I just spent hours reading and searching this site the interweb for info on finishing my lower. This is my first attempt and I found a ton of great threads with info.
I plan on machining mine on my Bridgeport mill without a jig using blue prints. What I couldn't find was a list of suggested / required end mills to purchase for this. ie: dia, flutes, loc, oal, etc.
Most of the tooling kits I found were for router and drill press use.
Another question: is it better to drill and ream the holes through the lower or is just drilling them accurate enough?
Thanks!

Download this, print out a copy, and you have your bible.   All questions you have, are answered within.

http://arlower.ray-vin.com/ar15/ray%20brandens%20complete%20ar%2015%20build.pdf

Reaming is more accurate with better dia.  However by default, this means additional operations.  In manufacturing, reaming is not necessary with a tight Bridgeport and good fixtures or work holding.  Also use Fluids & Coolants (https://www.mscdirect.com/browse/tn/Lubricants-Coolants-Fluids/Metalworking-Fluids-Coolants-Equipment/Metalworking-Fluids-Coolants?navid=12107400) in this operation.

Have fun.

This is my thread on milling an 80% on a mill.  I'm not sure how much longer I can claim "I am not a machinist" but I still have no formal training, so take my suggestions and info for what it's worth.  There's a ton of info in that thread, most geared toward the new guy as I had to learn it all by trial and many many errors.  I just put all of my experiences and knowledge together in hopes of saving others some of the pains I worked through.  FWIW, I've done and walked others through something in the neighborhood of 50, everyone of them was functional.

Cliff's notes, a 7/16 end mill will give you the proper radius.  I run the same tool path with a 3/8 roughing end mill to hog out the majority and still leave a safe buffer for the accidental over run.  As other have stated reaming is much more accurate than drilling alone, but I've found cutting the safety and FCG pin holes with carbide end mills yields excellent results.

Yes, it's a great resource.
It also has prints for the machining jig/ fixtures.

I learned of this too late, as I had already bought a jig, just to have good holding fixture.
As shown in my Grizzly mill/drill.

Thanks for all the info guys.
Mirror - I don't know how I missed the ray-vin link, that's great.
CPT- the drill/ream deal is a throw back to my TD&G days, we did a lot of close tolerance work.
AFC - yours was one of the first threads I saved a link to.

I'll be sure to post some pics when I get it finished.

I used Ray's video and documentation when I milled a 0% raw forging.   Lots of good info in there.  Far beyond what's required for an 80%, but lots if good info.

Yes. Drill and team the holes. Before mulling the pocket.

7/16 long 2 flute endmill for the pocket.
Long 1/4 endmill for the trigger to go through.

Or you get lazy and use a 7/16 Drill on the 4 corners and use a different sized endmill to hog out the rest.

Indicate off the front pivot hole.

Much easier throwing it in the cnc tho. Lol

Thanks! I wish I had a CNC. Closest I get is my Bridgeport with the DROs I installed on it.

Just realize I my spelling errors there lol.

At least you have the read outs though. Its a easy bridgeport job for sure.

So how'd it turn out?

Only until it isn't, then it is very bad....

Reaming only requires replacing the drill bit with a reamer and changing the speed... if you bother doing it, do it right.

Center drill, drill, then ream, then move to the next position and lock the table.  Time-wise it is really no different.

You act like you want your holes in the right spot!

Somewhere well north of 50 now.  No issues with any of them.  Agreed, one could spend a little more time, and do what you said, which is the correct way.  I haven't found a reason to "yet".  They end up much much better than holes drilled using a standard twist drill through a jig and we all know 1000's upon 1000's are drilled that way and work just fine.