Can a 243 winchester be rechambered to 6mm remington by reaming alone or does the barrel have to be set back too?

COL on 6mm rem appear to be about 2.8" what sort of COLs will SAAMI spec reamers give if seating to the lands with spitzer styly bullets eg nosler ballisitic tips etc.

1894,

You might run into a problem as the 243 Winchester is thicker just below the shoulder than the 6mm at the same distance if the barrel is not set back.

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saeed@ emirates.net.ae

www.accuratereloading.com

The barrel MUST be set back 5/8 of an inch. The diameter of the .243 at the shoulder is .454 & the diameter of the 6 mm at the shoulder is .429. On the 6mm case the .454 diameter is not reached till you are 5/8 of a inch back from the shoulder.
Generaly this can only be done on guns with heavy barrels where there is enough
steel forward of the chamber. I always just cut off the old barrel shank & start from there. New barrel threads are then cut. I do this because most barrel shanks are in the .600 to .700 (thousands of an inch) range anyway. (5/8 Inch =.625)

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[This message has been edited by Bear Claw (edited 11-08-2001).]

You won't see enough gain in velocity from 243 to 6mm to make it worthwile.I have owned at least 3 of each and a friend has owned a 6mm for 16 years.A better option is to rechamber to 243 Ackley Improved,6mm Ackley Improved or 6mm/284,all will clean up your 243 chamber without major barrel setback.

I redid a .243 and made a 6mm-.284 out of it and it is outstanding.

Hello BC

What is the diameter of the 6mm AI at that point ( don't have my cartridge book handy - still in storage from moving ).

Tom