I am looking at processes to accurize the AR15 platform in the same manner gunsmiths accurize bolt actions. I am looking for insight into machining and truing the actions rather than the usual "buy a quality barrel and trigger" statements.
Any input will help!

Thanks,
usmc5593

Considering the majority of parts are already machined to tight tolerances, there isn't a whole lot you can do. And that is a good thing. If you have a quality barrel free floated and have a good trigger (or just mind your trigger control) you are already 9/10 the way there. Some folks will recommend bedding the barrel extension into the upper receiver and bedding the gas block onto the barrel, and that is a reasonable thing to do if you are chasing extremely tight groups, but if you can get .5-.75moa out of a match barrel without doing it, you will only gain so much.

The thing about the AR platform is that it is the ultimate "lego" system. What you get in is a direct relation to what you put in. Stick a nice Satern or Lothar Walther barrel on a gun and you can get .5" groups, take that same gun and stick a $100 Sportsman guide barrel on it and you will get 2"-3" groups.

Pretty much sums it up.

if your barrel isnt chrome lined you could try fire lapping.

Free float the barrel.  Lap the upper ( has mixed reviews ).  Quality repeatable sights.  Fire lapping.
That's about it with the limitations imposed

has anyone tried to lap the upper?

what about bedding the barrel extension

Or not. Any reasonably well made barrel will not benefit from having sand shot through it.



 

I've lapped an upper, but I don't have any before/after data to show it was an improvement.



It definitely wasn't square to begin with.



 

You should ask this question in the variants forum. The main guy I hear recommending this procedure is Bill Alexander of Alexander Arms. Actually, you should call Alexander Arms (make up something about doing the research before building a Grendel and you want to know what is involved with bedding a receiver/barrel extension and why it is that he recommends it).

When I spoke to my gunsmith about it, he said he could definitely see where it would help, but the guy is a benchrest shooter (made one sick ass 6mm Dascher BR rifle that is absolutely insane) and is one to do every little bit to chase accuracy where if I get a 3/4" group with an AR, I pack it in and call it a good day. Basically, it would remove any trace of play between an upper and barrel. Lapping the receiver for the barrel before doing it would be even better.

how do you bed a barrel extension can some one explain this or even show pics of how to????

Most use something like red locktite on the outside of the barrel extension before inserting it into the upper receiver.  This would fill any voids and solidify the barrel to the upper receiver.  I talked to someone(John?) @ WOA and they recommended this along with torqueing the barrel nut to nearly 70ft lbs, on top of lapping the receiver face.  I lapped the receiver face and put a lot of torque on the barrel nut but I neglected to bed my barrel right off the bat...if when I take my rifle out and find out the barrel is a shooter I may go back and disassemble my upper and then bed the barrel.

what is WOA???   let us know how yours turns out...  i am about to build a rifle soon got most of the stuff here and the rest on order...  what about lapping the bore??? does this help accuracy...  or should you do a shoot and clean break in???

sorry not trying to steal this thread but im also very interested in "accurizing an ar"  so this is what i am thinking of doing to my next build

- lapp the upper reciever
-  Hand Lapp the barrel with Break Free Bore Past with a little clp/Bore past and a Mop swab with Proshot coated rod and bore guid... about 100 - 200 slow and steady
  strokes final polish with Flitz polish...  and then a shoot and clean using remingtons 40X with bronze brush and 40x with patch and Jag...  for about first 10 shots
-  Free float tube/rail
-  Good trigger job
-  Titanuim Firing pin??
-  Chop the hammer to make it low mass hammer??
-  Chrome Bolt Carrier Group (Polished)
-  Take off muzzle break and have crown cut to target crown and put muzzle break back on ???
-  Bed the barrel extension with red lock tite and tork down to around 70#

Is there anything else...  any little thing that i could do....  or is any of the steps above not good???
im not trying to get a bench rifle here but i dont mind doing the extra steps from the get go... on a new build, to get a better shooter...
is there anything else one could do???  

White Oak Armament

Relevant thread

This is the only way I was able to get one of my Colt 6724's to be the real shooter I knew it could be.  NOTHING else worked!  The receiver was on the loose side and the barrel extension on the minimal side...

 

Here is a "Bubba" fix for the sloppy receiver fit and it works quite well for a long time––- we place the breech of the barrel down on a table and spray paint about the first 3inches with engine paint or Brownell's Teflon-moly and bake it for a bit.  When you force it down into the receiver it will now be a very tight fit.   I have a Bushmaster 16 inche A-1 barrel that I am afraid to reveal how well it shoots––-
Mikie–– within a spit of the Gulf..

Don't even think about it.