Okay, so I've had an approved Form 1 for a Remington 870 (police trade-in) for almost 8 months now. It's got an 18" police barrel on it. I had previously expoxied a XS big dot onto the bead on a pedestal.

It's time to finish this project. I've got some hand tools and I'm not afraid to use them.

I'm going 14" on the barrel, and I'll chop the stock a touch as well. What's the easiest way to remove and reinstall the front sight? Will a MAPP torch soften the solder enough to get the base off? And will I destroy the tritium in the big dot? And finally, should I resolder, or just use Black Max Loctite for the reinstall?

No one?  Dremel and Sawzall?

Sorry, just saw this.

The Remington base is high temp brazed on and takes heating the barrel to a red heat to melt the braze.
That will destroy a night sight.
A Mapp torch should do it.

The epoxy on the bead will be a problem.  Likely the only way to get it off is with heat, but that will probably destroy the night sight.
You can try soaking the end of the barrel in lacquer thinner for days to dissolve the epoxy, but I suspect that won't work.
You're probably looking at a new bead.

To remount on the barrel, remove the finish from the area the base will fit and clean the old braze from the base.
Use 1100 degree silver braze from Brownell's along with the brazing flux to re-braze the base.
Clean up around the base to remove excess braze and solder residue.
Refinish the barrel and base than screw the bead back in.

"The epoxy on the bead will be a problem. Likely the only way to get it off is with heat ..."

MEK (especially gently warmed) eats epoxy.

Do not heat with a flame.  Hot water with MEK in a metal or glass container is more than enough.

Hey guys, thanks for the reply.

Mission is half complete.  The Big Dot came off with heat from the torch.  I slightly melted the plastic insert, but it's still working and glowing.  It even appears that I can reuse it.  

Just like you said, the solder melted when it got a dull red, and I pulled it off with a pair of vise grips.  I'm debating about cleaning the bottom of it and reinstalling it with Black Max Loctite instead of solder.  Should I just go with the solder?  I'd have to get another container of MAPP gas, when I took off the torch head, it started leaking.  I'd also rather not refinish the barrel, as I have no way to do so.  

I did the cut very carefully with a hacksaw and then dressed it with a file.  Looks pretty good, I'd love some recommendations about how to refinish the end though, I guess whatever product is equivalent to AlumaBlack, but for steel.

If the barrel is black Oxide or "blued"

Brownells Oxpho Blue

Should work for you, nice to have around for touch up work.

Or you can go to the local Wally World, Gander, Academy or such and buy the Birchwood Casey Cold Blue for about the same price minus shipping, but it doesn't seem to work quite as well.