Quote Originally Posted by sharpshooter View Post
There is a fix......probably controversial, but it seems to work because they do it all the time at the factory. This is a detail that probably no one knows about, nor has been considered a viable fix even to the back yard gunsmith. The factory barrel threads can be on the small side just from production tolerance, along with receiver threads a little big, or a combination of stacked tolerance. A few of us here know what can happen when the thread fit is sloppy......the barrel will end up drooping with gravity when cinched up. I found this out by chucking up the receiver and checking runout at the end of the barrel. You would be shocked how much droop a sloppy fit will create, and on the other hand, you would be amazed how straight and consistent a proper fit is.

When I toured the plant back in 2005, I got to "build " my own rifle there.(Like that was a big deal to me.....) Anyway...after I installed the barrel, we turned around to a fixture with V blocks and an indicator. I asked, "What's this do?" The gal replied, "We're gonna check it for straightness." She laid the receiver in the V blocks, and rotated it with an indicator contacting the barrel about an inch from the muzzle. A full rotation moved the indicator needle .001". She went on to state that if it was more than .020", the barrel is "adjusted" to be closer. To demonstrate, the next barreled action was checked and adjusted with an arbor press. At this point I was totally confused, as I just witnessed a worker straighten a barrel as it came off the profiling lathe. " You mean to tell me, that after that guy just massaged that barrel straight, you're gonna bend it so it's straight with the action? Isn't that counter productive?" About that time, the lead man for barrel dept. jumped in and clarified things. He said, "No.....were not gonna bend the barrel, we're going to "slip the joint".
The barreled action was moved to the straightening fixture with the arbor press. There is a V block placed under the rear bridge, and one placed 4 inches ahead of the recoil lug. After it is rotated to find the high spot, the arbor press is used to press right on the thread joint. What this does is push the joint laterally, despite the tension on the nut. This is done until the muzzle is fairly concentric to the receiver, mostly to insure that the barrel sets straight in the stock.
The tighter the thread joint, the less lateral movement is encountered. A class 3 fit will insure that the barrel will draw up and center itself very consistently. The trouble with that is, although it was called out as a class 3 fit, it was hard to hold on old machinery of the time, so they found a cheap and dirty fix.
I've pondered this, guess it could work in the event of sub-standard machining of the receiver face and barrel nut.
Thread fitment of barrel tenon to receiver is not critical- in fact, threads that are too tight are detrimental.

When I first started riflesmithing, I had conversations with those knowing far more than I to glean the "basics". Both "Daves" (Kiff, and Manson) agreed on this. The threads serve to bring the parts together- it's the critical shoulder surfaces (or the back side of the nut, on a nutted barrel) that bring the parts into correct alignment. These mating surfaces MUST be perfectly at 90 degrees to the centerline of the receiver. It's the clearance between the thread crests and roots of the parts that allows the shoulders to bring them into alignment.

If that is correctly done, any very minor "misalignment" due to thread tolerances will result in radial misalignment- which is virtually undetectable. The bore will still be in perfect axial alignment- meaning parallel to the centerline of the receiver, assuming of course that the barrel was correctly set-up when chambered. On a production rifle where the receiver face isn't trued, and the mating surface of the nut isn't perfectly square to the threads this "fix" could probably help.

Putting an action in an arbor press- with the pressure point inches ahead of the receiver face sounds like a sure way to tweak a receiver.