Home Forums Hunting & Shooting Gunsmithing Pre'64 M70 barrel swapping

Do these line up closely as far as sights and stamping when swapped?..or are they a hit and miss proposition? Does one normaly have to take them back a turn and rechamber...I know all about headspacing so forget about lecturing on that part of the job.

What I'm contemplating is taking a 1947 270 barrel and putting it into a 1953 receiver in which someone has previously opened up the bolt face & extractor to a .532" belted mag.....it will also be rechambered to 270 Wtby.

99% screw on and line up just fine. Most headspace just fine too. Those two years should match up well. The trouble with having one go too far and setting back, is the forend screw boss will not fit the stock.

If you're going from 270 Win to 270 Roy, you won't need to set the barrel back for the rechambering work, 'cause the 270 Roy's finish reamer will totally remove the existing 270 chamber. But you will almost certainly need to set the barrel back whatever small amount is necessary to get the existing open sights and roll-stamps to line up, "time", in the right place, probably less then 0.10".

Jeff

No!, Not necesarily the case, the previous poster was correct, most of the time they will clock correctly, occasionally you need to set them back.

I've rebarreled several pre-'64 Winchester 70s with parts left from my Father's huge collection and never had a barrel line up with the open sights at TDC with proper headspace. All required shaving a little steel to get both proper sight alignment and proper headspace.

Jeff

Not only are the pre-64 Model 70's timed so that most will index perfectly, the Model 54 and the Model 70 are also the same!I have put model 70 barrels on model 54's and vice versa and they index perfectly as well. Only occasionally does a barrel turn in too far and then, only by a few degrees. GD

I have only done it once,but everything lined up perfectly and head space was ok. Remember,those rifles were massed produced and not chambered after the barrel was installed. Any barrel was screwed on, head space checked and proof tested.Then sent on it's way to be sold

If this is true it's pretty impressive considering the machinery of the day...there are 4 dimensions to hold in order to do this...

the depth from the receiver face to the locking lug abuttments
the distance from the rear of the lugs to the bolt face,..you have to make a couple measurements and calculate to get this dimension.
the length of the threaded portion of the barrel
the headspace as measured from the rear of the breech

if each were held to a tolerance of .001 tolerance stack up would have been a problem..these dimensions must have been held to .0005 or less to accomplish this.
..and the threads had to be timed very accurately on both receiver and barrel. Winchester must have had some very accurate jigs and fixtures to do this on manual machinery...but I'm sure they would have set the headspace and then cut the extractor slot and the sight dovetail and then positioned the front sight.

I sure would have liked to have seen thier setups for these machining operations....we have it pretty easy these days with CNC machinery.

The receiver and barrel threads almost look like they are hobbed, not cut single point.

This is not true. The pre 64 Winchester model 70 although made on an assembly line was final chambered and fit by hand with the bolt individually fit by hand and then electro pencil engraved with the rifle's serial number. Depending on the caliber and/or era, there were betyween 4 and 7 chamber reamers used. They used both finish reamers and burnish reamers earlier in the production for final headspace; after 1952 they eliminated the burnish reamer and recessed the bolt face for final headspace.

Individual rifles were initially test-fired and sighted in and later bore-sighted when technology advanced.

I rank pre 64 Win 70 in this order:

The best were 1948-1951. These were still finely crafted but had all of the changes to permit optics in place.

The finest made were the pre Wars, 1936-1947

Still pretty darn good but short cuts beginning were 1952-1958.

From 1959 the shortcuts just kept coming; later are ridiculous.