Solder it, they say

[Clark Badgett]

One problem with using solder is that the two surfaces MUST be flat and clean to each other . If not the solder will not form a strong bond with the two surfaces. Too much heat and you "fry" the flux and you HAVE to start over- period . Thick epoxy will flow into all the nooks and crannies of the two surfaces and give a good bond. If you want to extra secure then drill & tap for a 6-32 or 8-32 screw into the hook of the breach plug and thread it but don't go crazy with the depth of your tapped hole.

I think you may have pointed out what is happening. JB it is going to be.

[David R. Pennington]

Clean means shiny bright metal made that way with file or abrasive. There is no such thing as spot soldering. A spot of solder would not hold anything. Too much flux is likely worse than none. Think thin film of flux. It's only purpose is to keep oxidation off the surfaces while being heated and any excess must be evaporated before any bonding can happen. The heat needs to be indirect, burnt flux turns to carbon and nothing will stick to it. Tinning is a good idea. Shake off the extra solder after tinning. I like liquid flux for this type of soldering. It takes a little practice. You do need flux designed for soft soldering, not for brazing. 50 / 50 is easier to use than lead free. Heat heavier areas first. Don't overheat. If you overheat walk away. Come back later and sand back to shiny bright metal and start over. Once you get the hang of it you won't believe how easy it is.

[kutter]

Most any lead/tin soft solder (50-50,,60/40,,70/30) or one of the greenie Silver soft solders (tin/silver) will do. I use these and common  paste flux (No-Corrode) sold in the plumbing/solder section of the DIY store with any of them and they all work fine.

I do any common soft solder gun repair needed including re-lay ribs on SxS shotguns and double rifles.

I stay away from so called 'acid flux' (Zinc chloride) becasue of it's nasty after rust tendencys. It does work great, but if used in a restricted space like betw ribs, ect and not completely washed out, it will come back as a nasty coarse after rust that is nearly impossible to get under control.

Nothing special or proprietary about the solder or paste flux.
If there is any trick to it's use, it's the same old things about a clean surface, close fitting joints and surfaces.
Tin the surfaces before joining, Flux the surfaces again before clamping. Apply heat till the solder melts but not directly to the joint as it'll burn the flux away and the solder won't adhere to the base metal.
Keep things clean!
Don't over heat,,only enough heat for enough time to melt and allow the solder to flow into the joint. Add a touch extra solder if needed.
A close fitting joint shouldn't necessarily need any and soft solder is not a strong gap filler.
Let it cool naturally when done,,don't pour water on it to cool it off.

[RL]

Although I'm not the OP just want to thank everybody for the solder lessons. I managed to attach two ramrod pipes last night. Once I realized you can't run a bead with solder with any strength. After looking at it like a wood glue joint, making sure both surfaces were true  it worked. And to the gentleman who thought of attaching the under rib with studs from finish nails. It worked great.
 Rick

[Pukka Bundook]

Another thing I find useful when soldering, is I use a weight to hold the parts together.
After tinning for instance, ramrod pipes, I put barrel upside down in a vice, and place the pipe in position, then, hang a fairly heavy weight with a piece of wire over the pipe so it is bearing down hard on the rib or barrel.
As heat is applied, you will see the pipe settle down as the solder melts and flows. 
Works better than clamping, as clamps are only tight until the tinning melts.  Also, the wire doesn't act as a heat sink as does a clamp.

Kutter above gives very good instructions.

Richard.

[Turtle]

 Miniature "wonder bar" pry bars work well to hold pipes and lugs to be soldered. They have a notch to fit the barrel and part, and have enough spring when clamped to allow the work to settle.

[WadePatton]

...Once I realized you can't run a bead with solder with any strength. After looking at it like a wood glue joint, making sure both surfaces were true  it worked. ..
 Rick

Yes. this is key. Solder is not welding, it's hot glue of the metallic nature. Cleanliness and proper gaps get the proper wicking action.  Lugged bicycle frames were made this way (and still are in the niche markets, and also is how I built my road bike-and have cx bike fitted up).  But then silver and brass are used for high-strength joinery such as bike frames. Silver requires tighter clearances, and less heat, but brass was the industry standard for years-for cheapness of course. Craftsmen use torches to tease the flow of the solder. Industry tends to use pre-placed solder and hearth brazing with multiple heat sources. 

The only thing that changes is clearances required and the temps necessary for solders and working it properly.  Proper heat draws it, too much repels it, ride that line. Use heat to move it, not gravity so much.  Kutter covers it.

[RL]

Another thing I find useful when soldering, is I use a weight to hold the parts together.
Richard.

Thanks for that tip!