Gentlemen, a question. Assume I have a nice m70 in 30-06. If I had a new mag box, follower, spring and did some work on the ejector, could this action, with some additional work on the rails, opening and new extractor make the move to a .375 H&H????

I must be missing something, or is the cost simply too excessive? Inquiring minds need to know! Thanks, Arthur

Arthur, you just gave the recipe for all the original pre-64s chambered in 300 H&H and 375 H&H. Pre-64s were always a on-size fits all proposition; the only difference between factory built rifles in 375 H&H and a 250/3000 are just the changes you outlined.

I wish Tom Burgess would input...If I remember from his class in Susanville years ago the 300/375 were heat treated differently and he wasn't too keen on simply opening up a standard action....Keep in mind that I haven't looked up my notes, since they are buried in my "system"

Forrest and Mr. Wiebe, thanks for the input. I knew that they were the same length and that some modifications might be necessary. I had also heard about the differences in heat treating--as I remember it, if you look closely at both actions side-by-side you can see the change in coloration on the H&H versions...Perhaps Mr. Burgess will add the expertise here??? Otherwise a $600 action can become a $1200 action fairly easily!

Again, thank you for the input and to both of you, many thanks and great appreciation for the chance to hold and admire the raffle rifle. Both of you are owed much! (I told you, Forrest, that I would not win!) Arthur Olds

Two of the most knowledgeable m70 guys around,Echols& Miller,IIRC, believe the newer classic m70, is a better choice for 375hh.
I find pre64m70 300hh&375hh rifles can have compromised load length issues with some bullets, p64 are a shorter receiver than the newer classicM70..and looking inside the old p64 H&H action, theres already enough metal removed from the feed ramp to make me not want to remove anymore.
Theres good reason why some manufacturers decide to make true magnum length receivers.

If your not nostalgic, howbout maybe a 375ruger chamber instead???

I prefer to use the newer Model-70 for the 375 length calibers however if the a Pre-64 is the action of choice I will find an action chambered for 30/06 or 270 rather than a factory std magnum or long magnum. By doing so allows me complete control over the dimensions when altering the bolt face and allows me to obtain a longer (appox. +.070) bullet ramp without the razor edge at the top of the ramp and gives you a much thicker lower recoil lug seat. I do not "go the the rear, Hmmm ?) any more than to clean up the back wall of the action just ahead of the middle guard screw but do control the over all I.D. of the new mag well opening. I do not install a new magazine box that is longer than 3.600 for an I.D. OAL. The longer ramp also allows a shallower feed ramp angle which helps eliminates some feeding issues. When machining the underside of the feed rails I have more metal to work with on a 30/06 action than on the factory magnums. The top and side loading gate can now be opened up for ease in loading but you'll have to install custom scope bases when you open up the top side as the original rear scope base screw pattern is now missing a partner.

Rockwell hardness test on many, many dozens of actions post war, pre-war, Std and Mag length has convinced me that some Model-70 actions are just way to hard and I have had these actions drawn back before starting any major metalwork with no ill effect.

Any of the technique's mentioned above should not be attempted by an amateur hobbyist and only by the hands of a competent professional. This conversion is not as simple as the web makes it appear.