On Apr 8, 2:48*pm, Cydrome Leader wrote:
Steve W. wrote:
Cydrome Leader wrote:
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...%20with%20a%20....

RogerN

does anybody make plastic unfinished lowers, just for machining practice?

It would seem like a shame, and expensive to be using trashed lowers for
the next aluminum casting project.

As long as you follow the directions and have some ability they are not
real hard to machine. The biggest thing involved is to KNOW the machine
you will be using. If you know that your machine has .020 backlash on
the X axis repeatably then you can correct for it. If you think it does
but in reality it isn't repeatable then OOPS you get a scrap upper.

It's a chicken and egg sort of deal to anybody (like me) that's new to
machining, but familiar with what the finished product should be.

Do I right now have the ability to finish *a lower receiver? No, I do not.

Could I learn? sure, but it will take lots of practice, which at this
point would be futile and expensive if I bought a box of forgings and
jumped right in. I'm sure I'd learn quite a bit trying though, while
making a huge pile of scraps, but again, it costs to much to try.

You are not as far off as you think if you invest the time and you
continue to think and ask questions about why you are having problems
You have tremendous resources in this group: Lloyd Sponenburgh,
Precision Machinist, Bottlebob, and lots of others. Use them. The more
parts you make out of different materials, the better you will get.