Female complications, day 29 Air rifle designs.

It's cute when Iselin spends a couple of hours just walking around measuring everything interesting with a caliper. Hair strands; the width and length of knife blades; the size of table top miniatures; the squareness and alignment of the dice; the height and width of her stiletto heels so she can compare between them, and calculate the ground pressure; and how accurate the different telescopic batons really are. And so on. She has very quickly understood the vernier scale and use, and gotten comfortable with it while we have been building, and she is practising making sketches and drawings on paper of what she measures. Iselin likes to make a proper drawing and is adamant that what we build should be properly documented, and has made good drawings on a lot, which will now be better with more accurate measuring equipment. Because of the metronome project, Jane has been working a bit in the workshop, and she has made some snide comments about how nerdy and technically interested Iselin is.

Which Iselin took as compliments.

The construction projects on the island is quite slow due to few daylight hours, snow and cold, but they are really good at what they do and motivated, and now that it has started to thaw they can do more. Kari's construction team helps a lot and are learning. I still feel a bit awkward visiting the construction sites, like the impatient boss pushing is workers in bad weather and working conditions, but I get that they don't see it like that, and I'm way better boss to work for than most Elves with power.

Olafr now work along side Birger, Gaermarr, and the construction teams blacksmith, and they get along well, though it is with clear reverence they address Olafr. Birger and Gaermarr are as pleased as others have been to now be employed by me, and they hadn't expected to be working with someone as famous as Olafr. But they are all learning a lot, even Olafr.

Olafr and I are making progress on the vertical lathe and parts for the milling machine. There are of course problems, and parts we have to redo, but that is important lessons too, and we're all learning from experience and failure. The forge-metal workshop now have a good caliper and a dial indicator, stored in a dedicated small wooden box like the precious things they are. In the future there will be more so every craftsman have their own set of most important measuring tools, and there will be a hard stone measuring table with a box of gauge blocks or at least precision reference blocks.

They have finished the secret security door for Iselin and the issue now is how to install it without anyone knowing. It should be enough that I can get the door into my workshop room. It will be a lot of work to clad it and get it in place.

Right now I'm more interested in a close look at the parts made for my next air rifle prototypes, because there will be two rifles made as I want to test how consistent and similar they will be in performance, and I will want more than one. It's just easier to make several parts at once, and I've saved the prototype for the future. One of these real air rifle prototypes will also be saved for a future museum, but weapons related stuff will be kept secret and not for public viewing until the knowledge has been disseminated-revealed, which hopefully will not happen until long after my death. However, I intend to keep the prototypes in a display cabinets in my office, where few will see them. I should also make a proper safe for storing secrets and sensitive documents. With an alarm. I hope the air siren horn with diaphragm will work, and that it will be loud. I hope the same for the enlarged whistle that is fed by high pressure air. As well as being useful for an alarm, it can be fun, and annoying to others, and a really big loud air horn, whether diaphragm or bass whistle, can be very useful as a ship's horn or a fog horn.

The new air rifle prototypes are designed to primarily utilise the advantage an air rifle have over black powder weapons, which is the all-weather reliability aspect as well as the repeater function with multiple rapid and low signature shots, so these weapons will have detachable single stacked magazines in the pistol grip, and they will be front grip pump-action rifles. The reason for single stacked magazines is so that the pistol grip will fit a smaller hand than mine, such as a shorter woman like Alith. The new prototypes use existing tanks although there are a couple of new smaller and lighter 750cc tanks, but the rest is new and basically I've turned the system upside down to be able to have the magazine in the pistol grip on the underside, so the internal pressure chamber is above the barrel. There are several nice bonuses, like the barrel is closer to the buttstocks point of contact with the shoulder, so should have less recoil rise, as the recoil can be larger than I was expecting, which also means the sights will be high enough above the barrel that a normal suppressor won't block the sight. Also, the feed mechanism and fire selector etc don't have to fight for space with the pressure chamber and hammer, and with a magazine in the grip, the barrel is about as long as it can be without being a bullpup weapon, i.e. with the magazine and mechanism in the stock and behind the pistol grip. The whole air rifle have been designed to look modern and much like a flimsy pump-action shotgun with pistol grip and buttstock, although the body is partially wood, and the buttstock is a cylinder.

The pressure tank is angled slightly downwards at the shoulder for slightly improved shooting position, and the top of the buttstock is shaped wood on top of the metal rail which partially protects and masks the tank, but mostly provides better good nice cheek support. The sides and bottom of the buttstock are a leather pouch that hangs down and around the tank to hide it, where the butt and the rear 'lid' is the shoulder plate that is attached with a hinge to the metal rail, to give a better shoulder connection than the rounded top of the tank. Not optimal, but also makes the length of the tank or exact angle of rotation when screwed on irrelevant, because that is not prioritised in manufacturing and between guns, and the exact length of the tank does not affect shooting position. The entire rear stock can be easily detached for more compact storage or if someone just doesn't like the shape or wants a different model or cheek rest. At the bottom of the stock's leather tank pouch is a magazine pouch for carrying an extra magazine on the weapon, or just a magazine with a different bullet weight. Rear rifle strap lugs are on both sides of where the tank screws into the metal block, which inside the concealing wood is the strongest and most durable part of the rifle, and allows the rifle to hang higher on the body or back if desired, because the barrel is generally carried downwards. Front rifle strap lugs are on both sides just in front of the pump handle, where the front sight is on top.

The backward movement of the pump grip moves the breechblock back and begins to cock the hammer, and when the pump handle is moved forwards, a new bullet is loaded and the breechblock is closed, and once it is closed, the rifle can be fired. If the feed selector is set to manual loading, a dust cover springs open and rounds in the magazine are pushed down enough that rounds are no longer taken from the magazine, and a round needs to be hand loaded from the side, but may also be slightly longer than will fit in the magazine. The open breech and barrel also makes it easier to clean the barrel or push out a stuck bullet.

The ambidextrous power-force selector sits diagonally above-in front of the dust cover and is relatively easy to manipulate whether the shooter is right- or left-handed, and will have three positions; low Force 1, medium Force 2 and high Force 3. It is simply a variable restriction in the air path, which in Force 3 gives full flow, but when rotated introduce progressively smaller holes and greater flow restriction for Force 2 and Force 1. I don't know what energy Force 1, 2 and 3 will correspond to, but these prototypes will be used to experiment with. Simply maximise the energy with the standard heavy slug/bullet and reasonable amount of shots, and then do restrictor holes for desired lower energy levels.

I currently don't know what the final bullet weight will be as the shape and pointedness-hollowness of the bullet affects, which is partly the reason for detachable magazines as I need to adapt the magazine for the bullets being fired. Currently, the plan is a short hollow-point hollow-base slug of about 15 grams, and a longer slug that will probably also be hollow-point or have a hardened steel core. The bullets low velocity and thus high drop, as well as high weight, means that common low-drag pointy boat-tail bullet with a good ballistic profile is probably unnecessary, but experiments will be done. I hope to balance bullet weights and force levels, so that the medium Force 2 mode with the light slug gives the same muzzle velocity as the high Force 3 mode with the heavy slug, because then the slug should have similar long distance drop, and thus make long distance shots easier.

Further experimentation with the prototype has also taught me that the gun will be able to shoot through the sound barrier with a comparatively very light wooden bullet, but it wastes air. Good to have as an alternative though, and a more advanced small hand-cranked copying lathe can reasonably quickly shape a good enough wooden bullet. Just clamp a roughly shaped and long piece of wood in the lathe, and start cranking. The small V-blade sits on a finely toothed rod that is geared down a lot, and slowly works its way from one end to the other. A profile template, which has the profile of two wooden bullets with the tip facing each other, is slowly followed to the other end, where the user have to change the direction of the V-blade so it works its way back. Manually changing direction is easy and allows the operator to more efficiently choose to work where needed, and two bullets are made at once with minimal finishing work. Is it an unnecessarily complicated little mechanism? No. A better bullet is a better bullet even in wood, and without a good profile and balance the wooden bullet starts to tumble sooner, thus limiting range, and changing the profile makes it easy to experiment with different lengths and shapes to find a good wooden bullet.

I've designed for a semi-automatic system, where a rod in a long tube becomes a small high-pressure air cylinder and the hammer activates a small valve to cycle the gun after firing, but that of course requires some extra mechanism and valves. Automatic reloading might consumes high pressure air that can be used to fire a slug, but it should be possible to divert some of the still high pressure air that propel the bullet. I also want to be able to deactivate semi-automatic and reload via pump action, so one prototype gets optional semi-auto, just to see how much it actually affects, and quick semi-automatic fire is something flintlock guns, bows and arrows or crossbows don't have. However, just as a normal Midgård firearm have to be cycled by hand the first time, the air rifle must be pumped.

The rear sight is another thing that will need to be experimented with, as falling pressure and different muzzle velocities with different bullet weights and Force settings makes it much more complicated than ordinary firearms, but subsonic bullet velocity and thus high bullet drop at longer ranges, means that the air rifle will be a limited range firearm for distances less than 200 meters, and not for elk hunting. Due to the expected high bullet fall, there will also be issues with several common rear sight designs. Relatively low bullet velocity of probably around 200 m/s with the heavy bullet, and 9.8 m/s² gravity, means that the bullet drop after sight zeroing at 50 meters, will be around 0.6 meters at 100 meters, and 4 meters drop at 200 meters, and 10-15 meters at 300 meters. Which over the weapon's sight radius of 450 mm, means 10-25 mm difference in height of the rear sight. So, inspired by historical weapons, the rear sight is a folding ladder aperture sight, the sides of which will be engraved for whatever distances are required, and then fitted with suitable locking lugs and perhaps a fine-tuning screw, and when folded down another aperture is the 50 meter 'ghost ring' fast sight. The sight's axis hole is threaded and a simple fine threaded screw can then provide lateral adjustment of the sight, with a faceted screw head and a leaf spring providing 'clicky' lateral adjustment unaffected by shaking and recoil. I would have preferred something like a rotating drum with aperture holes like on the Heckler & Koch MP5a or G3a, which could have worked with high elevation variation, as could a M16 style rear sight or a 3 position rocker, but that is harder to manufacture and get accurate enough and with sufficient elevation variation. I also don't like the notched open rear sight that rise and fall by a bar moving forward or back. The rear and front sights will be detachable though, so it's possible to experiment and hopefully it can be replaced with precision made rocker or drum with drilled aperture holes or similar in the future, as the drum can have 4 to 8 distance graduations, which is more than enough. More work to do, but feels worth it.

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The front sight is a threaded screw with a pointy tip, that screws up or down to zero the sight vertically at 50 meters, and a simple leaf spring and facet ring on the screw lock rotation. The front sight and sight guard are also designed for rough range estimation, using the average height of a man, or the width across the shoulders, which is closer to 1/3.3 of the height. Hardly accurate, but better than nothing, and at the generally shorter ranges below 200 meters which is where the weapon will be used, probably good enough for first shot hits on a standing person aimed at the chest.

There will also be a mount for a telescopic sight, because telescopic sights can be beneficial in long range combat, especially if it helps the shooter make better range estimations, or just see where the bullet hit and can make a correction. A telescopic sight is also a telescope to see better at a distance, and if it is quickly detachable but still holds the zero, it is more practical. Making the guns without a optical sight base or detachable sights would just be silly if I then want it or make a modification, and it is not that much extra work to at least make screw holes and edges to take recoil or impact shocks from side force on the sight and screws and make sure the base doesn't move, so we can attach-screw a scope mount to it.

These prototypes will be suppressed, since that is a really good idea for many reason, but they will be slightly different, with one barrel being a few centimeters longer and with that section ported. My thinking is that since most of the bang comes from high pressure air behind the bullet escaping, venting that air out through the ports in a first stage suppressor around the barrel and going back a bit, means the front part of the suppressor will deal with lower peak pressure and instant air volume, but over a longer time, and thus less noise. The bullet still in the barrel basically works as a very short duration seal. Will it do much of a difference in sound compared to a similar volume normal suppressor? No idea, but worth to try.

I'm actually a bit proud of the three new and improved hand pumps, because they are my very own creations, mostly made on the lathe and vertical drill. Durability and maintenance are incredibly important, because it is very high pressure and with leather gaskets as seals, which will need to be lubricated, adjusted and replaced, and if the hand pump is to be transported, size, weight and practicality are important. The hand pumps have different diameters, in order to be able to experiment with what is suitable for achieving higher final pressure. A large diameter pump can be used to reach a good pressure more quickly until it becomes too heavy to push to the bottom, and then switched to the narrower pump to reach even higher pressure, but a general pump is of course more practical and less total weight. Practically speaking, it will be about half an hour of hard pumping per tank to top them up after use, and differences in tanks and manual pumping will give a lot of pressure variation. It is very impractical and quite hard work to hand pump, but it is possible.

To make the hand pumps 'small and practical', and as there is no armoured high pressure hose available in Alfheimr, one end of the pump screws directly onto the pressure tank, and there is no pressure gauge or similar, although a future version will hopefully have one on the high pressure pump. I hope to give future pressure tanks a simple pressure gauge, just to know their pressure status and when to stop pumping, but that is a lot of gauges to make, so it might just be a pressure gauge on the pump and air rifle, where the air rifle gauge can be recessed into the underside of the rifle and hidden. The pump handle is removable and basically a bent flat iron bar that snaps onto the end of the pump, one end of which also doubles as a large blade screwdriver, and has a couple of square holes for it to act as a ring spanner. Square is just more durable and easier to make than hexagonal. The pump handle is not very comfortable to hold, but it can be used as a foot pump where the handle is down, and the tank is held and pumped up and down. The rounded end of the tank is quite convenient to push down, but there is a simple loop on the pump where a suitable wooden branch can be pushed in to provide a handle. It will probably be a couple of leather tubes that are placed over the tool handle when pumping. A pressure gauge on the pump would be nice and practically necessary, but in the worst case, the user will simply have to count the number of pumping strokes.

Different pumps, lack of pressure gauges, some difference in tank volumes, and that people will pump differently hard, in different temperatures, or lose count, is not good for my hope of consistent bullet trajectory, which is one reason why I given the air rifles an internal pressure regulated chamber. I.e. the tank has very high air pressure, but a simple pressure control valve sits between the tank and internal pressure chamber, which is not particularly difficult or expensive to manufacture. It will be interesting to see how internal pressure regulation perform, because it should give much more consistent bullet trajectory at longer ranges, and we will see how pressure drops over how many shots.

The hydro powered pump has proved capable of filling to more than 350 bar, and the pressure tanks have proved capable of withstanding much higher pressures than we have used so far, which is really scary high pressure, but it is unnecessary and increasing problems with pumping, and partly jamming leaking valves, and it is reassuring to have a good safety margin, so we will fill to 250 bar until we have gained more experience, which is hard enough with a hand pump. But if we need to fill tanks by hand, then it's an emergency and we'll accept such work. However, going up in pressure means more bullets can be fired with the same pressurised tank, so therefore we have made a small increase to 250 bars. It will be interesting to see what these prototype pump action air rifles can do in bullet energy and amount of shots before the pressure drops too much.

Primary filling will be via one of the compressors, and probably the hydro powered one which has also been finalised since Engdrid finished the parts for the water wheel and connection. That compressor hardly looks like a modern compressor, because it is basically a geared stationary bicycle pump that is pumped up and down via an arm from a large wheel. I don't know how much heat there will be from friction and just compression of air, but I guess it will be a lot and considerably more than hand pumping due to the higher pumping speed, so the long cylinder has cooling fins while the pressure tank itself is suspended in a bucket of water during pumping. This also helps absorb any explosion and should redirect more of the blast upwards, and I am worried about explosive failure. However, like all the air compressors it has a pressure gauge and safety valve, where triggering the safety valve stops pumping. Apart from pure safety, the loud whistle gives a clear signal that the tank is filled and time to change for another, reset and start filling that. Holding the tank down in the water and checking for bubbles also indicates a possible leaking valve. The relatively small compressor will be installed in the lower hydropower building and won't take up much space, and if there is a lot of air rifle shooting, one or two more compressors will be made, because about half an hour per air tank means six hours if a dozen tanks are to be filled.

The smaller and tiny electric compressor is slower, but can be operated from the battery bank in Thrymheim, Borgheim, the ship Eagle or where there is sufficient wind power to generate electricity. Its electrical shutdown was much easier to do than the mechanical for the waterwheel, via just electrical contact on pressure gauge that switch off the motor relay. Of course there is extra switching on the pressure relief valve, and everything physically cut power to the motor which must be manually reset. The electric compressor also got a permanent small pressure tank, which is two 1000 cm³ tanks, just to save time when filling. A rifle tank or several can be pre-filled from the two combined tanks, before valves are switched and the air compressor tops up the air rifle tank or tanks. This speeds up filling. The air rifle tank is generally not unpressurised and empty, but only to a low enough pressure that the muzzle velocities is 'too low'. Depending on when that 'too low' line is drawn, there can be 50 to 150 bar of pressure still in the air rifle tank.

I still want to improve filling tempo, and consider making a larger tank that can be pre-filled to the water wheel compressor, or just interconnected many tanks to a large combined tank. Of course, the pressure will drop in the large tank or combined tank as smaller tanks are filled, and the small tanks will not be fully pressurised. But if, for example, eight smaller tanks can be filled to 70% before each is put on the air compressor, then a lot of time is saved. I can install a small wind turbine at the range that drives a high pressure air compressor and slowly fills a larger combination tank, making high pressure air available for refilling. A similar deadweight valve system that shut off the hydro driven compressor, can shut off pumping and block the wind turbine. In fact, it is a solution that can be used in many places, just to have high pressure air available, and requires relatively little in metal, work hours etc. If a wind turbine compressor with a large combination tank system is made and geared to filled to 300 bar, then there just needs to be a simple regulator to allow filling several air rifle tanks to full pressure 250 bar. And it will also be a long term test of tanks under such high pressure, and the whole tank installation can be made safe, so if-when a tank in the combination system bursts-leaks etc, no one should get hurt.

Ugh. Just how many weapons projects have there been since I ended up in this world?

The problem is that I'm way too good at getting ideas and seeing improvement opportunities. I've even tried making a mechanically very simple muzzle-loading single-shot airgun. A barrel is surrounded by a larger cylinder which is its permanent air tank, and the barrel ends a few centimeters in from the rear edge of the cylinder where there is a Schrader-like filling valve. In the space between the back of the barrel and the valve is a small metal block with barrel size hole and leather seals against and around the barrel. When the air pressure starts to build up from filling, the air pressure force the block against the barrel and seals it. The block isn't completely sealed against the side of the cylinder, so pressurised air flow past and starts to fill the front of the cylinder around the barrel. Eventually the desired pressure is reached, and the air pump is removed. The air pressure is the same behind and in front of the block, but the surface area is larger at the rear, so the barrel is kept sealed. A bullet can carefully be muzzle-loaded. When firing, the Schrader valve is quickly pushed in, preferably with a simple spring-loaded mechanism that quickly opens the valve, and the compressed air in the back flows out. This creates a pressure difference between the front and back of the block, and the air pressure at the front force the block back. The block no longer seals against the barrel, so the compressed air rush into the barrel forcing the bullet out. Bang!

This makes for a functional single-shot airgun that looks like a thick rod, but its usage is very limited, and it doesn't feel safe to load a bullet into or to carry. I also don't know how long term air sealing will be, or if it slowly leak air without it being noticeable. It should have a pressure gauge, which is doable. A suppressor with the same outer tube diameter as the cylinder can be attached at the muzzle, and just make it a longer rod. It is easy to make it look like some kind of cane, baton or magicians staff with a trigger, but a cane will be quite thick and heavy but could be made to look like a regular one. Just a small diameter barrel and long cylinder tank for an overall thinner rod-cane-staff while still having enough air volume, and shoot something arrow-like. It should be a practical design for something that can kill-severely wound with its one shot. But it's not really a good practical weapon to carry, and except for self-defence, the weapon really only has one purpose, and that is assassination, although the sound might be difficult to conceal.

Because of this, I have not told anyone about this airgun design.

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