Thursday, April 29, 2010

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Monday, November 2, 2009

Limited Time Offer for Walther PPK/S CO2 Pistol

Limited Time offer.

Icludes: Walther PPK/S CO2 Pistol , 7 CO2 Cartridges, 600 Steel BB's.

Walther PPK, James Bond sidearm, has a lot of fans. And Umarex Walther PPK/S CO2 BB Pistol replica is made for them.

This Semiautomatic pistol has a Single-action mechanism and a magazine for 15 BBs.
The main feature of this gun is its authenticity: solid cast metal with elegant blued finish. This replica is both true to size and true to weight (may be an ounce lighter than a real pistol). Besides this air gun has a very realistic blowback action and recoil.
Per one CO2 cartridge you will be able to make approximately 60 shots (an average figure but considering that CO2 is used for blow-back action, it’s rather good).
This gun has a short non rifled barrel that does not allow it to have extraordinary accuracy or velocity (it is about 300 FPS). But it is great for fun, plinking and practicing how to handle firearms.


Wednesday, September 23, 2009

Physics of CO2 Gun: Myths & Reality

Looking through the web sites, forums and blogs devoted to Air Guns we see that users have a lot of questions concerning CO2 guns functioning. And we also notice that there is a lot of information that is not true. For example a person who was interested in Drozd CO2 BB pistol asks an air gun store manager if the muzzle velocity will decrease with every shot. A seller answers that it definitely will, because with every shot the amount of CO2 remaining in the cartridge became less. When I hear statements like this I want to become a writer (at least for a while) and to explain other people what really happens.

So, why the muzzle velocity will not drop?
CO2 guns and pistols are powered by CO2 (carbon dioxide). Notwithstanding a cartridge kind, volume and manufacturer it carries liquefied CO2. The liquid fraction constitutes 80% of CO2 gas in a new sealed cartridge (unless the cylinder was underfilled). 20% of volume is a gas fraction.

Pressure of gaseous CO2 depends on the temperature inside a cylinder (that is usually equal to ambient air temperature). Energy of this pressurized gas is used to power CO2 pistols and rifles. When a portion of gas is spent for a shot a portion of liquefied CO2 turns into equal amount of gas immediately. And interior pressure in a cylinder remains the same. And this process keeping pressure at the same level for quite a long time continues till there is no more liquefied fraction of CO2 in a cartridge. Before this point pressure of gas can be considered as constant. This effect of pressure self-stabilization allows using CO2 to power Air Rifles and Pistols including ones designed for shooting sport.

When all liquefied CO2 is spent some gas will remain in a cylinder and its volume will be equal to volume of a cartridge. After reaching this point the pressure inside the reservoir drops very quickly. It is recommended to waste the rest of gas shooting without pellets before removing a cylinder. If you continue to shoot with pellets there is a risk of pellets jamming inside a barrel because pressure becomes so low that it is not enough to let a projectile leave a barrel. If you do not dry-fire a pistol or a rifle before removing a cylinder a low temperature of CO2 gas escaping from a cartridge when you are taking it away will damage rubber seal. So you will have to change rubber o-rings in order to prevent leakage.

Now let’s try to think how many shots per one cylinder we will have. At atmospheric pressure one liter of CO2 weighs 1.98 gr. So we will get about 6 liters out of 12 gr. reservoir. According to Boyle-Mariotte law for a given mass of gas multyplicating volume by pressure we will get a constant figure (providing the temperature does not change).
P1 x V1=p2 x V2=…const (t=const, m=const)
So at room temperature and 60 bar pressure we will get 99 cc of CO2. Now we deduct 15 cc (a volume a cylinder), that will be spent for the last 10-20 shots without pellets (that we have already mentioned).
This 84 cc will give an energy for full-power shots, that we will make till some liquefied gas remains in a cylinder.

Now, how much gas is needed for one shot? Barrel pressure (a pressure that force a projectile to leave a barrel) is 20-40% of maximum pressure. Knowing a barrel length we can calculate its volume, for example a volume of 6’’ barrel is about 1.5 cc. So, for one cartridge we will have
84cc : 1.5cc=56 shots.

Using Boyle-Mariotte law we can calculate that at 32oF and 30 bar pressure we will have 264 cc of CO2 and twice more shots but their power will be twice less. Under these conditions it will be useless to change a cartridge after a couple of clips, it will not make shots more powerful.
But still when we shoot very quickly we notice that velocity drops. Why does it happen? The matter is that a process of turning liquid fraction into gaseous one demands some heat energy (so-called heat-absorbing process). When you shoot very quickly a temperature inside a cylinder drops, heat energy is not enough and the process of turning liquid into gas slows down.

Thus pressure of every new portion of gas will be lower than pressure of a previous one. In order to prevent this effect it is necessary to make intervals between shots enough to restore a temperature inside a cylinder till air temperature level. Some authors say that when you shoot quickly a pressure inside a cylinder decreases because there isn’t enough time to turn liquefied fraction into gaseous one. But this is not right.

Muzzle velocity depends on gas pressure, volume of gas portion and distance at which a power is affecting a projectile (barrel length). So the fastest velocity will have a gun with longer barrel providing temperature being equal and a portion of gas is optimal for this gun.
Optimal portion of gas allows achieving a high velocity while a volume of spent gas being acceptable. There is also a maximum portion of gas that moves a pellet with a maximum velocity for a given barrel. For example if optimal portion of CO2 will force a projectile to leave a barrel at 360 fps and we will have 40-45 shots per one cartridge, with maximum portion of gas a muzzle velocity will be 380-385 fps and a cartridge will be enough for 25-28 shots. Further increasing of gas portion will give nothing. At the same time if we will take longer barrel, for example 8” instead of 6” a velocity will be 50-65 fps more (gas portion being the same).
It is impossible to achieve such a result by increasing a portion of gas.

Air Gun Maintenance

Careful and, what is more important, regular maintenance is the main condition of reliable Air Gun functioning and safety. There are several basic rules every airgunner should follow.

Never keep your Spring-Piston Air Guns cocked. It causes spring fatigue, thus you will have to change a spring rather often.
If you have charged your CO2 Air Gun with a CO2 cartridge do not keep it charged more than 2 weeks (24 hours is recommended).Rechargeable air-cartridges may serve for a month. Then a day or two are necessary to restore the original form and elasticity of rubber seal.
Using a high-power rifle do remember to tighten all screws that tend to unscrew after 30-40 shots.

Never drop or hit your Air Gun. Many important components of Air Rifles and Air Pistols are often made of silumin (a kind of aluminum alloy) and other fragile materials. Plastic details and wood stocks can also be broken.

It is not recommended to use low-quality cheap pellets, improper or handmade pellets, because they may be jammed in the barrel. Jamming of several pellets may cause an irreversible damage of a rifled barrel after the barrel is cleaned with a ramrod.
Cocking a rifle with a Break Barrel Action hold the barrel with one hand and the butt stock with the other hand. Do not cock it with a jerk carrying the rifle in one hand (in the way cinema heroes do). Move all the levers smoothly with necessary effort. Do not apply excessive effort moving a trigger, a cock or levers. .

Very often if you pull a trigger when your Air Gun safety is “ON SAFE” position you can seriously damage percussion trigger unit.
With the course of time pellets tend to jam in rotary magazines. In this case pulling the trigger with unnecessary effort you can damage a gun.

Some shooters use oil, gasoline or ether in order to increase muzzle velocity. They drop a liquid into the working chamber or inside a pellet itself. When the gun shoots a momentary pressure growing in air chamber leads to oil inflaming that becomes a source of additional energy affecting a projectile (so-called a “dieseling” effect). However combustion products remain in a cylinder and other parts and spoil a piston mechanism. In order to avoid negative consequences of “dieseling” in Spring-Piston Guns it is recommended to use the minimum quantity of oil (a drop or two) and load a rifle with lightweight pellets or felt wadding for the fist three or four shots after oiling. There are also special gun oil with graphitic, molybdenic and silicone additive agent that do not cause a “dieseling effect”.

Do never dry-fire your Spring Piston Air Gun. For a powerful “Magnum” class Air Rifles choose heavy-weight pellets (0.6 gr. and more).

Be careful charging CO2 rifles with CO2 cartridges. Do remember that pressure of leaking gas is 60 bar and the temperature is -94˚ F. Remove and install CO2 cartridges according to manual. For example for installing a cartridge, firstly put a cylinder into a grip then tighten a piercing knob towards CLOSE thus piercing cartridge membrane. For removing a CO2 cylinder turn a piercing knob towards OPEN, until you hear gas start to escape, continue turning the knob, remove a backstrap and drop out a CO2 cylinder. Construction of CO2 device and the actions may be different but the main principle is the same: do not come in contact with the escaping gas.

If the quantity of shots per one CO2 cartridge decreases with the course of time, it may indicate gas leakage. Probably it is time to change o-ring or CO2 feeder unit.
A regularity of examination and cleaning of Air Guns is not as critical as in case of firearms. But proper maintenance will guarantee a long life of your Air Gun. Clean your gun after buying in order to remove factory conservation oil, clean it after shooting and after staying outdoors. If there is a condensate on a gun dry it with a piece of cloth before cleaning. Oiling the gun follow instruction of the manual.

Usually it is not necessary to disassemble a pistol or a rifle before cleaning. If it is necessary to do it follow the user guide. If you are not experienced enough ask an airgunsmith to repair or clean your Air Gun.

Examine the gun before cleaning, if there are any defects of metal and wood parts, unscrewed bolts, rust etc. Then oil the critical points of air compression system, rubber and synthetic rings, piston cup and compression chamber. Make several shots in order to spread the oil inside the mechanism. Use special hard oil for springs of Spring-Piston Air Guns. Oil barrels of powerful (magnum class) rifles after every 40-50 shots otherwise it will shoot less accurately. In CO2 guns oil sealing o-rings after every shooting or changing every third cartridge. Oil the percussion trigger unit after 1500-2000 shots. Oil all the levers and piercing knob of CO2 gun when it is necessary. Wipe the gun. Finely use neutral oil and wipe all the metal components one more time with a piece of cloth. Do never oil wood stock.


UMAREX Smith & Wesson 586/686

If you have ever seen UMAREX Smith & Wesson 586/686 or if you were lucky to shoot or own it you will agree that it is one of the best CO2 revolvers ever made.

UMAREX (a company owned by Walther) is a well-known German manufacturer of quality CO2 pistols replicating famous firearms. But in case with Smith & Wesson 586/686 UMAREX managed to outdo itself. The manufacturer tried to do its best making a pellet copy very close to the original precisely copying its design, dimensions and weight (UMAREX replica weighs 60-100 gr. less than the real thing).

The difference between 586 and 686 model is in finishing: 586 is black and 686 is nickel. I prefer a nickel version, because 586 is not blued but painted, it is a bit too shiny and looks rather unnatural. Besides I doubt that this coating is durable. UMAREX Smith & Wesson 586/686 comes with barrels of different length (4" (101,6 mm), 6" (152,4 mm) и 8" (203,2 mm)). If you know something about CO2 gun ballistics you understand why a 4” version is not very powerful (it will suit for plinking or fun), a 6” barrel is a bit more effective than average CO2 pistol. With an 8” barrel we can expect a good velocity and power, more flat trajectory and accuracy, so it will be good for small game hunting and pest control.

Construction of Smith & Wesson 586/686 allows changing barrel easily and quickly. You can buy 2.5", 4", 6" or 8" barrel and shrouds; a plastic wrench used for barrel replacement is included in the package. But we do not recommend changing barrels very often because a screw thread made of silumin tends wear out. A pistol has a quality steel barrel with 6 grooves.
A 10-shot rotary clip is made of aluminum alloy. It is one of the most disputable thing about 586/686. It isn't as long as a firearm cylinder and some people do not like it. Both versions have a black clip that looks very odd at a nickel 686. A pellet is fixed well in a chamber of a clip. Buying a gun check concentricity adherence of a clip and barrel (some UMAREX pistols has a slight defect of this unit that influence velocity and accuracy).

UMAREX Smith & Wesson 586/686 comes with metal front and rear sights, rear sights are adjustable for windage and elevation, it is a square notch similar to one of firearms though made of different materials. Eight-inch barrel separates the sights farther for more aiming precision, hence more accuracy. It is possible to use a dovetail rail for a scope or a red-dot sight instead of rear sight. Front sight is also removable; a black one can be replaced with an orange, blue or ivory sight for better aiming. You may also mount a rifle scope and a butt stock turning a pistol into some kind of a carbine.

A pistol works perfectly. If you want you your S & W to shoot better clean the gun after buying in order to remove factory conservation lubricant and then oil a pistol with gun oil. 586/686 shoots both in single-action and double action mode. Single-action trigger pull is good enough. Double-action trigger-pull is smoother and allows shooting more accurately. By the way this S & W shows a very good accuracy for a CO2 pistol. I got group less than one inch at 10 meters. It is the best result among all the other repeating air pistols.

The only serious drawback of UMAREX Smith & Wesson 586/686 is that many important components (for example a trigger, a hammer catch and a cock) are made of silumin. That is why a pistol that works like a dream at the beginning operates not so smoothly after 1000 shots and a trigger starts to play that irritates much. Though changing of worn detail will solve all the problems it is possible only in those countries where UMAREX has its service centers (US being among the lucky ones) otherwise it will be difficult to repair a pistol.

Smith & Wesson 586/686 is powered by 12gr. CO2 cylinders. A construction of CO2 unit is typical for UMAREX. One CO2 cylinder will be enough for 60 full-power shots at 73 o -77 o F. Further shooting is not effective because a trajectory of a projectile changes significantly from shot to shot. The first 40-50 shots are good enough for hunting. From 10th to 40 th shot a trajectory is almost absolutely stable (providing ambient temperature is constant). Accuracy is in direct proportion to barrel length. An 8” barrel shows perfect muzzle velocity and accuracy for this type of gun.
UMAREX Smith & Wesson 586/686 Specification
Barrel length 4” 6” 8”
Overall length 9.25” 11.22” 13.18”
Weight 2.49 lb 2.75 lb 3.08 lb
Caliber .177”
Ammo Lead pellets only
Powerplant 12-gr.CO2 cylinder

Sunday, September 13, 2009

Airgunstyle AirBlog: Types of Airguns

Airgunstyle AirBlog: Types of Airguns

Airgunstyle AirBlog: Choose Your Ammo Right

Airgunstyle AirBlog: Choose Your Ammo Right