Here's a few gunsmithing Tips.  You will not see these tips on the Bushmaster DVD or Video Tape.  However, these tips will keep your AR15 from getting inadvertant stratches and mars to the finish of the lower receiver.  First, tape the two sides of the receiver when you install the Bolt Hold Open Latch.  Scotch tape is slippery and works quite well.  Use a BRASS PUNCH to hold the Bolt Hold Open  Latch in place when you attempt to drive the Bolt Hold Open Latch Pin into place.  Use a BRASS OVERSIZED PUNCH to seat the pin.  The finish will remain in place and your pins will look more professional.  I also used a BRASS HAMMER to drive the Trigger Gaurd Retaining Pin into the lower.  When done, remove the tape from the receiver.  The Scotch Tape and Brass tools will keep your receiver scratch free.  Also, take as much time as you need to assemble these AR15 lowers.  More effort and time assembling will translate into better quality.  CARRIERKEY

bodyshop masking tape the whole lower and go to town on it.

I use the blue painter's tape, as it doesn't leave a sticky residue. As for tools for the bolt catch, I just use a Dasco 5 1/2" X 3/32" pin punch and 6-ounce tack hammer.

Those tips have been around forever, but it nice to see them brought up once in awhile for guys who have never done a build.