parallax
In telescopic and dot sights, parallax describes the perceived movement of the reticle in relation to the shooter's head. In short, if a shooter aims through a telescopic or dot sight, then moves their head (but not the rifle) from side to side, they may see the reticle move. This is bad news, because unless the shooter's head is in the exact same position each time they take aim, point-of-aim will shift and the shots will not be accurate.
Unfortunately, the only way to fix parallax is to spend money on it. Quality dot sights can reduce parallax to the point where it is unnoticeable, as long as the sight is not magnified. In case you were wondering, that is one of the big differences between the $30 sight and the $600 sight. Telescopic sights, on the other hand, are magnified and therefore must have special features implemented to deal with parallax. Quality telescopic sights will feature parallax adjustment, which allows the shooter to adjust the parallax setting to match the range of the shot. If the shooter is about to take a 200m shot, they simply set the parallax adjustment to 200m, and parallax is eliminated. If the shooter then decides to take a 600m shot, the parallax setting must be re-adjusted or the reticle may shift. However, many scopes do not feature parallax adjustment and are instead designed to be parallax free at a certain range, usually the range where the scope is intended to be used most. Rimfire scopes, for example, as usually parallax-free at 50 yards, whereas centerfire hunting scopes are usually parallax-free around 200-300 yards.
Unfortunately, the only way to fix parallax is to spend money on it. Quality dot sights can reduce parallax to the point where it is unnoticeable, as long as the sight is not magnified. In case you were wondering, that is one of the big differences between the $30 sight and the $600 sight. Telescopic sights, on the other hand, are magnified and therefore must have special features implemented to deal with parallax. Quality telescopic sights will feature parallax adjustment, which allows the shooter to adjust the parallax setting to match the range of the shot. If the shooter is about to take a 200m shot, they simply set the parallax adjustment to 200m, and parallax is eliminated. If the shooter then decides to take a 600m shot, the parallax setting must be re-adjusted or the reticle may shift. However, many scopes do not feature parallax adjustment and are instead designed to be parallax free at a certain range, usually the range where the scope is intended to be used most. Rimfire scopes, for example, as usually parallax-free at 50 yards, whereas centerfire hunting scopes are usually parallax-free around 200-300 yards.
Parkerizing (phosphating, phosphatizing)
Around World War II, Parkerizing replaced bluing as the preferred method of firearm rust prevention before being itself replaced by even more modern passivation (rust-prevention) techniques. Like bluing, Parkerizing involves submerging the steel in a chemical bath, but instead of the smooth shine of a blued finish, Parkerizing produces a dull, textured finish that ranges in color from light gray to black. Parkerizing also creates a layer of microscopic "hills and valleys," providing superior oil retention over blued or bare steel and making a superb basecoat for paint or enamel. Note that although Parkerizing provides better baseline rust prevention than bluing, it should still be combined with an oil for maximum protection.
PDW (Personal Defense Weapon)
A PDW is a highly compact long gun that fires small, lightweight, high-velocity rounds intended to defeat personal body armor. The PDW class of weapons emerged in response to the widespread availability of modern body armor, which is able to defeat the pistol rounds fired by submachine guns. With SMGs no longer able to reliably neutralize enemy targets, the only alternative was the comparatively large, loud, and heavy carbine, until the rise of the PDW. PDW cartridges resemble scaled-down rifle rounds (narrow and fast) rather than pistol rounds (wide and slow), and are thus able to defeat body armor at close range, but PDW rounds sacrifice the long-range enthusiasm of true rifle rounds in favor of low recoil and small size.
The FN P90 and the H&K MP7 are two of the most well-known PDW designs.
The FN P90 and the H&K MP7 are two of the most well-known PDW designs.
pistol carbine
A pistol carbine is the civilian equivalent of a submachine gun: a long gun firing pistol-caliber ammunition, usually from high-capacity magazines.
Pistol carbines are popular among both civilians and police. For more information, see this article.
Pistol carbines are popular among both civilians and police. For more information, see this article.
piston-driven, gas-piston
These terms are slang for a gas-operated firearm action, and are usually used when describing AR-pattern rifles that have been converted to gas-operation, rather than using the traditional gas-expansion system originally designed for the AR.
plinking
Plinking is a term for shooting without a specific goal in mind, in other words, shooting just for the fun of it. The name comes from the sound a bullet makes when it hits an aluminum can. Coins, spent shotgun shells, and balloons are also common plinking targets, though any piece of debris will do.
"Plinking ammunition" is inexpensive ammunition with average accuracy and power, often sold in bulk quantities. Plinking ammunition and target ammunition are synonymous terms; high-quality, precision-made ammunition is called match-grade ammunition.
"Plinking ammunition" is inexpensive ammunition with average accuracy and power, often sold in bulk quantities. Plinking ammunition and target ammunition are synonymous terms; high-quality, precision-made ammunition is called match-grade ammunition.
POA (point-of-aim)
POA is an acronym for point-of-aim, and refers to the focal point of a firearm's sighting system. If the POA and the POI (point-of-impact) are not the same, the POA can be shifted by adjusting the firearm's sights.
POI (point-of-impact)
POI is an acronym for point-of-impact, and refers to the the area where a bullet will land. If the POA (point-of-aim) and the POI are not the same, the POA can be shifted by adjusting the firearm's sights.
POSP
POSPs are a series of telescopic sights manufactured by BelOMO. POSP sights are (or were) used by Russian military and law enforcement, though exactly which models have been chosen for service over the years is a matter of debate in the USA.
POSP sights receive mixed reviews in the United States, with some citing excellent glass quality and overall fit and finish, while others claim POSP sights are sub-par compared to Western or Asian optics at similar price points. POSP sights have also had difficulty finding acceptance with American shooters due to their AK and SVD side-mount designs, but Weaver-compatible versions are popping up more and more frequently. Additionally, it is generally agreed that POSP sights are unusually sturdy and robust for their price point.
Care should be taken not to confuse POSP sights with PSO sights. Although PSO and POSP sights have both been issued to the Russian military in the past, POSP sights are not confirmed to be in current issue. Additionally, PSO sights are made in Russia by NPZ whereas POSP sights are made in Belarus by BelOMO. Additionally, POSP sights are available with Weaver-compatible bases, while PSO sights are not.
POSP sights receive mixed reviews in the United States, with some citing excellent glass quality and overall fit and finish, while others claim POSP sights are sub-par compared to Western or Asian optics at similar price points. POSP sights have also had difficulty finding acceptance with American shooters due to their AK and SVD side-mount designs, but Weaver-compatible versions are popping up more and more frequently. Additionally, it is generally agreed that POSP sights are unusually sturdy and robust for their price point.
Care should be taken not to confuse POSP sights with PSO sights. Although PSO and POSP sights have both been issued to the Russian military in the past, POSP sights are not confirmed to be in current issue. Additionally, PSO sights are made in Russia by NPZ whereas POSP sights are made in Belarus by BelOMO. Additionally, POSP sights are available with Weaver-compatible bases, while PSO sights are not.
primer
A primer is a small metal cap containing impact-sensitive explosive. Primers are inserted at the base of a cartridge or shell, and are struck by the firearms firing pin to generate a shower of sparks that ignites the cartridge's propellant and fires the bullet. There are two common types of primers, Berdan primers and Boxer primers, with Boxer primers being far more common in the USA.
profile, barrel profile
Barrel profile refers to the external contours of a barrel. Very few barrels are pure cylinders from end to end, though bull barrels often come close. Thick barrels tend to provide better rigidity and heat dissipation, and thus are usually more accurate for repeated firing. Thin barrels tend to vibrate more and have less surface area to dissipate heat, so they tend to lose accuracy under repeated firing as the barrel expands and softens very slightly as it heats up. Stepped contours vary the thickness of the barrel at different points, usually beginning with the thickest portion at the chamber and progressively thinning to the muzzle, though some barrels have weighted muzzles to control recoil or affect barrel harmonics.
PSO (PSO-1, PSO-1M2)
PSO is a Russian acronym for Pritsel Snaipersky Optichesky, or "Optical Sniper Sight" in English. The PSO sights are a series of telescopic sights issued in the Russian military, usually found on long-range rifles like the SVD and SV-98. PSO sights do not use scope rings, instead having an integral scope mount machined into the scope body that mates with the side-mounted scope rail on SVD and AK-pattern rifles.
PSO sights receive mixed reviews in the United States, with some citing excellent glass quality and overall fit and finish, while others claim PSOs are sub-par compared to Western or Asian optics at similar price points. Additionally, the PSO series' unique integral scope mount means they cannot be mounted on standard Weaver or Picatinny rails, further reducing their popularity. However, it is generally agreed that PSO sights are unusually sturdy and robust for their price point.
Care should be taken not to confuse PSO sights with POSP sights. Although PSO and POSP sights have both been issued to the Russian military in the past, only PSO sights are confirmed to be current, military issue sights. Furthermore, PSO sights are made in Russia by NPZ whereas POSP sights are made in Belarus by BelOMO. Additionally, POSP sights are available with Weaver-compatible bases, while PSO sights are not.
PSO sights receive mixed reviews in the United States, with some citing excellent glass quality and overall fit and finish, while others claim PSOs are sub-par compared to Western or Asian optics at similar price points. Additionally, the PSO series' unique integral scope mount means they cannot be mounted on standard Weaver or Picatinny rails, further reducing their popularity. However, it is generally agreed that PSO sights are unusually sturdy and robust for their price point.
Care should be taken not to confuse PSO sights with POSP sights. Although PSO and POSP sights have both been issued to the Russian military in the past, only PSO sights are confirmed to be current, military issue sights. Furthermore, PSO sights are made in Russia by NPZ whereas POSP sights are made in Belarus by BelOMO. Additionally, POSP sights are available with Weaver-compatible bases, while PSO sights are not.
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