Originally Posted by mathman
Quote
The barrels were broached(cut),stress free and very accurate.


Usually when it is said rifling is broached that means the grooves were all cut in one pass with a gang broach like this:
[Linked Image]




When it is said rifling is cut we're usually talking about the machining being done one groove at a time, and with many lighter passes of a hook cutter like this:
[Linked Image]




Of course, they are both cutting mechanisms. Which did Winchester use?




"Starting with the general shape from the drop forginging, the outside diameter wa staightened by hand with 15 pound hammers on anvils.

From this step,they were mounted on a lathe,their high spots chalked and turned to round.

Next the barrels were deep hole drilled from chamber end to muzzle.....

Following drilling,they underwent anothet straightening procedure with control intended for the inside diameter.For this process, ther were several turning,grinding and straightening operations which usually guaranteed concentricity.

With this established,the bore diameter was next reamed.

Rifling was performed after reaming. Each groove was cut individually by the "hook" method whereby a rifling head with a single cutter blade was pulled from muzzle to butt.The head was so spring loaded that itwould make gradual cuttings,removing fine chips from each groove........

After rifling the bores were lapped. A steel rod with the appropriate twist at one end was inserted in the bore and cadmium lead was poured around it.....an operator then pulled the rod back and forth,lubricating the bore with carborundum oil. This technique removed burrs and left a glasslike finish in the bore.

Once finished to this state the barrels were inspected......

Barrels which survived inspection were then belt polished in the barrel polishing shop.....

After this they were chambered. This took three to seven tools depending on the caliber....when thechambers were complete,they were still sightly undersized to allow for final headspacing....

In 1955 the hook rifling system was supplemented with the "broach rifling" process.The former method was retained for the target styles, the Custom Shop and the Model Shop. The new operation was was applied to the remaining production styles. The advantage of broach rifling was time savings as all grooves were were cut with a "one pull" operation........

"The Rifleman's Rifle"...Rule;pgs 53 and 54.

I left out a lot of steps in polishing and finish and stamping.This was the barrels....we won't even discuss the receivers and final assembly.....

Those who know WTF they are talking about,who have actually shot rifles made before and after 1955( instead of speculating and guessing about it) will know that the barrels made by both methods are easily MOA or sub MOA barrels..I know this because I have shot many examples of both in a variety of calibers.

The hand lapping that the later barrels did not get was accomplished by about 100-200 rounds of use.

I took a 1963 270 recently that had been shot little, if at all...first trip to the range and it shot sub MOA to 300 yards.It will hang with any M70 made by anyone, including FN

I suspect that any pre 64 M70 barrel made by either method saw more TLC tha any 1000 barrels built by anyone else.

Swampy go get some and actually shoot them......quit posting BS. It's unbecoming.....



The 280 Remington is overbore.

The 7 Rem Mag is over bore.