I have a Winchester M70 action.
Previously set up in .375 H&H with
The .532" bolt face.

I would like to have the action made into a .35 Newton.

The Newton rim is .525" from what I have read.

Is the existing bolt face unusable for the Newton?

Or should I go with an '06 bolt faced action and have it opened.

Thanks....

Howell's book "Forming Wildcat Cartridges" lists the 35 Newton as having a .528" rim, and since you will probably have to re-form cases from 375 Ruger brass which has a .532" rim I would just use the existing bolt.

Thankyou for the reply.

Yes, I will most likely use reformed Ruger cases.
But, if I do get proper head stamped cases, will they work properly.

That's what I'm worried about.

Will the magnum bolt face be too large to work properly.

That's only a total difference of .004", .002" per side so as long as the extractor is still getting a good bite on the cartridge rim you shouldn't have any problems due to the cases being a little small; the chamber is going to hold the case centered on the bolt until things are loose enough that a few thousandths won't matter at all.

CC,

Yesterday, while looking for something else (as usual), I ran across a group email string initiated by Lawrence Wales (author of two books that I own regarding Chas Newton) - poling a group of 1916 (Model 1) and 1924 (Model 2) Newton manufactured rifles. The question posed was the factory bolt face relief machined for the 30/35 Newton cartridges. The responses ranged from 0.538" (very early M1 runs) to 0.532" (very late M2 runs) with 0.534" being both the average and the majority of the measurements.

Regardless your M70 boltface would be just fine for correctly dimensioned brass.

Regarding properly dimensioned brass, there is a company in Florida selling Newton head stamped brass which you do not want to use as it was spec'd from the later runs of undersized Western mfg's brass. Captech International lists 30/35 Newton Jamison' brass that I understand is correctly spec'd.

A word of warning, be sure that the reamer specifications that you'll be using match the reloading dies specifications that you'll be using.