ho trovato qualcosa :
http://www.thehuntinglife.com/forums/to ... djustment/
http://www.network54.com/Forum/79537/th ... 00+trigger
e qui un sunto di un altro articolo di Ian Pellant ( ho evidenziato in rosso la parte che parla del grilletto, appena posso la traduco, questa sera sono troppo stanco, abbiate pazienza:
CZ 200 - A Czech of Many NamesBy Ian Pellant
A New Air Rifle
Over the past few years I have developed a peculiar fascination with entry level, target grade CO2 guns. It started with a Tau 200 rifle, then an Aeron Chameleon pistol followed by the Chameleon rifle. The modularity of the Aeron guns displays great ingenuity. Take a trigger, valve and auto-cock striker unit and furnish it with single shot or magazine loading and Aeron had the basis for two pistols and two rifles. Tau produces an array of pistols based upon their one basic action, and several versions of the 200 rifle with different stocks and sights. Czech airgun philosophy seems to be to take a good, well designed and proven base unit and extrapolate that into as many variants as possible.
I kept wondering what new and innovative airguns may arise from those fertile Czech designers.
So it was when my February 2001 copy of the British Airgun World magazine arrived and opened on the centre pages, I saw photographs of a new pre-charged pneumatic (PCP) rifle that just had to be Czech... Yet the title read Air Arms S 200. Very interesting.
Reading the article proved more tantalizing. It mentioned that the rifle was a collaboration between Czech CZ Brno and British Air Arms. The CZ Brno reference confused me a little. Aeron and Tau manufacture airguns in Brno. CZ manufacture airguns in Uhersky Brod. There is quite a distance between Brno and Uhersky Brod both in kilometres and airgun manufacture as we knew it. The contemporary CO2 guns are made in Brno, the older style Slavia spring airguns are made by CZ in Uhersky Brod. Scrutinizing the magazine photographs revealed lettering that read "CZ 200 Made in Czech Republic". Interesting had become intriguing. Just where was this state of the art air rifle made?
As the months of 2001 ticked by, there came reports that the rifle was being withheld from production due to negotiations with Daisy in the US and some design changes were being made. This was most teasing. When would this rifle be released and how would it be imported to the United States?
Then in the August issue of Airgun World, an article appeared featuring the production version, the gates were opened and the race to the stores was on. More orders were being taken than there were units to ship. Months passed.
The Daisy web site revealed that they were releasing a new Avanti target rifle that could only have been a variant of the 200. The Air Arms web site showed their new S 200 and the Avanti, but did not implicitly link the Avanti to Daisy. So the Air Arms S 200 is a CZ 200 and the Daisy Avanti is a CZ 200, but the Air Arms and Daisy guns are not the same rifle.
The Avanti is a 10m Target rifle set to less than 6 foot pounds (fp.) muzzle energy whilst the Air Arms S 200 is set to the UK "full power" of 12fp. / 16 Joules. If I wished to buy the rifle in the US, I wanted the Air Arms UK specification, not the Daisy Avanti model. I have two excellent Czech 10m target CO2 rifles and have no need for another 10m rifle. Also, I wanted a .22 calibre model for the greater air efficiency and lower noise in a pre-charged pneumatic.
So, the search for the Air Arms S 200 in the US began. "European Air Pistols" was the name of the importer for Tau, Aeron and Air Arms. Perhaps they would know. But: their old web site was gone; the old phone number was disconnected. In exasperation I emailed Air Arms and Bill Sanders replied: "give me a call". Bill told me that a shipment was on its way to the US and that European Air Pistols was now trading as "Topgun". Do not ever attempt a web search on "topgun" unless you wish to prove the ineffectiveness of web search engines!
I emailed Boris Plesinger and discovered that their new name is Top Gun Air Guns Inc. However, the shipment of S 200s was not expected for few months. Wait a little longer.
In early May, the shipment of CZ 200s in Air Arms S 200 livery arrived in the US. I quickly placed my order. A week later I unpacked and admired my new rifle. It was worth the wait.
The first impression on seeing the box was that the rifle must have been packed in pieces. No: it really is a compact rifle.
Before reading the instructions or attempting to put air in the rifle, I decided to see how it looked with a scope attached. The nearest scope to hand was a BSA 6-24x 40mm with some Tasco "sight through" rings. By chance it came together reasonably well
With a long scope, the S 200 looks a mean machine.
The deeply cut pistol grip is distinctive and so is the two piece stock with the exposed breech block between. The block and trigger guard silhouette is a signature of the CZ 200 series. Follow the angled cut back edge of the fore-stock downwards in an arc over the trigger, then swing it back up to the front edge of the butt stock and you gain an appreciation of the aesthetic.
For someone more accustomed to spring piston air rifles, the compactness of this rifle is hard to describe. At just on 907mm (35.7") short and weighing in bare at less than 2.65 kg (5.8 lb.), it is a very poignant package.
Why the CZ 200?
Ignoring the "boys toys" impulse to collect new gadgets, my interest in the 200 had stemmed from a need to fill a niche in my air rifle inventory and experience. I did not own a UK "full power" / 12fp target quality / recoil-less air rifle. The only real choices in the category are pre-charged pneumatics (PCP) or some quite exotic (and heavy) double piston or sliding action spring rifles. I also had a collection of orphaned telescopic sights that needed something to sit on. I did not have a pre-charged pneumatic…
Benjamin / Sheridan rifles don't count.
Despite the virtues of PCP I have been resisting the push to pre-charged air because in the US there are a few peculiarities:
* Most imported air rifles are "export models" (British FAC), set to over 12fp muzzle energy, usually up to the maximum power rating which can be over 18fp up to 50fp or more, which can be very noisy.
* Most British airgunners would not consider using a PCP without a sound moderator because of their customary high noise. There is an abundance of sound moderators for sale in the UK, but In the US, airgun sound moderators are legally confused with firearm silencers and are restricted from sale.
* SCUBA (Self Contained Underwater Breathing Apparatus) tanks can require legal exceptions to be written and agreed before a dive shop will sell and refill a tank in the US. This is a public safety concern to prevent uncertified people attempting to SCUBA dive and drowning themselves. So just filling a PCP with air is a hassle unto itself.
The combination of unnecessary high power and noise, unavailable sound moderators and the fuss of buying and filling SCUBA tanks, have been deterrents to me bothering with pre-charged pneumatics. In recent years specialised manual pumps have become available that circumvent the need for SCUBA. Almost a return to the early days of airguns, except modern PCP's operate at several times the pressure of those early guns.
However the rifle choice in the US was still restricted to what I nick named "pneumo-blasters" ("pneumo" from "pneumatic"; "blaster" from "ghetto-blaster" / noisy). That was until the Air Arms S 200.
What is the CZ 200?
Air Arms advertised the S 200 as: "Pre-charged sporter. Small in size BIG on performance. Designed to fit below the sensational S 400 range bringing the benefits of pre-charged shooting to the masses." That sums it up quite nicely.
More prosaically, the instruction booklet states:
"Series CZ 200 PCP (pre-charged pneumatic) air rifles is a result of the close co-operation between Czech arms factory Ceska Zbrojovka and renown English air guns manufacturer Air Arms"
"Model CZ 200S PCP air rifle can be designated also as Model Air Arms S 200."
"Model CZ 200T PCP air rifle can be designated also as Model AVANTI Valiant."
Each of these models sport different woodwork and power levels. Models CZ 200 and CZ 200S have the muzzle energy set to either 10 Joule (7.38fp) for the Czech or 16 Joule (11.8fp) for the UK markets and are available in .177 and .22 calibres. The CZ 200T is set to a 7 Joule maximum for indoor target shooting in .177 calibre only.
This versatility comes with the modularity of the design which consists of:
o Breech-block and trigger unit. The bolt and striker are in this unit which is tuned for specific power outputs with a matching calibre barrel.
o Compressed air reservoir. There are two versions of this. The target model has a pressure gauge on the end so must be removed for filling. The sport model has a quick connect adapter instead of the pressure gauge so it may be filled on the rifle. The firing valve is part of the air reservoir so there are no high pressure valves in the breech block.
o Barrel assembly. The barrel is easily removed from the breech block by loosening two screws. It may be possible to exchange barrels of one calibre for the other; however the power level would probably require re-adjustment. The simple muzzle fitting may be replaced with a sound moderator or dovetailed unit for a target front sight.
o Two-piece stock. The forestock comes with an accessory rail for the target model. The butt stock may have a slant or vertical pistol grip with or without adjustable cheek rest and butt plate.
o Sight system. The rifle often does not come with any sights attached. A 3/8" dovetail system provides the base for almost anything. The Daisy Model XS40 Valiant comes with match target sights which slide onto the dovetails.
Wow. A lot of options. By changing the stock and power configuration with different sighting options, the rifle can fulfill a variety of roles.
With all of these options, the CZ 200 is amongst the most adaptable air rifles on the market. If you ever see an air rifle with a two piece stock and the distinctive breech block and trigger, then you can be sure it is a CZ 200. Only southpaws (left handed users) may be a little compromised:- the stock is ambidextrous, but the bolt action is right handed.
Two screws and a nut are all that hold the main component modules together. The barrel is effectively free-floating. There is negligible support from the front scope block, if used. What does concern me a little is that the forestock relies mostly upon the air reservoir for holding it in place. A small screw and a small side overlap are the only support it receives from the breech block. It feels rock solid, so maybe I'm fussing over nothing, but I will be careful about handling the rifle when the air reservoir has been removed.
My rifle is a little different from those illustrated in the instruction booklet. It was built in December 2001, by which time a modification had been made:- instead of using a long bolt to hold the butt stock to the breech block, a bolt and nut had been substituted. That nut will drive you nuts unless you have, or make a tool, to remove it. More on that later.
The Air Arms S 200 was to be priced very competitively at just over UK £200; it rose to around UK £219 at time of release and may be seen as high as £239 with charging adapter.
The US prices vary between $400 to $500 depending upon whether it is the Air Arms or Daisy model. The Daisy comes with target sights and an adjustable stock which the Air Arms does not.
Before shooting the AA S 200, some sighting arrangements must be made, usually by adding a telescopic sight.
Fitting a Scope.
I almost invariably encounter a glitch or two when fitting a telescopic sight to an air rifle. Often the dovetail grooves are spaced differently to the mounts I have on hand, or the receiver on the rifle has a curved top which doesn't suit flat bottomed mounts, or the mounts are not the right height, or the scope is too long, or something…
The CZ 200 has a flat top 3/8" standard dovetail on the breech block and an auxiliary front mounting block on the barrel. The front block can be relocated into two primary positions to best suit the length of the sight. Surely it should be simple to mount sights on this rifle? Right? Well… almost.
The CZ 200S is designed to be a "scope only" rifle. This is very obvious if you pick up the bare rifle and try to sight directly along the top of the barrel. It is almost impossible to do so on this rifle. The drop of the butt and cheek height of the stock have been set to suit the largest scope anyone is likely to fit. Large front objective lens scopes need to be mounted high to clear the top of the barrel and if the dovetail on the rifle is close to the top of the barrel, then "high mount" scope rings will be needed. Such is the CZ 200. I found that the scope centre needs to be between 46mm and 50mm above the bore centre to be a comfy fit.
"Fit" of a scope is important for both comfort and consistent accuracy. A simple test is to lift a scoped rifle so the butt is contacting your shoulder, but the muzzle is pointing at the ground in front of you. Then whilst looking at your target, lift the rifle up into the shooting position. If the rifle can be swung up till the stock kisses your cheek and you can see clearly through the scope without moving your head, then you have a good fit. If you have to move your head back or forth to focus the scope, then the scope is not positioned correctly for eye relief. If you have to lift or lower your head, then the scope mounting height is incorrect. I found that medium and low height scope rings placed the scope centre too low on the rifle. Besides being uncomfortable, a low mounted scope reduces the space over the breech; space that is needed for your fingers to load the pellet.
I tried a one piece mount that showed promise. The front mount block on the barrel was moved to its' forward position and the scope mount fitted nicely. The scope centre was at a comfortable height, but there were two failings:
1. The scope was too far forward for correct eye relief and could not be moved any further rearwards.
2. The mount placed directly at the front of the breech opening obstructed finger access so pellet loading was fiddly.
Using two rings in the same position as the one piece mount would have the same failings. The one piece mount cannot be fitted anywhere else along the breech block without covering the opening. That would really complicate loading a pellet.
Two rings are needed. Ideally, the rearmost one would be located on the breech block behind the loading slot while the foremost ring would be located on the front mounting block along the barrel. And, the rings need to be high.
If you have ever bought a red dot sight, there is a chance that it came with a set of 30mm rings that will not fit any air rifle dovetail you have ever seen. These wide bases are (W) Universal mounts which are common on handguns and shotgun mounts. (Red dot sights are often fitted on slug and shotguns in the US for turkey hunting.) A year or two back, I had happened upon some Tasco Adapter Bases that convert 3/8" dovetail to (W) Universal mounts and bought a couple of sets, just in case they may be useful. Tasco rings to fit the Universal mount are very common and inexpensive, so on a pneumatic airgun where recoil is non-existent a scope mounting system based on these adapters and Universal rings became my choice for the S 200.
The Tasco Accu Dot sight was reunited with the rings that came it with and three candidate scopes were fitted with 1" Universal rings. The adapter blocks are fitted on the rifle in positions that allow each of the sights to be located at optimal eye relief.
The facility of this system is very pleasing. The Tasco Universal rings have large finger knob nuts. A coin or wide blade screwdriver could be used to tighten the rings to the base, but is unnecessary. Finger tightening is sufficient. It takes 5 seconds to remove a sight and 10 seconds to fit another. The tightening bolt in the ring base fits into the cross slot in the adapter base so positioning is very quick and secure. At last I have a quick, positive, no tools sight mounting system for an air rifle. A modular sight mount for a modular rifle.
As a point of interest, the synthetic "pellet channel" is held in the breech with two screws. (Seen in the photograph: one on each side of the bolt probe) This implies that it is designed to accept an alternate mechanism such as a magazine feed. I wouldn't be too surprised if there is repeater model of the CZ 200 somewhere in the works.
Metalwork
All of the metalwork on the rifle is of high precision machining with no evidence of hand finishing. The breech block and sight base, are of anodised alloy. The barrel is of polished and blued steel and the air reservoir is of matt finished steel. The surface finishes are first class, but as with all alloy components onto which a scope will be mounted, care must be taken if the surface finish is to be preserved. I have yet to find a convincing re-finish for black anodised alloys. The matt finish on the air reservoir is easily marked, but not easily retouched.
The one thing I find delicate with the entire rifle is just how close the air reservoir is to the underside of the barrel and how long the reservoir is compared to the space between the forestock and the muzzle fitting. My new rifle came with a small scratch under the barrel and another on the underside of the muzzle fitting. These were probably made in the factory when the rifle was assembled and tested. The air reservoir also showed long surface scuffs and rotational scuffs where it had been screwed in at the factory, and then out by me. Yes, I know I'm picky.
Except for the ease with which the ham fisted could mar the surface finishes, the rifle is sufficiently robust to take all normal wear and tear for many years. In terms of modern airguns, PCP's are newcomers of little more than a decade in production. Unlike spring airguns which we expect to last a lifetime, how durable do we expect PCP's to be? With a removable air reservoir, I favour designs like the S 200 to be longer lived than those with fixed air tubes for the simple reason that the least durable part can readily be replaced. It is also reassuring that Daisy also sells the air cylinder as a separate item.
Woodwork
The stock woodwork is very well shaped and finished in a mid-red-brown stain and satin finish. The colour may have changed from the first production stains which were reported as being too pale for the British palate.
The finish to the inside of the fore-stock was spiky. Apparently the wood had not been sanded after the stock had been stained and finished. The result was a lot of little spiky wood fibres becoming glued in an erect position. These spikes very quickly left their mark on the matt finish of the air reservoir. Removing the forestock and running some glass paper inside easily resolved that little annoyance.
My guess is that the stocks are made on state of the art machines, virtually untouched by human hands… for if they were, the sharp edges would be noted. The first sharp edge I encountered was the leading edge of the cheek piece cut out. When pulling back on the bolt, the back of my thumb hit the edge, and it hurt. A light rub with fine glass paper followed by a dab of Lemon Oil softened the edge nicely.
The second sharp edge that needed more drastic treatment was found by my trigger finger between the first and second joint. The more I carried the rifle, the more my finger was being abraded. The problem is a sharp transition from vertical to horizontal on the RHS of the stock between the pistol grip and the trigger guard and a pinch point where this edge blends to the curve on the grip rise. I find that when I carry the rifle, I hold it by the pistol grip in my right hand, which puts most of the weight on my forefinger. The sharp edge on the stock and the pinch point in the corner was chewing my finger.
The edges were carefully sanded and blended to the curve (see photograph). Take care, work slowly and gently and test the results by gripping the stock and moving it about as if you were shooting. Because the stock is ambidextrous, it is easy to compare modifications to the other, untouched, side.
This gentle reshaping removed some of the annoying finger rub, but it still makes its' presence felt after an hour or two of shooting. A more extensive reshaping will require a full stock refinish. A future project, perhaps.
Whenever the wood is shaped beneath the depth of colour stain, restaining is required. I have a variety of tins of colour wood stains. Different brands have different interpretations of colours. My stock is a fair match to "Red Mahogany" with a dash of "Walnut". A smear of two of Stock Oil over the stain and the job is done. Sounds simple, but allow a day or two to retouch the stain and finish.
Trigger
The factory settings for the trigger on my rifle were a good compromise for most buyers. All indications are that my rifle was configured for the UK market. Trigger pull weight was 1.5 pounds force (6.6 Newton) with about 4mm slack take up and another 2mm travel before discharge. Not bad, but from my contemporary Czech CO2 guns, I knew that some tweaking would smarten it up.
The instruction booklet is a bit vague on trigger adjustment. The specifications state trigger pull to be adjustable between 2 and 12N ( 0.45 to 2.7 lb.), so the factory setting was roughly in the middle.
As a tongue in cheek comment: It seems that Czechs prefer light, single stage triggers and Brits prefer light two stage triggers. Americans generally have to suffer heavy child proof devices specified by the legal department. From the Daisy web site, there is a Warning note for the Avanti that reads:
"This gun has no safety mechanism as permitted by ASTM standards. The trigger pull is capable of adjustment below the 3lb. level. When adjusted below 3lb., the gun may fire when dropped."
Do not make a habit of dropping the rifle.
Of course, I just had to fiddle with the trigger. It had taken me a while to fine tune the trigger on my Tau 200 to a zero creep 4oz. (1N) by understanding how the first two screws adjust slack and overtravel and the third screw adjusts pull weight.
On the CZ 200 my first adjustment was to the pull weight by turning the screw behind the trigger guard counter-clockwise. It didn't seem to behave correctly. Something was not quite right, so I pulled the stock off and removed the single screw that retains the trigger guard. The "lever spring" had wound itself onto the adjustment screw. The screw has a tapered point that the spring is meant to sit on. The screw is threaded up to the taper, so as it is turned in it tends to wind the spring onto itself. This confused the spring compression adjustment. I searched through my small washer boxes and found some small brass grommet bushes that fit very nicely into the spring and onto the end of the adjustment screw.
With the lever spring adjusting normally, it was simple to reduce the trigger pull down to just over 2N (about 10oz., actually). To adjust the trigger release point it is necessary to slowly adjust the front two screws in the trigger base. Note that if the trigger blade has been slid forward, the second screw may be hidden. Imagine these two screws acting on the trigger lever as if they were the stops on a see-saw; they control how much the trigger base can move before transferring motion to the trigger lever. It is a balancing act between how much the trigger moves before taking up the slack and then how much further it moves before tripping the lever.
With small, careful adjustments it is possible to set the trigger to be a fine zero slack target style hair trigger. The action should be cocked (obviously unloaded and pointed in a safe direction) when making adjustments. If you adjust too much, the trigger will fire. Adjusting on an uncocked action may result in a setting that prevents the action from cocking. If this sounds intimidating, DON'T try adjust to the trigger… take it to your airgunsmith. Responsibility for safety rests in your hands.
Also note that the rifle does not have any safety catch. If you have cocked and loaded the rifle and need to render it safe without firing it, you can open the bolt, slide it back then hold it and then pull the trigger to release the striker and then let it pull the bolt closed against your hand resistance. If you do not hold the bolt it will fly forwards with the striker, slowing it enough to prevent a full power air release, but possibly with enough to expel the pellet. Never leave the rifle with a pellet loaded in the breech unless you intend to fire it before you put the rifle down. A loaded airgun should never leave your hands. The dumbest thing would be to leave a pellet in the breach, put the rifle down, then later pick it up and cock it and put another pellet in the breech, then shoot and jamb the barrel.
Power Adjustments.
Before proceeding, I must make the minor complaint that sometime between early 2001 and December 2001, CZ substituted a bolt with nut for the original bolt that holds the butt stock to the breech block. This change is not shown in the instruction booklet that came with my rifle, so it blindly describes "disconnecting the screw situated in the pistol grip" as a part of normal disassembly for cleaning.
The new nut and bolt will defy most tool boxes. The nut is round with a slot. A screwdriver will not work, neither will your trusty socket set provide a solution. Suddenly a simple job becomes impossible without a special tool, which you will probably have to make.
I managed to find a piece of steel tubing (9mm OD / 6mm ID) in my scrap box and filed the end to leave two stud projections. With this tool, it is a simple task to remove the butt stock; without it, forget it.
My complaint is that my Air Arms S 200 did not come with any tools; not even the 2mm and 2.5mm hex keys needed for simple adjustments. It would be nice if those hex keys plus a nut remover were provided with the rifle.
Because the CZ 200 is a component design that can sell in different markets, there are two main power ranges that the rifle is configured for:
o 7 Joules / 5.16 foot pounds muzzle energy for the Avanti target model
o Up to 16 Joule / 11.80 foot pounds energy for the sporting models. The Czech domestic model is set to 10 Joule maximum.
Muzzle energy in a pre-charged pneumatic is a result of how much high pressure air is provided behind the pellet to accelerate it down the barrel. The quantity of air depends upon static pressure in the reservoir and how long the exhaust valve to the reservoir is held open to let the air out. But it's not quite that simple because the static pressure is dropping with every shot so without some sort of metering device, the quantity (volume) of propulsion air, which is a function of pressure and duration, will vary too much as static pressure drops.
In advanced PCP airguns, the pressure to release energy problem is usually resolved by fitting a "regulator" that is an intermediate air chamber set to retain constant static pressure regardless of the pressure drop in the main reservoir. Such devices are expensive and require careful setup for the desired power output. The CZ 200 is an "un-regulated" design. To achieve a reasonably flat muzzle energy to static pressure performance curve, it relies upon setting how hard the striker can knock the release valve open and then balancing how quickly that air can reach the breech by constricting it through a venturi.
On the CZ 200, the striker force is controlled by the "weight" of the striker main spring and how much pre-compression it has. The pre-compression is adjusted via a screw at the rear of the breech block. This screw is sealed in position by a red compound as a warning to the owner and an indicator to others that someone has been fiddling with the power settings. In any country with legal power limits on airgun, DO NOT adjust this screw unless you are willing and capable of accepting full responsibility if the result exceeds the legal limit.
To fine tune the air release, a venturi adjusting screw is located forward on the right hand side of the breech block. Unless you have a reliable and calibrated chronograph, do not play with this screw. It is mainly intended for factory adjustment of the muzzle energy to below the legal limit before shipping.
In the US, there are no legal muzzle energy restrictions, but do not use this as a license to play with the factory settings. A chronograph and a lot of testing is needed to ensure that the pressure / energy curve is acceptable. As the static pressure in the air reservoir drops, the striker force must be balanced with the venturi restriction to meter more air at lower pressures to be similar to the lesser discharge period at full pressure.
To add a little spice, I purchased a "FAC" spring as an accessory to my rifle. This spring replaces the normal striker spring and takes the .22 rifle up to 18fp. muzzle energy; it is not suited to .177. My rifle is .22 calibre, which in a PCP usually means more shots at full power setting than the equivalent gun in .177 due to the improved air efficiency derived from the larger volume of the barrel. A .22 barrel has almost 50% more internal volume than a .177 barrel (of the same length). With the increased bore volume of the .22, releasing more air by fitting a heavier striker spring is more successful than fitting the heavier spring in a .177.
Before contemplating making adjustments, it is prudent to profile the factory settings.
Initial testing was with a Combro cb-625 Chronoscope attached to my rifle. The little Combro is convenient, but without keeping an extensive paper record, it is tedious to use for a long series of shots. So out came the Shooting Chrony. The S 200 was pumped to an indicated 175 bar and shooting began using Gamo Hunter pellets which weighed an average of 15.3 grains.
After a surprising 80 shots, the static pressure had dropped far enough that the lower velocity could be heard as quieter muzzle discharge and impact in the pellet trap. Another 10 shots were squeezed out just to confirm how quickly velocity would drop.
Typically with PCP airguns, velocity at full air pressure charge is lower than later in the series when the pressure had bled off a little.
Tabled shot strings indicate that my rifle comes up to optimal after 10 to 20 shots then attains a maximum at around the 40th shot.
Shots Average Velocity (fps) Extreme Velocity Spread (fps) Average Muzzle Energy (fp)
1 - 10 561.53 16.55 10.72
11 - 20 582.22 19.35 11.52
21 - 30 593.40 13.47 11.97
31 - 40 601.16 12.06 12.28
41 - 50 598.83 11.81 12.19
51 - 60 593.03 24.76 11.95
61 - 70 578.65 17.06 11.38
71 - 80 546.48 61.06 10.15
81 - 90 477.73 43.48 7.76
I noted that my Shooting Chrony on average was displaying 5fps more than the Combro was during this test. Allowing for this as a higher than correct reading, the average high muzzle energy would be much closer to the 12 fp. maximum that the rifle was factory tuned for. Even so, the Combro was calculating muzzle energies in slight excess of 12 fp during the test. I had weighed a sampling of 10 pellets from the tin before the test, but not all.
To get a better picture of the results, I loaded the strings into a spreadsheet and charted them:
It can be seen that some shots were spiking above the norm. These pellets may have been lighter weight than normal, or the chronograph was recording erratically. Only a few shots drop beneath the norm. It's no wonder statistical analysis is used to try and make sense of experimental measurements because any single point may not be representative. Quantifying airgun performance can become elusive unless everything is meticulously measured and weighed.
Unless the maximum number of shots is needed for an expedition, the best recommendation seem to be to establish the fill pressure that marks the beginning of the optimal velocity range and then count on 40 or so top power shots.
The Air Arms web site shows:
S200S Specification
O/A length 910mm
Calibre 4.5mm(.177") & 5.5mm(.22")
Barrel Length 485mm Stock Beech
Weight 2.65kg Std power 10.5-11.0 ft/lbs
Loading Bolt action Shots 35 (.177") - 50 (.22")
Filling pressure 190 bar (2750 psi)
The standard power and number of shots figures do seem a little conservative. I filled my rifle to an indicated 190 bar and the first shots were very low at around 8.3fp. This is a limitation of most PCP guns; put too much air in them and they will begin to lock the exhaust valves. The striker will not be able to open the valve fully and power will be low until the static pressure drops into the optimal range.
The disparity between number of shots that I achieved with 175 bar and then the onset of pressure lock when pumped to 190 bar, began to worry me. Either the rifle was not setup correctly or the pressure gauge on the Hill pump was reading low… more on that later.
Within the Air Arms specifications, filled to a true 190 bar the average rifle most probably will produce 10.5fp. After 20 shots or so, the muzzle energy will probably peak at close to 12fp. After 50 shots the muzzle energy will probably have then fallen back to around 11.0 fp.
In practice, the hunter who fills to 190 bar and only makes a dozen shots per outing, will probably never get the maximum velocity out of the rifle… But then he'll probably never shoot the rifle in that grey zone nudging over 12 fp.
Accuracy
The CZ 200 S is amongst the most accurate air rifles available today. It is essentially a junior 10m match target rifle that has been uprated in power for sports shooting. The trigger, barrel, stock shape and lack of safety catch all derive from the target heritage.
My rifle came with a factory test sheet printed from an electronic target system. It indicates 5 shots at 10m with a centre to centre spread of 1.9mm (0.075"). To put that in perspective, it is about half the spread (twice as good) expected from the very best sporting rifle a few years ago; and about twice the spread (half as good) expected from a specialised 10m match rifle costing three to five times as much. Considering that the Air Arms S 200 is amongst the least expensive PCP rifles available in mid 2002, it is a remarkably accurate airgun.
Any missed shots will mostly be the fault of a poor scope, pellet or shooter goof than any shortcoming of the rifle. It is very accurate and in .22 calibre does not seem to be pellet fussy. All RWS and Gamo pellets shoot reliably and maintain the target zeroing. Crosman Premiers are okay, but tend to have a slightly different impact zero. For those that know: I am not a Crosman pellet fan; but that's another story.
Noise
I have not quantified the muzzle noise made by the S 200, but it is a bit noisy.
Subjectively, the CZ 200 set to 12fp. emits a sharp muzzle exhaust note accompanied by more air jet noise than my BSA Supersport of the same calibre set to 14fp. muzzle energy. Pneumatics are inherently noisier at the muzzle than piston airguns due to the greater volume of exhaust air. Piston air rifles usually have fully accelerated the pellet within the first 150mm of travel from the breech. From there on, the air behind, which was heated by the sudden compression from the piston, is cooling and contracting and by the time the pellet reaches the muzzle, the air behind it is moving slower than the pellet. Pneumatics on the other hand will accelerate the pellet as long as there is high pressure air behind it. And the air is cooling from ambient temperature, so it needs more than the piston gun. Balancing air pressure and volume (by the dwell of the firing valve being open) to dumping excess air from the muzzle, is the challenge in pneumatic airgun design. The CZ 200 does a good job.
For indoor target shooting with the CZ 200 S at 16J muzzle energy, the noise is obtrusive compared to piston rifles of similar power. I have no idea how effective a sound moderator is on the rifle, but would recommend one where available. On the other hand, the CZ 200 T (Avanti) at 7J muzzle energy should utter little more than a "phut".
The Hill Pump.
The Hill Pump Model 2128 Air Compressor Pump was the first choice for filling the S 200 with air. It was advertised as being "considerably more advanced than anything else on the market" on the same page as the S 200 in Airgun World, February 2002.
The foot plate carries the Air Arms logo which looks cute, but is not particularly functional. I found that left on a carpeted floor, the pump would slowly lean forwards (over the top of the "A") and then fall over. This is a particular worry since the rifle may be on the floor in front of the pump. Placed on a hard surface, the pump becomes much more stable, but on carpet or outdoors, some sort of board is required to keep the pump upright.
My other gripe with the pump is that the short, thick and stiff hose projects from the front and cannot be kept off the floor. It is difficult to keep the charging end of the hose in a convenient (and clean) storage location. It also requires the rifle or the pump to be moved when connecting the two together. A longer, more flexible "micro bore" hose would have been nicer. And a clip to hold store it against the pump tube would be even nicer.
But once connected, pump efficiency cannot be faulted except that I initially ran out of steam at an indicated 175 bar (2600 psi). Pumping is mainly muscle to lift, then body weight down by flexing the knees, so pump resistance and body weight are the limits in how much pressure you can achieve. The pump is rated to 230 bar (3300 psi.) recommended maximum.
It takes 55 pump strokes to fill the S 200 air reservoir from 50 to an indicated 175bar. That's over 70 full power shots that would take 8 or more pumps apiece with a Benjamin Sheridan type multi-pump pneumatic. Calculate that to be 560 Benjamin Sheridan pump strokes, to almost equal 55 Hill pump strokes into the CZ 200. The Hill pump with CZ 200 wins hands down in efficiency.
One thing that concerned me was the moisture trap on the pump began to emit an oily brown sludge after half a dozen fills of the rifle. This seemed to be factory excess lubricant off the pump rod. However, the instruction sheet that came with the pump bears a label stating that the pump was factory lubricated with Super Lube Synthetic Lubricant with PTFE, distributed by Loctite. I special ordered a tube from the local Loctite agent and when it arrived discovered that Super Lube is a clear gel, made by Synco Chemical Corp (Loctite is not mentioned on the label). I wiped the brown gunk off the pump rod and smeared some new Super Lube on. The pump action has eased up, and I can now reach an indicated 190 bar fill… but what causes the lube and moisture dump to go brown… I don't know.
Back to the previous concern: it was disturbing to pump to an indicated 190 bar and then discover that the first shots with Crosman Premiers were down to 8.3fp. It took quite a few shots to get the rifle back up to optimum. I needed to check the indicated pressure against another system. Brad Troyer kindly lugged his SCUBA tank out to the shooting range and we managed to connect the S 200 and fill it to an indicated 180 bar. I then connected the rifle to the Hill pump and it indicated 170 bar. Thanks Brad, it was a hot day to be hauling a SCUBA tank around.
It seems that the gauge on my pump is indicating 10 bar below actual pressure.
Without a laboratory standard pressure gauge to calibrate against, do not always accept the indicated pressure and the manufacturers' recommendation as being absolutes. I now firmly believe in using a chronograph of some kind to establish the maximum indicated fill pressure on your pump, or adapter hose, that your gun will accept before muzzle energy drops off at the top end. Then mark that on your fill system gauge as your maximum fill pressure.
My final gripe with the Hill pump is that it is heavy, weighing in at almost 7lb 7oz. (3.37kg) and the outer tube is fixed to the handle. This conceals the pump rod and protects it from dirt, but whenever I pick up the pump by the handle or the outer tube, the base unit slides towards the floor. It's tricky to carry. A spare duffel bag is needed just for the pump… and perhaps a spanner to fit and remove the filling hose because it won't bend out of the way if left on the pump. Some sort of restraining clip on the bottom of the pump tube to lock it in place for carrying would be nice.
The Hill is a good pump, but the convenience details do bother me. I recommend purchasing a spare air reservoir for the CZ 200 and packing that instead of the pump or SCUBA tank to take on all but the longest expeditions.
Synopsis
If you are considering your first pre-charged pneumatic air rifle, or are looking for a handy second rifle, then the CZ 200 / Air Arms S 200 / Daisy Avanti is not only worth a look, it could be on the top of the list. It offers amazing accuracy and value from the combined efforts of CZ and Air Arms, with input from Daisy. A truly modern, international, air rifle. From all reports in the UK, it is rapidly becoming a classic and has outsold all expectations; it is easy to see why.
ciao
Fabio
fatta in fretta e furia
aspetto l'articolo completo
molto bella..... 
appena ti arriva un bel cartellino da br così vediamo di cosa è capace
