Soldering question

[Bigmon]

I have round barreled rifle that one of the underlugs came off.  I did not do this one , but have done a few and never had one come off.
So now I am fitting a new one on.
Problem is, can't get the solder to stick.  I have used up the last of what I had used with good results before, and have been unable to find it anymore.
I understand that now it is made without lead?  Could this be the problem?

I do have a very old roll of "KESTER" ACID CORE SOLDER.
It says nothing about having or not having lead?
The other stuff I was using was not acid core.  Would this acid core be ok?
If I remember from shop class half a century ago that the acid was just a flux?
I use flux anyway???
Any advice would be welcome.

[B.Habermehl]

I’ve used modern plumbing solder with no problems. Clean everything to a clean filed surface. Flux with plumbers flux from the hardware store. Heat the filed and fluxed lug and tin with solder, do not overheat and burn the flux. Shake excess solder off. Flux the barrel and clamp the parts together and heat the barrel till the joint wets. Add a bit of solder and we’re done. Probably takes me about the same amount of time to do this as writing this post with my hunt and peck typing. BJH

[Bigmon]

Thanks BJH,
That is pretty much how I did it before and it always went well.
For some reason this is not.
I was trying a finer flame Butane torch.  Maybe not hot enough?
Went back to my usual little propane torches, and they are messed up.  Will get a new one this morning.

While writing this my brother just called me and he has a roll of 95-5, which I believe contains lead.  Would that work easier?

Also have a roll here I thought was solder, but it is called "LEAD LASHING WIRE"?  What on earth is that?  Looks and feels like solder, but I don't think it is??
Thanks as always.  I am always learning and re-learning.

[Blacksmoke]

Bigmon:  95-5 solder is lead-free that is what the plumbers use now for copper pipes as lead solder is banned in the plumbing industry.  95-5 is: 95% tin and 5% silver - it is twice as strong as the old 60-40 leaded solder.  Just use regular paste flix with it and make sure that your surfaces are bright and clean.  Also use sufficient heat source and heat up the barrel first then apply the barrel lug. You could "tin" the two surfaces first the sweat them together using a propane torch.  Good luck,  Hugh Toenjes 

[P.W.Berkuta]

For me the 95-5 is: 95% tin and 5% silver plumbers solder works well on copper pipes but I don't have good luck with it on steel. I use either Stay-Brite with its flux (paste) or good old 50/50 plumbers solder with its paste acid flux. Your KESTER" ACID CORE SOLDER should work but I would get a small container of the acid flux and apply it liberally to tin the two surfaces before joining them with heat.

[Dave B]

One thing that may help is to tin the area using steelwool dipped in the paste once you have the area hot enough to melt the solder on the area of the tab. Scrub the hot surface with the steelwool. It will tin the area with a thin layer of solder. Do that same tin layer on your tab. Done this way makes it easy to join the two. Cliff Noll discribed how he solderd his sxs shotgun barrels ribs using this technique. He added the use of two slugs of copper on a steel rods heated to slide up and down the bore to heat the barrels inside and a propaene torch outside. The solder flows like magic. The trick is not to get too much heat and burn your flux.

[Blacksmoke]

Do what Dave B. says - it' works well for me too!

[Bigmon]

Thanks to all, I am gonna get at it and see what happens.
I never had any real troubles before, have soldered lugs and sights many times.
But this just doesn't want to hold?
Thanks again