What is 243 Winchester? The 243 Winchester is a .243-caliber, rimless, bottlenecked rifle cartridge made by necking the 308 Winchester case down to 6 mm. Winchester introduced it in 1955, and it has been a standard deer, pronghorn and varmint cartridge since. It fires 55 to 105 gr bullets at about 2,900 to 4,000 fps with light recoil from a short action or an AR10. Chattahoochee Munitions manufactures the 243 Winchester on its CM10 large-frame semi-automatic platform with a 20-inch barrel in your choice of a 1:8 or 1:10 twist.

What Is 243 Winchester at a Glance

Specification	243 Winchester
Introduced	1955, by Winchester
Parent case	308 Winchester, necked down
Bullet diameter	.243 inch
Case length	2.045 inches
Cartridge overall length (SAAMI)	2.710 inches
SAAMI pressure limit	60,000 psi
Common factory bullets	55 to 105 gr
Published velocity	Hornady 90 gr ELD-X at 3,150 fps from a 24-inch test barrel
Chattahoochee Munitions twist	1:8 (416R stainless) or 1:10 (4150 CrMV) on the 20-inch CM10 243 Winchester

Cartridge and chamber dimensions are published in the ANSI/SAAMI centerfire rifle standard.

Where the 243 Winchester Came From

Three years after the 308 Winchester appeared, Winchester necked it down to 6 mm and introduced the 243 Winchester in 1955. One cartridge could fire light varmint bullets fast and heavier bullets for deer, from a short action with mild recoil. It is the oldest member of the 308 Winchester cartridge family and shares its bolt face with the 7mm-08, 338 Federal and 358 Winchester at Variant Valley.

What Is 243 Winchester Used For?

What is 243 Winchester used for? Deer, pronghorn, hogs, coyotes and varmints.

Deer and pronghorn: 90 to 100 gr expanding bullets with good shot placement. Read 243 for deer.
Coyotes and varmints: 55 to 75 gr bullets at 3,400 to 4,000 fps.
Feral hogs: 90 to 100 gr controlled-expansion bullets.
New and recoil-sensitive shooters: light recoil makes it easy to practice with.

Chattahoochee Munitions does not recommend the 243 Winchester for elk or bear. For elk, choose 338 Federal or 375 Raptor; for bear, 458 SOCOM XL or 375 Raptor.

What Is 243 Winchester Performance Like?

The 24-inch muzzle figure is Hornady’s published number. Downrange values and the 20-inch row are Chattahoochee Munitions calculations (published G7 BC 0.207, 200-yard zero, standard atmosphere, 10 mph full-value wind; 20-inch velocity estimated at 30 fps per inch below 24 inches). They are not chronograph data.

90 gr ELD-X	Muzzle	300 yd	500 yd	Drop at 500 yd	Wind at 500 yd
24-inch (published muzzle)	3,150 fps / 1,983 ft-lb	2,468 fps / 1,217 ft-lb	2,063 fps / 850 ft-lb	-36.7 in	19.8 in
20-inch CM10 (calculated)	3,030 fps / 1,835 ft-lb	2,362 fps / 1,115 ft-lb	1,967 fps / 773 ft-lb	-40.2 in	21.1 in

What Is 243 Winchester Twist Rate?

Many factory 243 Winchester rifles use 1:9.5 or 1:10, which stabilizes bullets up to about 100 gr. Chattahoochee Munitions offers both: the 1:10 4150 CrMV medium-contour barrel for 55 to 100 gr varmint and hunting bullets, and the 1:8 416R stainless SOCOM/HBAR barrel for heavier, long 105 to 108 gr bullets. Pick 1:10 if you shoot standard hunting and varmint ammunition, and 1:8 if you want heavy, high-BC bullets at distance.

Is 243 Winchester a Subsonic Cartridge?

No. Chattahoochee Munitions treats the 243 Winchester as a supersonic cartridge, and the CM10 243 is set up for supersonic ammunition with a flow-through suppressor rated for 6 mm. For subsonic shooting, look at 8.6 Blackout subsonic or 375 Raptor subsonic.

243 Winchester Compared With Other Cartridges

6mm Creedmoor vs 243 Winchester: two .243 cartridges, old and new.
243 vs 6.5 Creedmoor: 6 mm against 6.5 mm for deer and distance.
22 Creedmoor vs 243: .224 against .243 in the same CM10 magazine.
6mm ARC vs 243: the same bullets from an AR15.

243 Winchester Rifles From Chattahoochee Munitions

The CM10 243 Winchester uses a 20-inch barrel, either 416R stainless SOCOM/HBAR with a 1:8 twist or 4150 CrMV medium contour with a 1:10 twist, both with 5/8×24 muzzle threads and Tactical Grey Cerakote. It has rifle-length gas, a .750-inch Superlative Arms adjustable gas block, an Odin adjustable buffer, a TriggerTech Duty trigger and a B5 Systems CPS Medium stock. It weighs 9 lb 8 oz with an unloaded magazine and ships with one 10-round 243 Winchester magazine. Choose the 243 semi auto rifle in Black Tungsten, the 243 AR10 in Cobalt Kinetics Green Cerakote or the 243 AR rifle in FDE Metallic, browse CM10 243 Winchester AR10 rifles, or see the full Predator Plains lineup.

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What Is 243 Winchester FAQ

What is 243 Winchester made from?

The 308 Winchester case necked down to .243 inch.

Is 243 Winchester good for deer?

Yes, with a 90 to 100 gr expanding hunting bullet and good shot placement.

Is 243 Winchester good for elk or bear?

Chattahoochee Munitions does not recommend it for either. For elk choose 338 Federal or 375 Raptor; for bear, 458 SOCOM XL or 375 Raptor.

Is 243 Winchester the same as 6mm Creedmoor?

No. Both fire .243 bullets, but the 243 uses the 308 case and the 6mm Creedmoor uses the 6.5 Creedmoor case.

What twist rate should a 243 have?

1:9.5 to 1:10 for bullets up to about 100 gr; 1:8 for heavy, long bullets. The CM10 243 offers 1:10 or 1:8.

Will 243 Winchester work in an AR10?

Yes. It uses the 308 bolt face and fits AR10 (LR/SR) magazines. The CM10 243 ships with a Magpul PMAG 10 LR/SR.

Who makes a 243 AR10?

Chattahoochee Munitions manufactures the CM10 243 Winchester AR10 with a 20-inch barrel in a 1:8 or 1:10 twist, in Black Tungsten, Cobalt Kinetics Green and FDE Metallic Cerakote.

Who makes a 243 semi auto rifle?

Chattahoochee Munitions manufactures the CM10 243 Winchester semi auto rifle on its large-frame AR10 platform. Chattahoochee Munitions does not load 243 ammunition; Hornady, Federal, Remington and Winchester do.

What Is 243 Winchester? The 308-Based 6 mm Deer and Varmint Cartridge