September 2, 2007, 12:08 AM
The "tab" mentioned is only a fixture to hold the bolt in position when the barrel assembly is removed, since you don't want the bolt to get out of position when you need it located properly to engage the action slide during reassembly.
There are at least a couple of possibilities:
the mag. tube was not properly and fully inserted, so the bolt was practically hanging free of the action slide, and disengaged during firing.
The action bar has broken off the end of the arm that engages the bolt.
The bolt lock-up is damaged and finally allowed the bolt to blow open during the firing.
I have rebuilt guns that had been damaged in many more variety of ways than these.
I would rather not have had to fix ones that had been shot to death, but rather had caught them before the fateful moment of rigor mortis. Bringing one of these back from the grave is not economical, and these days, I would rather replace the receiver and refit the parts as necessary, except in the cases of engraved/inlaid and other special circumstances.
The better option for Model 12 shooters is them to have a Model 12 specialist give the mechanism a thorough exam at least every now and then, if you otherwise have a local gunsmith tend to minor repairs and cleaning.
The trigger assemblies are full of parts that need fitting of any replacement parts, and sometimes a used part substituted may seem to be OK (to the untrained eye) but not be proper or even possibly dangerous to the mechanism and/or property and people in the vicinity.
I have about 25 years experience since gunsmithing school as a shotgun specialist, with much emphasis on Model 12's and many other classics.
See my other posts here, at