS does take these concerns into account; I don't want to lose a finger or eye any more than you do. Any production weapon would be proofed the same as any other cartridge-firing design.

 

The second thing to say is that the 9mm blanks used in Hilti direct-fire and contained-piston designs aren't the same as regular blanks, being designed to higher operating pressures, but they are usefully designed to use the 'work' of the gases and they are encouraging. If you can use them to power a nailgun, you can certainly use them to generate recoil. They do present a problem (though not an insurmountable one) of how to protect the stupid shooter from himself when he tries to load overpowered (or even real) cartridges into a BCRS gun. Like I said, designing the gun not to accept such cartridges, and to break in a contained fashion, is far from impossible.

 

In terms of what blanks I'd like to use, I'd like to use .22s. They are very cheap, they are very compact (which is important when I have only half as much magazine space to work with in the Scout as the RS does), they're more likely to be hearing-safe, and rimfire ignition is easier to work into my conceptual bolt arrangement than centrefire. The only reason for using more powerful cartridges is if .22s don't have the necessary power, and at present it's beyond my design capabilities to forecast exactly how much 'felt' recoil I could extract from the various alternatives.

 

Sadly until I've got some money (or a generous machinist - Docmv400, 

) for test fixtures to explore potential recoil system arrangements, this design exercise will have to stay on the drawing board. If anyone reading this has a particular firearm they'd like to sponsor, drop me a PM - I think the SMLE would be perfect...

[Bane]

I believe i could be of some help..

At my previous job one of the products we manufactured were certain devices referred to as "Cattle Killing Guns" These weren't so much a "Gun" as they were a trapped bolt inside a piston arrangement, a .22 blank was fired, driving the piston through the animals skull to euthanize it humanely (Still current practice strangely)
 

 

Now this is valid, because we used to stuff around with these ALL. THE. TIME. There was *NOTHING* we didnt fire/destroy with one. And the system is very similar to what you are describing.

Apple ontop, dissapeared spraying everybody in the vicinity with applesauce
Golf ball- dissapeared straight up never to be seen again

Punched holes through a phonebook.

Etc etc.

 

These gave off a considerable amount of recoil, but the main engineering issue we had was the built up energy in the system.

 

Our first prototypes smashed the front of the bolt assembly off due to the captured Piston/Bolt system. It was OK for maybe ten or twenty shots, but after a while the metal fatigued due to being slammed so hard. We had to beef it up considerably, increasing a 3/4" shoulder to 1" thick and a bit bigger than 1/4" piston wall thickness to just under 1/2"

This made the entire assembly exeptionally heavy. Yet, i still managed to break several bones in my hand and wrist and have the gun dissapear through the roof after we tried to explode an Orange on the workbench. The piston hit the bench. This was a quick lesson in just how much stored energy these things have.

Even for a .22 they have *ALOT* Of power behind them. Do *NOT* Underestimate and be EXTREMELY Careful.

 

Anybody who's ever used an old J-22 ramset gun and had a nail stick on them can attest that they can throw you around.

 

With that in mind. Here's some data for you from my books.

 

 

.22LR Blank produces 22,000-25,000 PSI, this number can vary, but note that they CANNOT POSSIBLY EXCEED 25,000 PSI for standard .22LR style Blanks. 
To be considered "Safe" The system must SUCCESSFULLY pass a Destruction Test and remain FUNCTIONAL at a 35,000 (Or 40,000) PSI overload. (Old data, will dig out my new SAAMI spec standards and correct this)

 

 

The main issue in my mind is creating a piston-recoil-simulation system that wont blast any recoil mechanism back into the operator's face in the event of a catastrophic failure. I would suggest having any and all moving parts moving in the direction away from the operator, in a better-safe-than-sorry mentality.

As for practicality, i wouldn't say it is, in the slightest. 

But, i'd like to see you manage it. Even with C02 which would be MUCH Easier to manage/control/build/more legal

[PureSilver]

Ah-hah! Just the sort of experience and numbers I need. If you've got the newer SAAMI data, I would much appreciate it. Do you have any photos/engineering drawings of your boltguns?

 

[EDIT]I've come to the conclusion that you might literally be God-sent. After looking at captive bolt pistol designs for the last half-hour, I can see the similarities (and the differences) quite clearly. The most basic information - how thick your breech and cylinder needed to be, all that - is absolutely amazing, thank you. I otherwise have absolutely no idea where even to start when it comes to dimensions and the like. (Oh - and don't worry - you aren't going to get me killed by giving me this information, I'm nowhere near the test fixture stage.) The big thing I want to say is that my system will bleed the gas off into exhaust ports as testing proves necessary - probably in the testing phase with multiple adjustable jets arranged down the cylinder - so that there won't be the built-up energy towards the end of the cycle that I think you're describing. The system will need to be tuned according to the size and spacing of those jets to achieve the desired 'kick' of recoil. How did your design vent after the cycle was completed?

 

It's also very helpful to have some ideas of the SAAMI pressures of the .22LR blanks. There are of course even lower-power alternatives (.22 Short) but I really don't think they'll be necessary. I think there are some critical design factors I can take advantage of compared to your captive guns (like increasing the internal volume of the recoil system compared with the VERY small internal volume of a captive bolt pistol to reduce the internal energy, venting gas immediately, etc) to reduce the overall stresses and pressures. If this thing is ever to be built, I will of course have it proofed to the appropriate level.

 

In terms of failsafe design, you're absolutely on the money when it comes to have the moving parts moving away from the operator - that's the plan I was going with anyway, with the piston moving towards the muzzle of the weapon.

 

Testing is what I need. I don't suppose you still work in an engineering capacity?[/EDIT]

[mattmanic]

Have you considered using Nitrous Oxide bulbs instead of CO2 for more pressure? I may be missing the point...

[renegadecow]

NO2? People will start rummaging in your kit when you're not looking to huff on the stuff. At least, I know I would.

[PureSilver]

Right, after poking around on SAAMI's website for a while, I've been hunting the information I need to make a test fixture chambered for the various .22 blank cartridges. Starting with the breech, SAAMI very helpfully provide a set of dimensions for .22LR (the parent case of which, .22 Long, is the longest .22 blank case around, and therefore the longest cartridge I need to be able to accommodate). Their technical drawing is quite informative:
 

 
Now, of that diagram (apologies for the Paint annotations, click through for original resolution):
 

 
You can see that the chamber can be greatly simplified because the test fixture can dispense with the tapering of the throat of the chamber (to engage the bullet with the rifling) and with the rifling itself. The question I don't immediately have an answer for is to what extent the head of the blank needs to be supported. In a cartridge with a bullet, the support offered to the forward edge of the case by the breech (the 'headspace') is critical; without sufficient support, cartridges can suffer catastrophic failure:
 

When a firearm has more headspace than the cartridge design anticipated, the closing of the bolt or impact of the firing pin may move the cartridge forward to leave space between the chamber face of the action and the base of the cartridge. Pressure of burning powder gasses expands the thinner forward walls of the cartridge case to firmly grip against the sides of the chamber preventing rearward motion. The thicker base of the cartridge case (or sometimes the primer) may then be forced back into available space at the rear of the chamber, causing the case to stretch. [T]he primer may rupture or the base of the cartridge case may begin to separate from the forward walls. Either type of failure may release high pressure gas and case fragments from the action of the firearm.

 
How a cartridge is headspaced depends upon its design, which determines the datum point from which headspace is measured. For example, using a drawing of Russian 7.62x39mm;
 

 
A cartridge could be headspaced to the case mouth (L3), like .45ACP, to the shoulder of the cartridge (L1, L2, or somewhere in between) or to the rim at the base of the cartridge. Rimmed cartridges like the .22LR are headspaced from the rim, to allow weapons to shoot multiple cartridges of the same calibre (e.g. .22CB, .22 Short, .22 Long and .22LR) from the same chamber - which is exactly what I want to do with the test fixture. It seems logical that the head of the cartridge does not need to be supported - the crimped blank simply opens up - but I'm not 100% sure. Can anyone confirm that?

[T3CH]

You do realize if you progress past theory you are committing a crime right?

 

Manufacturing a firearm to be specific.

[PureSilver]

Sigh. Did you read any of the above thread?

[renegadecow]

He isn't as the projectile will not be powered by the blank but of its own independent spring system.

 

@PureSilver

I can't find my "empty" 9mm blank right now, but my .223 one remains crimped after being fired. The headspace does not need to be supported, but in the case of the bottle necked cartridge, needs that bottle neck to keep it from moving too far forward out of reach of the firing pin. On the 9mm, it has a ledge at end of the case to seat against the chamber. They're not actually made from 9mm brass but something longer with the bullet still being part of the case.

 

edit:

As you'll be working with .22s you don't need to worry about that with them being rimmed.

[PureSilver]

That is exactly the answer I wanted, cheers RC. I've been looking at photos of expended .22 Long blanks and most have only partially uncrimped. I'm getting the impression that what I need to do is leave enough chamber to support the blank and the potential expansion of its crimp, and then have sufficient travel in the ejection cycle to remove a case that has come uncrimped (and therefore become fractionally longer).

[BaBaBooey]

I apologize, I didn't read every post, but Kokusai made something very similar in the early 80's that you might want to look into.

 

One of my first airsoft gun was a Kokusai M700BDL using their "Super Weapon" design first released in 1984. It basically has a separate BB firing air mechanism combined with a model gun mechanism that used 7mm PFC's. They also released a semi only M16A1 and XM177 using the same principle, and select fire versions a few years later.

 

On the M16, you would actually load the BB's into a small slot in the charging handle and the BB was shot through what would be the gas tube on the real gun. There is a small opening on the front sight base that the BB would shoot out from. The blowback from the PFC action would chamber the next BB and push the air cylinder back. The M700 worked similarly, but a bit more realistic since no blowback action is needed. The BB's are loaded into a small opening on the front end of the stock. You would load PFC shells with 7mm caps similar to the real gun.

 

7mm caps are no where near as loud as a real gun, but it's fun to shoot as there is a fairly loud pop combined with a quick flash and smoke around the chamber (more noticeable indoors or at night). Also, the performance compared to today's air rilfes was poor (no hop up, etc).

[PureSilver]

Ah, very interesting! The guns and my system aren't quite the same - the M700BDL appears to use the PFCs just for noise, not recoil, correct? I'm not sure I understand how the semi-automatic AR-15s worked. Did they use the blowback from the PFC to cock a springer piston, or did the PFC fire the piston as well as cycle the bolt? It doesn't sound like they're a very good design (from what little I can find on Google, the entire BB system appears to be mostly in the front handguard, and shooting the BB through the gas tube is frankly silly, though I can understand why they had to) but they do sound very interesting. The idea of using the energy of the blank (or, in this case, the PFC, which amounts to the same thing) to cycle a springer system and a recoil system is VERY attractive. That would give you all the awesome advantages of a springer - simplicity, total independence from batteries and gas, unaffected by temperature - and none of the disadvantages of low rates of fire, etc. There are some pretty significant problems I could foresee from heat build up, and of course the cost of a 30rd magazine would be almost fifty times what it would be with BBs alone (around £3.60 per mag, if you're using .22LR blanks) but God it would be awesome. The question then depends on the legality, which I think could be tricky, as you are (however indirectly) using the energy of the cartridge to shoot the BB.

 

It would be an interesting design challenge, though. In my head, the way it would work is quite simple. What would happen is:

• Insert magazine.
• Pull charging handle back. This retracts the air cylinder by pulling it all the way back (cocking it), and chambers one BB and one blank cartridge.
• Pull the trigger. This releases the cylinder and trips the hammer for the blank.
• The BB is forced down the barrel, and the blank fires.
• The blowback system begins to work. I'm seeing a straight blowback system like a 9mm AR-15. The bolt recoils backwards, ejecting the blank, and continues through inertia alone. It needs to recock the cylinder somehow on this recoil stroke, but delayed so that it doesn't suck the BB back down the barrel. A simple operating rod system in the fore-end à la HK 416 would allow a delayed pick-up which would do the trick. Then the bolt strikes some block in the stock tube to generate the felt recoil.
• On the return stroke, the bolt loads another blank and another BB, and is either stopped by a sear (semi-automatic) or fires again (fully automatic).

It is a VERY interesting concept. It could be greatly simplified by removing the spring system altogether and allowing the blank to first push a sprung piston to push the BB, but that's an even closer connection between the gas of the blank and the BB's motion. I will do this thread a favour and send an e-mail to my local Firearms Enquiry Team and ask whether I could come in and ask some questions of them.

[BaBaBooey]

Yes - there's no recoil. My M700 is more or less a spring air rifle and the performance is also about the same. You also have to keep in mind, the system is almost 30 years old. I thought it was unique because at the time it was one of the few bolt action rifles that ejected a metal case after each shot and, as far as I know, the only design that combined the noise/smoke/spark from a PFC and spring air rifle.

 

On the M16, the only thing the blow back action can do is push the air piston back (i.e. cycle the spring system)...the same action also moved the bolt carrier back so the next shell can be chambered. There's not enough energy left to push the BB. When you pulled the trigger, it would both release the piston (which pushes the BB) and push the shell/cap into the detonator causing it to fire. The BB action had to be in the charging handle and the mock gas tube, since you needed a cap detonator inside the barrel. In my opinion, PFC model guns are more or less recoil-less.

[blobface]

This is brilliant, I'm really excited for this project and would pay good money for one provided no upgrades on the airsoft side will be needed! (can't imagine it being less than £1500 if it goes into initial small batch production? )  do you work in fields that involves cad/cam? 

[PureSilver]

Yes - there's no recoil. [...] On the M16, the only thing the blow back action can do is push the air piston back (i.e. cycle the spring system)...the same action also moved the bolt carrier back so the next shell can be chambered. There's not enough energy left to push the BB. When you pulled the trigger, it would both release the piston (which pushes the BB) and push the shell/cap into the detonator causing it to fire.

 

Very, very interesting. A more in-depth examination of this system - and potential developments of it - will depend upon what advice I get from the Firearms Enquiry Team (who I expect will tell me to sod off and talk to either some solicitors or the Crown Prosecution Service). I like the idea of using the blank cartridge's energy to power the BB (probably a closed system which would use the gas first to fire the piston, then to retract it with the bolt, ejecting the expended cartridge and chambering a new one) because it's so simple. The blanks (which have, obviously, much more stored energy than PFCs) are definitely up to the job, and such a system consumes much less space than two separate BB/recoil systems (particularly in something like an AR-15, where moving the recoil system away from the barrel's bore also moves it off the recoil buffer's axis). Plus, using the gas to operate a piston of fixed volume fixes the energy output of the gun, which is useful for consistency and legality. So it's desirable in several ways.

 

The problem is the legality of using the blank's energy to fire the BB, however indirectly. In my head, it's not a problem, because a 'firearm' in UK law is:

 

57 Interpretation.

 

1 )  In this Act, the expression “firearm” means a lethal barrelled weapon of any description from which any shot, bullet or other missile can be discharged and includes—

 

(a) any prohibited weapon, whether it is such a lethal weapon as aforesaid or not; and

(b ) any component part of such a lethal or prohibited weapon; and

© any accessory to any such weapon designed or adapted to diminish the noise or flash caused by firing the weapon;

 

and so much of section 1 of this Act as excludes any description of firearm from the category of firearms to which that section applies shall be construed as also excluding component parts of, and accessories to, firearms of that description.

 

As you can see, the definition of a firearm does not depend upon what projectile the weapon fires, or how the aforementioned projectile is propelled (which is why air weapons are firearms), but on whether it is "lethal" or a "prohibited weapon". Therefore, in theory at least using blanks to fire BBs is not problematic as long as the gun isn't either of those two things. The definition of "lethal" is far from clear in English law, as the CPS unhelpfully explain:

 

Lethality is a complex issue and although case law exists (Moore v Gooderham [1960] 3 All E.R. 575), only a court can decide whether any particular weapon is capable of causing "more than trifling and trivial" injury and is therefore is a "firearm" for the purposes of the Acts. The Forensic Science Provider (FSP) will be able to advise in any case where "lethality" is likely to be an issue. See also: R v Thorpe 85 Cr. App. R. 107 C.A.

 

Airsoft guns in the UK adhere to a 1J energy limit, which is reckoned by the industry to be below the minimum level of lethality, meaning airsoft guns are not defined as firearms for the sake of UK law, unlike air weapons, which are. This distinction is critical, because if airsoft guns were defined as firearms, many of their features (semi- or fully-automatic fire, short barrel or overall length, etc) would fall foul of the "prohibited weapons" provisions contained in section 5 of the 1968 Act (irrelevant sections omitted):

 

5 Weapons subject to general prohibition.

 

(1) A person commits an offence if [...] he has in his possession, or purchases or acquires, or manufactures, sells or transfers—

 

(a) any firearm which is so designed or adapted that two or more missiles can be successively discharged without repeated pressure on the trigger;

(ab) any self-loading or pump-action rifled gun other than one which is chambered for .22 rim-fire cartridges;

(aba) any firearm which either has a barrel less than 30 centimetres in length or is less than 60 centimetres in length overall, other than an air weapon, a muzzle-loading gun or a firearm designed as signalling apparatus;

(ac) any self-loading or pump-action smooth-bore gun which is not an air weapon or chambered for .22 rim-fire cartridges and either has a barrel less than 24 inches in length or is less than 40 inches in length overall;

(ad) any smooth-bore revolver gun other than one which is chambered for 9mm. rim-fire cartridges or muzzle-loading gun;

(ae) any rocket launcher, or any mortar, for projecting a stabilised missile, other than a launcher or mortar designed for line-throwing or pyrotechnic purposes or as signalling apparatus;

(af) any air rifle, air gun or air pistol which uses, or is designed or adapted for use with, a self-contained gas cartridge system;

 

(2) The weapons and ammunition specified in subsections (1) and (1A) of this section (including, in the case of ammunition, any missiles falling within subsection (1A)(g) of this section) are referred to in this Act as “prohibited weapons” and “prohibited ammunition” respectively.

 

(8) For the purposes of subsection (1)(aba) and (ac) above, any detachable, folding, retractable or other movable butt-stock shall be disregarded in measuring the length of any firearm.

 

Just to give you a taste of how complex this is, I tried to draw up a flow-chart of the relevant sections for "prohibited weapons" alone. Follow green for 'yes' and red for 'no', and click through for higher-resolution:

 

 

Try that for size. I'll let you know when I've had a chance to talk to the Firearms Enquiry Team.

 

This is brilliant, I'm really excited for this project and would pay good money for one provided no upgrades on the airsoft side will be needed! (can't imagine it being less than £1500 if it goes into initial small batch production? )  do you work in fields that involves cad/cam?

 

As the above essay might demonstrate, I'm actually training as a lawyer, though I have some engineering experience (in aerospace). The price will of course depend on which system is pursued first - bolt-action will be substantially cheaper than semi-automatic. If anyone wants to commit financially to this over the summer, I'd be very happy to work on a pair of rifles (one for you, one for me) with a working cost of £1250 for a bolt-action.