In article 3fd333a7-0b99-4d89-8b66-c6fbe8199dd5
@n38g2000prl.googlegroups.com, says...
Some rifles have the bolt engaging lugs machined directly into the
barrel itself. I've been informed that some replace barrels in such a
system by cutting off the lugged section of the old barrel and
threading that onto a new one. Is it really that difficult to
directly machine lugs onto a new barrel and thus eliminate this
creation of a third part, a barrel extension AR 15 style? Can this
replication of the original barrel be done by a home machinist? What
process and tools would be involved, perhaps some internal grooving
and metal shaper work to cut the lugs or is it much more involved?
Any perspective on this would be appreciated. Thanks.


Easy. Just machine a groove the size of the locking lugs in the barrel
and then cut notches to clear the locking lugs when the bolt is opened.
But, the devil is in the details. How much clearance, exactly where are
the lugs when the bolt is open, how to get everything concentric and
aligned with the bore and so on. You will need chambering reamers and
head space gages. Except for machining the locking groove nearly
everything could be done by hand, if you wanted to; but it takes a lot
longer.

The reason they cut off the old barrel and thread it is money. Probably
a day, maximum, to make a new barrel that way versus, maybe, three days
to cut the locking lugs into a new barrel.

Years ago I built something similar, an interrupted thread locking
single shot action. Took me a while.

--
Cheers,

Bruce in Bangkok