I have an 11.5" barrel and a 5.5" FH that I want to attach for legal purposes. Obviously locktite is not enough, would silver solder do it? How to you go about this process? Is there any other way outside of a different barrel? Thanks

I have heard silver solder is AOK according to ATF.

The silver solder needs to start to flow/melt at 1150* to be legal.

www.silversupplies.com/catalog/metals/silver_solder/paste.shtml

#65 will work, and use kitchen vinegar on the threads (barrel and FS, using a Q-tip) to remove the parkerizing to get the needed bonding (just don't get the vinegar on anything else or you will need to reparkerize the bare metal spots).

P.S. it's going to take a Mapp torch or better to get the steel this hot to flow the silver wolder.  Using a porpane torch takes too long, and the heat will transfer way too much down the barrel during the longer process and cause problems (even with heat sink compound).

How do you know when it is hot enough? Does it need to be glowing? Where does one find a Mapp torch?

Quoted: How do you know when it is hot enough? Does it need to be glowing? Where does one find a Mapp torch?

You can get a MAPP torch at Home Depot

Heat the metal cintacting portion until it has a "Dull" red glow to flow/bond the silver solder.  If the barrel starts to glow bright red, you when too hot and this will cause some problems.

To test if you have the correct bond, let the parts cool and try to spin the FS back off.

I just had one of the welders at work MIG mine on.
I then cleaned up the weld with a Dremel and did the Hi-Temp Krylon thing.
Works perfect for a working gun.