Details
Confusion verily abounds.
I will try to assemble the pertinent points that some have caught, and some left unsaid.
The spare barrel shown is a solid frame barrel, but the shotgun in question is a takedown version.
The Model 12 had no solid frame version until decades later, a simplified and less dressy appearing version called the Model 25.
That barrel could not be for a standard Model 12 or a takedown model 97.
The appearance of the solid frame threads is a good bit coarser pitch than the threads of a disassembled takedown barrel without the barrel extension, but has the same thread pitch (but not diameter) as the external threads of the adjusting sleeve used on the takedown, but with dissimilar features.
Notice that the gun pictured has a magazine takedown pin and magazine band; both are hallmarks of a takedown version. The solid frame has a plug end in the magazine tube that enters a hole in the barrel band that does not surround the tube - just the barrel, and naturally is also absent the barrel extension.
There is a magazine retaining screw only on the solid frame version M-97, so any screw in that general area on the takedown version would be either the chamber ring retaining screw (about 3/32" dia.) by the ejection port or the takedown adjusting sleeve lock screw (about 1/8" dia. headless) in the side of the barrel extension.
That's the screw noted by R-McM in post #15 and 17, but as figured out, is not a mag. tube retaining screw.
The stock round knob configuration was a common style on early 97's, along with the metal buttplate in Neidner configuration. That was one of the stocks I carved in gunsmithing school.
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"The proper sequence is to rack the slide back. (Takedown) push mag pin through to the other side, rotate mag tube 1/4 turn, mag should come out partially. Rack the slide to locked position firmly and the mag tube, fore end with action bar attached should come out of the receiver."
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There really is no need to open the bolt on a Model 97 or Model 12 during takedown procedures, and there should be no need to slam the forend/bolt closed after opening to get a magazine tube to slide forward. Why use the slide as a slide hammer? I've only seen that done by a clown masquerading as a gunsmith to prove an improperly assembled 97 that he had reblued could come apart without tools. The goof had improperly assembled the magazine tube components. I had to demonstrate in front of him that the assembly was wrong, and after rework of the assembly, the magazine tube freely slid out with two fingers. Taught an old horse a new trick that day.
By the way, no need to mention both the magazine locking screw (for the solid frame) and the interrupted threads of the takedown magazine tube in procedures, since the gun couldn't have both features. Also, the interrupted threads typically will not disengage in either direction, since usually the helix of the thread binds before passing the interrupted cut in the threads in the frame. In other words, expect that tubes only "back out"- and don't usually "front out".
The magazine plug/barrel guide also inhibits rotation beyond the inbuilt stop limits when assembled.
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Here are your most likely answers.
The magazine tube plug (end cap) is improperly assembled and won't allow sufficient rotation to disengage the interrupted threads from the frame
The tube threads have been severely deformed or the edge of the barrel extension interferes with the withdrawal due to raised burrs or deformity
Some or all of the above
Kirby
[email protected]
Winchester Specialist gunsmith