We got the barreled action back this afternoon and ran some tests after taking it apart and inspecting everything.
There was a pair of clues for troubleshooting & throwing blame around early on, so an educating time for those on the thread: The runout behavior was seen on a different barrel from a different company. Chances of that happening and it being 2 screwed up barrels and not a screwed up mount are very low. Second clue: the barrel was stated to shoot 1 hole without the adapter kit installed, if the crown was so screwed up that threads were causing baffle strikes the issue would very likely cause accuracy problems as well.
One note:
@GBMaryland the front action screw on your chassis is impinging on the barrel tenon, the screw is about 1 thread too long. See below, there's a nasty ding in the corner of the barrel tenon where the action screw is driving into it.
Testing on Bench : I first put the barrel on the optical comparator to show the shoulder on the shadowgraph in 20x zoom, it lines up true on the comparator grid. There's a different in the chamfer from one side to the other on the barrel. This is not due to eccentricity in the threads or shoulder WRT to the bore. Instead it's because the OD of the contour had a lousy relationship to the ID of the bore. My program cuts a chamfer all in one setup and sometimes if the OD/ID is poor then the chamfer looks out of whack. Additionally the muzzle cap is a shelf item, we make them in large batches of different OD's and screw them onto the barrel when it's done. Someone previously opined that it was likely made at the same time so it would have a clean fit. That's not the case, they're not created at the same time. If the shoulder was crooked the thread cap would show a gap between the shoulder and the cap just like if there was a gap between the TBAC mount and the shoulder in the picture posted originally. There is no light gap there. It's pretty darn hard to get a barrel 26" long onto a 12" wide comparator table but we got pretty close.
See the photo below:
Testing in the spindle.
I ran the same test of mounts and adapters in 4 different ways to rule out potential problems.
Combo 1: bar stock drop from the scrap bin, threaded 5/8-24
Combo 2: Existing barrel, dialed in on the bore to within 0.0002
Combo 3: Set the shoulder back 0.005"
Combo 4: Set the barrel thread back and cut completely new threads onto the barrel.
We also put the barrel into the contouring lathe and skimmed out the OD/ID relationship to be much closer since I was bugged by it being off (it wasn't our contour, customer supplied blank).
Mount A: TBAC CB mount from our stock, new and unfired.
Mount B: 419 system consisting of a universal adapter and the suppressor mount.
The 419 base adapter that screws onto the muzzle was confirmed on the barrel and the test stub to be free of runout. This is the piece that the TBAC adapter mounts onto it.
Test 1: Check each shoulder for runout
Test 2: Snug TBAC CB mount into place and check runout on the taper.
Test 3: Snug Area419 adapter (the part that touches the barrel) into place and check runout on shoulder and taper
Test 4: Snug Area419 mount (the part that touches the suppressor) into place and check runout on the taper where it contacts the suppressor.
So there's a bunch of fiddling and testing that went on, it took about 90 minutes to get through all the stuff and take short video clips. Unfortunately I don't know how to pause a video on an iPhone and string together a stack of clips.
The material slug is there as a reference standard for all other tests. If the test and indicators are repeatable then the runout from each iteration should be the same between the barrel and the slug if the barrel isn't the problem.
Theoretically if there is absolutely no runout in the machine and the test parts then there should be no runout discernible under testing the material slug with all combos of the mounts.
TBAC mount on the Combo 1: material slug ~0.001"
TBAC mount on Combo 2: "as returned" barrel ~0.001-0.0012"
TBAC mount on Combo 3: barrel with 0.005" skim shoulder ~0.001
TBAC mount on Combo 4: freshly setback barrel ~0.001"
Conclusion here: TBAC mount showed about 1 thou of runout through all tests, the only change being the Combo 2 test which was slightly more. This is the test where dialing in the barrel again could easily have created the slight increase in runout detected.
419 universal adapter: no appreciable runout detected on any of the test combo's. No further discussion needed.
Next 419 TBAC mount system assembly. The used mount had a discernable contact ring on the taper from the suppressor contacting it during use. This contact ring shows to be inconsistent around the circumference indicating inconsistent contact on the taper.
We used the contact mark on the taper to indicate from since this is clearly where the customer's suppressor was touching the mount.
Combo 1: 0.004-0.0045"
Combo 2: ~0.005"
Combo 3: ~0.0045-0.005"
Combo 4: ~0.0045" (Video Below)
Projecting that runout over the length of a 9" long suppressor would result in the videos that
@Westbound created, excessive TIR at the endcap aperture.
The test was repeated for the second 419 mount that was supplied by the customer in the box.
Combo 1: 0.0055"
Since this component was unused by the customer and it showed the same level of TIR on Combo 1 testing I stopped at that point. We had localized the culprit and I needed to get back to other work.
I have not had a chance to upload the all videos because they're on my phone,.They look like the ones from Randy except they're in a different lathe. This is the last video after having tested all the various combinations. This is Area419 with the universal adapter and the TBAC mount on a freshly cut muzzle.
Everything is going back to
@GBMaryland tomorrow.