AR-15

name=AR-15

Technical data

• Caliber: .223 Rem, 5.56 x 45 mm NATO (many variants in other calibers are made by various manufacturers)
• Length: 39 in (991 mm)
• Mass: 3.4 kg (7.5 lb)
• Barrel: 20 in (508 mm) standard, 16 in (406mm) and 14.5(368mm) common
• Rifling: 1:12 for original 55 grain (3.6 g) bullets. Newer configurations use 1:9 and 1:7 twist rates. There is much controversy and speculation as to how differing twist rates affect ballistics and terminal performance with varying loads, but higher bullet weights tend to perform better with steeper rifling rates.
• Magazine capacity: 10, 20, 30; 90, 100 (see below)

Standard issue magazines are 20 or 30 round double stack magazines; drum magazines in 90 and 100 round capacities also exist. Low-capacity magazines are available to comply with some areas' legal restrictions or for hunting.

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