Prism sight
A prism sight or prismatic sight, sometimes also called prism scope or prismatic scope, is a type of
Description
Prism sights are a type of
Magnification
Prism sights often have fixed low-power
There are prism sight designs with variable magnification, such as the
Reticle
Like telescopic sights, prism sights have an etched
Diopter
Prism sights usually have
Parallax
Prism sights have a somewhat larger parallax error than red dot sights. Usually, they do not have an adjustable parallax like some telescopic sights.[1]
Eye relief
Another disadvantage is eye distance.[2] Like telescopic sights, the eye must be within a certain distance from the scope.
History
Prisms have been used in binoculars since the 1890s.[3] During World War I, the US Army chose to equip the M1903 Springfield repeating rifle for the sniper rifle role by mounting a sight similar to half a binocular, a prismatic sight developed by the Warner & Swasey Company.[4] It was a short and compact sight, and the prisms allowed the objective to be angled to the side so that the 1903 rifle could be loaded with a clip from above. It was still possible to use the iron sights with the scope mounted.[4]
The M1908 version of the scope had 6-times magnification, while the later M1913 version had slightly less magnification at 5.2×. The background for choosing a lower magnification was a larger field of view and improved light transmission.[4] The sight was constructed of steel and brass, was painted black inside for optical performance, and had a relatively high mass of 1,020 g (36 oz).[4] The eye relief was only 38 mm (1.5 in), so the sight was equipped with a rubber eyepiece shield to prevent the scope from hitting the face during recoil. The reticle was a thin crosshair, as was common for this time period.[4]
These sights were fitted to the Hotchkiss M1909 Benét–Mercié machine gun.[5] Canadian Forces ordered 500 samples of the 5.2× variant.[6] Moisture on the inside of the lenses was one of several problems in the field,[6] and the scope was known to loosen.[7][8] In total, approximately 8,000 units of these prismatic sights were produced. The scope sight had the greatest magnification of the First World War, but in return only had a 4.5 degree field of view.[6]
A well-known later example is the fixed-magnification Trijicon ACOG which has been used in combat by the US Marine Corps, US Army and USSOCOM.[9]
In the 2010s, several manufacturers including Trijicon, and Vortex began offering prism sights on the consumer market.
In October 2019, the Chinese QBZ-191 automatic rifle was revealed at the 70th Anniversary National Day military parade. It has a 3× daylight prismatic sight called QMK152 and QMK-171A.
See also
- holographic sightor prism sight
- Low-power variable optic, a variable-zoom telescopic sight with magnification range from 1x to no more than 10x
References
- ^ NRA Blog | Red Dots 101: Understanding the Types of Sight Systems
- ^ "Red Dots 101: Understanding the Types of Sight Systems". Retrieved 2022-08-08.
- ^ "History of Telescopes and Binoculars - Proc. of SPIE Vol. 8129 81290S-13" (PDF).
- ^ a b c d e "SPRINGFIELD M1903 WWI SNIPER RIFLES". 2020-03-31. Retrieved 2022-08-08.
- ^ McCollum, Ian (2015-12-02). "M1903 Sniper Rifle with Warner & Swasey M1913 Musket Sight at RIA". Retrieved 2022-08-08.
- ^ ISBN 978-1-4728-5079-9.
- ^ "Warwickshire Armourers Rifle and Pistol Club | Springfield M1903 with the Warner & Swasey telescopic sight – Model 1908 and 1913". Retrieved 2022-08-08.
- ^ Optics, Hi-Lux. "An Early History of Rifle Scopes, 1776-1930". Retrieved 2022-08-08.
- ^ Low Power Variable Optic vs. Prism Scope for Your Budget AR-15