Originally Posted By: Texas SwiftyGLShooter, another article I read confuses me more. It said the barrel extension is what's head spaced therefore no need to check. Is this correct? I'll never learn without asking. I've read many of your posts & you are very educated, thanks. You're the man!
JD
OK, this might get confusing. They first turn the barrel. thread it for the extension to be hand tight, pull the extension, rough ream the camber, check for HS with extension screwed on by hand then finish reaming once they are close with the rough cut chamber checking as they go.. BE is then torqued to about 140 Ft. Lbs and the port drilled.
Here is a great well written description on barrel making for the AR.
http://firearmsdesigner.com/?p=153
If the chamber was reamed too deep and the extension is placed you will have excessive HS. Only correctable by pulling the extension and cutting the back of the barrel off and redoing the chamber/BE as above. The issue is by now the gas port has been drilled so you would have to hit the distance exactly one turn in, or increments there of and as you do this the gas tube protrusion increases. You can usually get one turn safely and if need be shop for that tube that is just a tad shorter. The chamber that is too shallow will just require installation of the reamer for a deeper cut. The issue here is that not all reamers are the same stamped whatever. Throats, necks, shoulders and bodies can all have various tolerances and you may have issues even with that.
The process of fixing one often times would exceed the cost of a new barrel from some smiths so if a guy gets a bad one based on measurements then he should look to the manufacturer. Now it is possible to stack tolerances in your favor.If you were say over 0.002 or so you might well be able to fit a different bolt with a slight bolt depth variation and cheat the culprit.
"Fitted" bolts are done by chambering a barrel and going through a box full by hand looking for that one that is just tight enough to make the chamber dad nuts. I ahve read several "custom" makers take this approach. They don't grab a bolt and start fitting from square one. No time for that and making money. They have their accepted HS gauge set up bolt, looks like a long bolt with no extractor/ejectors cuts and a long tail they use to set the reaming depth on the barrels. Checked when finish reamed and they are GTG. Now the extra $$'s you spent for "fitted" comes into play and trust me fitted just covers a range of + or - a few thousandths. Not worth the money IMHO. Once you have brass fired in your chamber you now have fitted brass just like you would regardless of the tolerances of that bolt that cost you an extra $30.00 A bolt face may vary, on the 223/5.56, from 0.120 to 0.127, in depth. Lots of elbow room.
Based on the quality of CNC machining and chambering we are seeing less and less over sized chambers. I might point out that we ROUTINELY blow out shoulders on cases as much as 0.015 and have no issues.
If I were buying your rig would bet my lunch and my personal body parts that shooting a barrel from WOA will be fine. The manufacturing process of these barrels requires at least two or three checks and the QC final out the door should pick up overly deep chambers.
Greg
