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Major Dave (retired) · January 9, 2013, 09:22 PM

The 243 Win was originally a .308 Win/7.62mm NATO (7.62X51 mm) brass case necked down to .243/.244.

The .244 Rem/6 mm Rem was originally a 7X57 mm Mauser brass case necked down to .243/.244

The difference is mostly in length, i.e. 51mm vs.57mm. OF course, the two different cases have different tapers to the body of the case.

So - NO, not interchangeable ammo, at all.

The only thing they have in common is the case head diameter, and the diameter of the neck (.243/.244).

Your dad's rifle, having its caliber stated as ".244 Rem" (stamped on the barrel at the factory) has a slow rate of twist in the rifling in the barrel, and will not stabilize the heavier bullet weights. The .243 Win has always had a faster rate of twist, which made it accurate with all bullet weights. Remington realized their mistake after a few years, and changed the rate of twist to the same as Winchester rifles, and re-named their rifles to "6 mm Remington".

Your dad's rifle, since it has a greater case capacity than a .243 Win, can be handloaded to about 100 fps higher muzzle velocity than a .243 Win, if you load the same bullet weight as the .243 Win.

January 9, 2013, 09:22 PM	#8
Major Dave (retired) Senior Member Join Date: March 12, 2008 Location: Between Dallas and Shreveport, LA Posts: 569	Different "Parent" cartridges - The 243 Win was originally a .308 Win/7.62mm NATO (7.62X51 mm) brass case necked down to .243/.244. The .244 Rem/6 mm Rem was originally a 7X57 mm Mauser brass case necked down to .243/.244 The difference is mostly in length, i.e. 51mm vs.57mm. OF course, the two different cases have different tapers to the body of the case. So - NO, not interchangeable ammo, at all. The only thing they have in common is the case head diameter, and the diameter of the neck (.243/.244). Your dad's rifle, having its caliber stated as ".244 Rem" (stamped on the barrel at the factory) has a slow rate of twist in the rifling in the barrel, and will not stabilize the heavier bullet weights. The .243 Win has always had a faster rate of twist, which made it accurate with all bullet weights. Remington realized their mistake after a few years, and changed the rate of twist to the same as Winchester rifles, and re-named their rifles to "6 mm Remington". Your dad's rifle, since it has a greater case capacity than a .243 Win, can be handloaded to about 100 fps higher muzzle velocity than a .243 Win, if you load the same bullet weight as the .243 Win. __________________ Artillery lends dignity to what would otherwise be but a vulgar brawl.