RogerN wrote:

"Pete C." wrote in message ...

RogerN wrote:

I'm close to milling my AR lower receiver, this "95%" machined receiver
needs a pocket for the fire control group and 3 holes cross drilled for 2
pins and a selector/safety.

I found some instructions for machining the pocket using a DRO, they
recommend drilling the selector switch hole, machining the pocket then
drilling the trigger & hammer pin holes. Why not drill all 3 cross holes
in
that 1 setup and then machining the pocket? I would think the drill bits
might be more likely to walk as they start through the 2nd side. I don't
see a benefit to set up for drilling, turn turn the part for milling,
then
turn back to the first setup to drill 2 more holes, any idea why they
would
do, or recommend this?

https://colfaxtactical.com/docs/Fire...%20a%20DRO.pdf

RogerN

I drill all the holes in one setup long before milling the FCG cavity. I
suppose one theory for drilling after the FCG cavity would be to reduce
the chances of the drill getting off course, but that doesn't seem to be
an issue in my experience. The Ray-Vin guide is the best reference IMO.

That's more what I was thinking, drill the cross holes first in one setup
and then mill the fire control group. I have the Ray-Vin guide and a blank
lower also, the "95%" machined lower should get me shooting right away and
the 0% won't be rushed.


Do you know how long it takes to completely machine
a lower using the Ray-Vin guide?

Nope, but close. I use the 30% lowers from TM, so that saves the magwell
and decking steps. The 30s take most of a day to machine on a manual
mill working at a careful pace with lunch and dinner breaks. A good
chunk of the time is the 8 or so setups and getting each one indicated
and edge located.