Is it possible to convert a .30 caliber Ruger No. 1 rifle from .308 or .30-06 to .300 H&H by simply reaming the chamber?

In theory the 308 might just clean up.

I would rather have a 308 or a 30/06 in particular if it's a 22" barrel.

The #1's are chambered in 300 Win Mag. Just buy one of these if you must have a mag. It's a much better cartridge than the .300 H&H.

True, but I want a .300 H&H, for the same reason people drive a 60's Corvette when a brand new one would drive better...

I understand. I have a 300 H&H also.

John Lewis is a smith in the Carolina's that seems to have some good ideas on #1's. If I was going to convert one I would have the hammer spring changed, the hammmer lightened and most of all the trigger improved.

Make sure that the 308 does not have an 1-12 twist.

One needs to check the chamber specs. The .308 is very large in the shoulder area and I know a 30-06 will not clean the chamber...I'm not sure about the 300 H&H but it does have a lot of slope...I personally would re-barrel it with a Lothar Walther 26" barrel...A 22" 300 H&H won't perform much better than a 30-06...

Hmm. Alot to think about, especially when I've already got a nice Model 70 in .30-06.

Let me add that if I had a single shot rechambered to .300 H&H that I would have it throated just a little bit longer. The throat in my M 70 seems so short.

If the rifle shot well as a 30/06 or 308 then it should shoot well as a 300 H&H. No need to pay for a new barrel.