.243 Winchester

.243 Winchester
.243 Winchester cartridge
Type	Rifle
Place of origin	USA
Production history
Designer	Winchester
Manufacturer	Winchester
Produced	1955
Variants	.243 Winchester Improved (Ackley)
Specifications
Parent case	.308 Winchester
Bullet diameter	.243 in (6.2 mm)
Neck diameter	.276 in (7.0 mm)
Shoulder diameter	.454 in (11.5 mm)
Base diameter	.471 in (12.0 mm)
Rim diameter	.473 in (12.0 mm)
Case length	2.045 in (51.9 mm)
Overall length	2.7098 in (68.83 mm)
Case capacity	52 or 53 to 54.8gr H2O
Rifling twist	1-10 to 1-8
Primer type	Large Rifle
Maximum pressure (SAAMI)	60,000 psi (410 MPa)
Ballistic performance
Bullet mass/type Velocity Energy 55 gr (4 g) BT 4,058 ft/s (1,237 m/s) 2,012 ft·lbf (2,728 J) 65 gr (4 g) BT 3,746 ft/s (1,142 m/s) 2,026 ft·lbf (2,747 J) 75 gr (5 g) HP 3,447 ft/s (1,051 m/s) 1,979 ft·lbf (2,683 J) 90 gr (6 g) SP 3,203 ft/s (976 m/s) 2,051 ft·lbf (2,781 J) 105 gr (7 g) BT 2,986 ft/s (910 m/s) 2,080 ft·lbf (2,820 J)
Source(s): Hodgdon http://data.hodgdon.com/cartridge_load.asp

The .243 Winchester (6×52mm) is a popular sporting rifle cartridge. Initially designed as a varmint round, it may be used for wildlife and game such as coyote, blacktail deer, whitetail deer, mule deer, pronghorn, and wild hogs. It can also be used against larger game such as black bear or elk, but is sometimes said to be "too light" for such large game. Rounds of at least 90 grains are better suited for hunting larger game while rounds less than 90 grains are more suitable for varmints. The .243 is based on a necked down .308 cartridge case.

This cartridge was first introduced in 1955 for the Winchester Model 70 bolt-action and Model 88 lever-action sporting rifles and quickly gained popularity among sportsmen worldwide. Just about every major manufacturer offers rifles chambered in .243.

It was a ground-breaking development of the day, combining a very useful combination of lightweight (70 to 85 grain) bullets optimized for long-range performance for varmint hunters (groundhogs, coyotes, prairie dogs) and 90 to 105 grain bullets suitable for game up to the size of deer and pronghorn antelope. Its predecessor in the Winchester line-up, the very similar .257 Roberts, could have easily been selected to accomplish the same tasks, but was not available factory loaded with either lighter, varmint-weight pills or pointed, long range spitzer (pointed) bullets, so it never achieved the popularity of the newer round.

Remington also saw the 6mm (.243") family as suitable for this dual-purpose use and introduced their version, the .244 Remington, in the same year (1955) based upon the .257 Roberts necked down to accept .243 bullets up to 90 grains in weight. The Winchester round remains available today whereas the .244 Remington, later renamed the 6mm Remington with the introduction of 100 grain bullets, is far less popular even though it can push all bullet weights slightly faster with maximum loads due to the larger capacity case. The fact that the .243 Win was originally offered in a 1 in 10" rifling twist rate, a rate better able to stabilize heavier 100 and 105 grain bullets, versus the .244 Remington's 1 in 12" twist (hence the 90 grain factory offering) was also a factor in their popularity.