I recently acquired a pretty decent Pre 64 Pre War .270 WCF barrel that I would like to swap out with one of my throated and pitted .30 Gov't 06 Pre War Model 70s.

The date code matches the serial number- an added bonus.

My nearest gunsmith said he'd have to cut 1/4" to 1/2" off the chamber area to fit the barrel! Am I missing something here? I thought at most I'd lose a thread to get the sights to line up and the bolt to headspace...

Can anyone briefly outline the procedure???

I have done what you want to do a few times. I have never had to cut off 1/2 inch or so of a barrel to do this swap. The M70 indexes at the 6 o'clock position on the receiver. There is a corresponding index on the barrel. Simply take out the old barrel and screw the replacement on. If the index mark on the barrel is at the approximate 4 o'clock position, you can torque up the barrel to align with the index mark on the receiver. I use Brownell's moly barrel paste on the threads to insure against galling. Most Winchester barrels will align up nicely. If the barrel is at the 2 o'clock position or 3 o'clock position, you will have to take a little off (2 or 3 thousands). Or better yet, take a very light cut of the receiver face to make sure that the face of the receiver is square. This has to be done on a mandrel. Do not take off more than it takes to square the receiver. If the index marks still like a little to get to the 4 o'clock position then you take a little off the barrel where it contacts the front of the action. Remember, a little goes a long way. You can now put the action on the barrel while it is in the lathe and check it out as to where the index marks are. You will probably have to deepen the chamber a couple of thousands or so. All this has to be checked with headspace gauges. If you have to deepen the chamber a little, tighten the barrel to where it indexes with the receiver and then use a finish reamer, cutting oil and deepen it by hand. Again a little goes a long way, check your headspace often. There is only about 6 thousands between the go gauge and your bolt closing on the no-go gauge. Should the barrel initially line up on the index marks by hand or go past alignment, you will have to remove about 3/4 or a little less from the barrel until you get the index mark at the 4 o'clock position. You will have to deepen the chamber until your bolt will close on a go gauge and not close on the no-go gauge. It is really a pretty simple operation. Think this through, as metal removed cannot be put back. Go slowly, check your progress often and it will work perfectly. I sure don't think that you will have to cut off any of the barrel unless there is damage to the chamber, threads or the throat. If yo were going to do an Ackly Improved or something like that, you will have to cut off one thread to insure that you get the proper headspace when you re-chamber.

Oh, I forgot. If you have to take a thread off you will also have to take some metal from the cone of the breech end of the barrel. Be sure that when you align the index marks to check the bolt and make sure that it will close without any interference.