if you do a search on here, you'll find a post I made about running a 6mm reamer in a .243 chamber. It won't clean up, and it seems like it leaves a five to eight thousandth step all the way around. the location of your ring is just about right (about 1.80" from the case head). To fix this, your going to have to do a barrel set back of at least a quarter inch, and I'd go three eighths inch to get you a nice clean throat. The other solution is to find a 6mm Ackley reamer, and simply clean it up with a one thread setback (incase the head space is also off a bit).
You can do a quick check to see if there is a step in the chamber with a straitened out paper clip that has a small upwards bend on one end. Just rub it on the chamber wall. If there's a step, you'll feel it. Of course you could also see it with a bore scope, if you have access to one.
thanks everyone for the replies. i wonder if i could get it turned into a 240 weatherby or will it b easier to leave it 6mm
A 240 WBY mag has a smaller case diameter than the 6mm, so it's a no go. Plus it's not really any faster than a 6mm Ackley when it's all said and done. Of course you could also do the 6mm Rockchucker that uses a 28 degree shoulder. But the rest is very similar to the Ackley
If you decide to go with the Ackley, buy a .257AI bushing die, and a Forster .243 seater. Run the chamber reamer in the sleeve for the seater, and simply change the bushing on the sizing die.
6-06 ackley should clean it up, not?? If he's got the mag well for it anyway...
The real problem with the standard 6mm/06 and the 6/284 are that they are not any faster than a 6mm Ackley. The .284 case is shorter than the 6mm Remington case so that's also a no go. With the 6mm Ackley at least, there's an easy direction for reloading dies, and data is very common. Of course you could do a .30" inch barrel setback, and rechamber to 6/284. The next issue is barrel length! The Ackley, 6/284, and 6-06 all prefer a 26" barrel length.