before i get berated as a bubba doing bubba things here...i just want to point out that i am aware in principle at least, that barrel extensions should as a general rule of thumb, be smoothbore as opposed to having any rifling, as there is no way to ensure the extension's lands and grooves line up perfectly with those of the existing barrel...

with that forewarning out of the way...could i chop off a section of a certain demilled barrel i have sharing the same caliber/bore size as with a barrel i do wish to use, JB weld the muzzle device on top of a flat shim and the flat shim to one of the chopped-off end of the cut demill barrel section, and, to avoid having to expand and tap the cut demill barrel section's other end, simply JB weld that end again, to say a thread protector, and expect to screw the thread protector over the intended barrel's threaded muzzle?

for what my barrel is worth, i dont see the need to spend almost half, if not more, of its cost on a smoothbore extension that matches neither in finish nor in desired length...if JB weld (or even say, Rocksett) would hold things together as laid out above, id be much more inclined to do that instead...


thoughts?

This sounds like a terrible idea and it took me half of your post to figure out you weren’t talking about the actual barrel extension, you are wanting to extend the barrel.

Edit: buy a barrel in the length you want.

Not sure that JB weld will be able to contain 40,000+ PSI if that is all that is holding it together.  

How long do you intend to extend the existing barrel?

Depending on the length you need, you'd be much better off with something like this:
https://www.midwayusa.com/product/1025140888?pid=160779

Out of curiosity, what is the desired effect?  Why re-use a de-milled barrel?

cuz i thought there was still some use to it...

at the end of the day, nvm this OP thread...turns out it was a bad idea, and the point has been taken...