(AO) - In
scopes, the front objective turns to focus the image. Most AO
scopes also have yardage ticks to rangefind while focusing.
Airgun Rated (Scopes) - Can mean one of two things: 1)Built strong enough to handle a heavy recoiling spring gun, which recoils both rearward and forward, which is more harmful to scopes that high-power firearms. or 2)Built to focus down to closer ranges than a typical firearm scope, normally about 10 yards as a minimum.
BAR vs PSI (Air Pressure) - Two standards of measurement for pneumatic pressure. 1.0 BAR is equal to 14.5037738 PSI. So, 200 BAR x 14.5037738 is equal to 2900.75 PSI. To convert PSI back to BAR, divide by 14.5037738.
Dieseling - When a spring piston airgun has excessive lube, and this lube ignites due to the heat caused by the rapid increase in air pressure during the piston compression stroke. This process is normal on a new or recently lubricated spring gun. Excessive dieseling can be cause for concern as seals and/or components can be damaged.
Gas Ram - Similar to a spring gun in function, without the mainspring. A gas ram is a gas strut placed in the compression chamber of the rifle. Behind the piston is compressed air. When the airgun is cocked, the air is further compressed. When the airgun is fired the air expands and pushes the piston forward, compressing the air in front of the piston and thus fires the pellet.
M.O.A. - Acronym for Minute of Angle. Minute of Angle is defined as the distance of a line that is made from point A to point B of an angle of one minute of one degree at a distance of 100 yards. More simply stated, Minute of Angle is movement of 1 inch at 100 yards. A scope with 1/4" MOA will shift 1/4" of movement at 100 yards for every click of the turret. Target scopes have finer adjustments with 1/8" MOA, allowing for 1/8" of movement per click at 100 yards.
Moderator - A device designed to reduce muzzle report on an airgun by moderating the air released when firing.
Parallax - Dictionary says: An apparent change in the direction of an object, caused by a change in observational position that provides a new line of sight. Practical definition: Cross-hair picture moves off target depending on head placement. Focusing the scope properly can eliminate parallax and improve accuracy by eliminating the error in head placement.
Precharged - Any airgun that requires gas to be transfered to an onboard tank to generate its power.
Pneumatic - Any airgun that uses compressed gas as its powerplant. Examples would be Precharged, Single-Stroke, and Pump-up.
Regulator - Device that steps the pressure in the air cylinder down to a lower level to maintain consistent pressure for the airgun to fire from. Often found on match grade rifles to ensure absolute consistency.
Single Stage Trigger - Typical American hunting trigger that breaks upon application of pressure.
Target Turrets - Raised adjuster knobs on a scope that can easily be turned by hand without use of tools.
Two Stage Trigger - Small amount of take up is the first stage, coming to a complete stop. Second stage breaks and releases trigger with any further pressure.
Underlever - Any airgun where the cocking lever is seperate from the barrel and located beneath the barrel. Most run parallel with the barrel, but some are inside the stock.
Velocity - The speed at which the ammunition is being propelled. Normally calculated as Feet-Per-Second (fps).