I've never purchased nor have I heard of JB Weld before yesterday
Wow, and people say I live under a rock!
J.B. Weld is the most famous and common and readily available of all epoxies.
I generally avoid epoxy like the plague. It is the gunsmith's crutch. However, on very rare occasions, I do have to make use of the crutch. But I still don't like epoxies. I have NEVER had real success with hardly any of them. Acraglas is the worst. (ok, Micro-Bed was the worst, since 75% of the time it wouldn't set up and remained tacky... but it's not made anymore. No great loss there.) None of them really stick to wood very well, with the much-vaunted Acraglas being very brittle and simply flaking itself off of the wood. Personally, I don't care how many people sing its praises, as far as I'm concerned, it's worse than $#@*. The ONLY epoxy I have tried that I have found I can rely on at all is plain old J.B. Weld. No, it still doesn't hold wood nearly as well as my favored Titebond glue, but it does OK in no-stress applications. It will, however, stick to steel like nobody's business.
If I do manage to need to do something like fill some unusual area where fitting in a new piece of wood and glueing it in place would be an awful lot of trouble (a problem caused by me screwing up!), I reach for the J.B. Weld. I would not consider any other epoxy at this point. I can even mix in black pigment to make the epoxy a sooty black instead of the obvious gray plastic appearance.
I would not consider J.B. Welding a barrel tenon on a working gun (I did once J.B. a peeled-off underrib on an old gun just to make it more presentable. Cleaning that whole thing off and soldering it on would have been a lot more work than it was worth). The heat from firing would probably eventually soften the epoxy enough to break it loose.