I have a barrel chambered in .308 Win that I want to rechamber to .300 RUM. Will the larger reamer follow the existing chamber, or should I bore out to about .010 under the shoulder diameter of the RUM to the end of the existing chamber (until pilot engages bore)?

Through the headstock. It's running true to the existing chamber.

Thanks, Steve

I would bore it. Regards, Bill

Just like chambering a new barrel you have to remove so much steel.
If you don't have a roughing reamer, you will just make your RUM reamer duller quicker if you don't bore it out beforehand,

Thanks both.

quote:

Originally posted by dpcd:
Just like chambering a new barrel you have to remove so much steel.
If you don't have a roughing reamer, you will just make your RUM reamer duller quicker if you don't bore it out beforehand,

I personally wouldn't worry much about dulling a 300 RUM reamer. I have a once used from about 25 yrs ago. It can be borrowed or bought.

Of course you are right.

Yeah...That rifle....client is now in his 80's. Looking to sell Was disappointed to find the caliber was a hindrance to expected return