.221 Remington Fireball

.221 Remington Fireball
Type	Pistol / Rifle
Place of origin	United States
Production history
Designer	Remington / Wayne Leek
Manufacturer	Remington
Produced	1963
Specifications
Parent case	.222 Remington
Case type	Rimless, bottleneck
Bullet diameter	.224 in (5.7 mm)
Neck diameter	.253 in (6.4 mm)
Shoulder diameter	.361 in (9.2 mm)
Base diameter	.376 in (9.6 mm)
Rim diameter	.378 in (9.6 mm)
Rim thickness	.045 in (1.1 mm)
Case length	1.400 in (35.6 mm)
Overall length	1.830 in (46.5 mm)
Rifling twist	1-12 in (300 mm)
Primer type	Small rifle
Maximum CUP	52,000 CUP
Ballistic performance
Bullet mass/type Velocity Energy 45 gr (2.9 g) SP – Pistol 2,947 ft/s (898 m/s) 868 ft⋅lbf (1,177 J) 50 gr (3.2 g) SX – Pistol 2,813 ft/s (857 m/s) 879 ft⋅lbf (1,192 J) 55 gr (3.6 g) SBT – Pistol 2,700 ft/s (820 m/s) 891 ft⋅lbf (1,208 J) 45 gr (2.9 g) SP – Rifle 3,203 ft/s (976 m/s) 1,025 ft⋅lbf (1,390 J) 55 gr (3.6 g) SBT – Rifle 2,950 ft/s (900 m/s) 1,063 ft⋅lbf (1,441 J)
Test barrel length: 14 in (360 mm), 24 in (610 mm) Source(s): Accurate Powder[1]

The .221 Remington Fireball (5.7x35mm), often simply referred to as .221 Fireball, is a centerfire cartridge created by Remington Arms Company in 1963 as a special round for use in their experimental single-shot bolt-action pistol, the XP-100.^[2] A shortened version of the .222 Remington, it is popular as a varmint and small predator round while also finding use among target shooters. It has application as both a pistol round and as a rifle round.