According to ammoguide, the 375H&H can be rechambered to 375 H&H Flanged magnum, as every dimension of the flanged case is the same as or slightly larger than the belted case. The reason I am considering this is that I want to build this cartridge on a Farquharson action and the Ruger conversion would be a good trial run. I would like to know if someone has done this conversion and can share the experience. Besides the extractor on the Ruger,is there anything else that must be changed?

According to CIP chamber dimensions, the diameter of the flanged case is .518" just above the rim. This is smaller than the nominal .532" diameter of the belt of the rimless/belted case. So, the flanged case will not be supported for the .220" height of the belt recess and bulged cases are likely to result.
No. 1 ejectors are easy to modify. No other modifications needed, but the flanged reamer will NOT clean up the belt recess.

The #3 in 375 Win might work as a project. I've got one that has been chambered to 375 2.5" Flanged.

Of course, RA is right.
A #3 in that caliber would have heavy recoil. They only weigh like 6 pounds.
Now, I have rechamsbered several 375 H&H barrels to 375 FL.
Because of the belt area being larger, I cut off some, or all, of the shank and went from there. My favorite is a 91 Mosin with a Ruger #1 barrel on it.

quote:

Originally posted by dpcd:
Of course, RA is right.
A #3 in that caliber would have heavy recoil. They only weigh like 6 pounds.
Now, I have rechamsbered several 375 H&H barrels to 375 FL.
Because of the belt area being larger, I cut off some, or all, of the shank and went from there. My favorite is a 91 Mosin with a Ruger #1 barrel on it.

A Mosin is a very strong action. That would be one hell of a rifle. You're right about the #3 recoil. In fact the #1's have stout recoil in the bigger cartridges. MY bast friend is not recoil sensitive by no means and he got rid of a 458 mag right quick. Must be the stock dimensions, what do you think?

Funny you mention that; when I was at Ft Stewart in 1981 me and a friend both got #1s in 458; both of us had other large bores and thought those would be good.
Wow! I never had a rifle kick to much; and they have heavy barrels.
That was the only rifle I didn't like to shoot and I kept it exactly one month. Yes, stock is thin, and straight.
And those are not all that heavy either.
And I had owned a Ruger 45-70 since the 76 Centennial models, and I loaded it so hot that you could barely hold the forearm. Even that was manageable.
Now, the 375 is nothing in the recoil department. Like a 243. If I owned one, which I will never..