BRAZING OR WELDING ON SHOTGUN BARREL?

[PANRA]

I have a New England Firearms Huntsman combo inline & 12 gauge rifled barrel. The shotgun barrel does not have thick enough metal to tap it for a scope mount. I bought a steal weaver type scope mount from Brownells and want to braze or tig weld it on top of the barrel. My question is will heating the metal cause the metal to lose its strength and possibly lead it to blowing up or cracking when shooting it? It would be welded or brazed directly over the breach area of the barrel. What would be better brazing or tig welding? What is the best filler metal to use?

[knight0334]

I think some of the guys over at Graybeardoutdoors.com are silver soldering a base on for those 12ga's with thin chambers/barrels.

Match fitting the base's mating surface radius and proper scoring of the barrel's mating surface should help guarantee holding strength.


Quick hits with a mig/tig welder will probably work and not jeopardize barrel integrity - but it'd probably look like shit. Brazing should be ok if you use a low temp flame and wire.

[gunfixer199]

Silver solder in my opinion would be the best I think one of the best for the job is frontlinearmory.com . His name is Rich. He does exceptional work.

[ErSwnn]

Originally Posted by knight0334

I think some of the guys over at Graybeardoutdoors.com are silver soldering a base on for those 12ga's with thin chambers/barrels.

Match fitting the base's mating surface radius and proper scoring of the barrel's mating surface should help guarantee holding strength.


Quick hits with a mig/tig welder will probably work and not jeopardize barrel integrity - but it'd probably look like shit. Brazing should be ok if you use a low temp flame and wire.

What he said. I'd be sure to have a welder with experience in such things, too much heat and the gun is screwed. You could build up the metal and then grind/file it down to look right. My concern would be the metal itself. If it's not high quality and has impurities in it such a critical and tricky spot it's going to ruin the gun. Hey! I have an idea!! JB Liquid Weld!

[PANRA]

Ok, I am trying to save money and do this myself. It is a cheap gun and I can't see putting a lot of money into it. I am pretty good at brazing copper to copper and copper to steal. Never really brazed any gun metal before though. I am pretty good with a tig welder too. I was thinking of using Harris Safety-Silv 50 brazing alloy and Harris white paste flux. I would either use an oxy acetylene torch with a rose bud tip or the tig torch might be better to concentrate the heat where needed in the shortest amount of time possible. I imagine I need to sand off the bluing around the area where I will be brazing on the barrel. I read somewhere to put a tight dowel down the barrel where you are heating to help keep the finish on the inside of the barrel from scaling. Does this sound right so far? Should I clamp the weaver rail to the barrel before brazing to help keep it in place or would that possible cause the metal to deform when heating?

Here are the specs on the Harris Safety-Silv 50

CHEMICAL COMPOSITION:
Silver 49 -51 %
Copper 33 -35 %
Zinc 14- 18 %
Other Totals 0.15 %
PHYSICAL PROPERTIES:
Solidus 1250°F (677°C)
Liquids 1425°F (774°C)
Density (Troy Oz. /cu. In.) 4.94
Color Bright Shiny Yellow White
Specific Gravity 9.34
Electrical Conductivity (% I.A.C.S.) 25. 5
Electrical Resistivity (Microhm-cm) 6.76

[justashooter]

as a CWI, welding engineer, and past professional welder i don't think you should be silver brazing on the chamber area of a single barrel shotgun. you will be going up to 1150*F to get the silv soilder to flow, and this will re-temper the steel you are soldering to. your barrel is most likely a heat treatable alloy similar to 4140 with a BHN of about 250 (WAG). if you re-temper it by silver soldering on it you will lower the hardness to about 160-180 BHN (WAG) by the refinement of grain that will occur during your soldering.

in short, you will reduce the strength of your barrel's chamber by up to 30%.

if you absolutely must scope this shotgun, you should consider long eye relief pistol scopes in 1-1.5X and a forward installation by silver soldering. the pressures toward the end of the barrel are 20% of what they are at the breech, and forward scopes swing and acquire very well. i had one forward on a 94C marlin 357 rifle. very fast acquisition. wish i still had it.

thick lines of pencil lead (graphite) will stop silver solder flow. clamp the base in place and outline it with an artist's soft graphite pencil. remove the mount and buff the contact area on both surfaces to bright. provide a feed groove on the base if you are feeding with wire. not necessary if you are using silver bearing paste. dope both surfaces lightly with flux or paste (lightly). clamp together and heat with small rosebud to dull red in a dimly lit room, testing the wire to see it if flows from time to time as you ramp up the heat.

your ideal fit is .006" clearance, so the correct base profile is important. when the temp is right the solder will wick in and flux will bubble out. a brief water quench will make the flux easy to brush off. the feed notch will stay bright after a copper brushing that should not damage your bluing much. oxpho blue will touch things up, but will not cover silver solder. black magic marker will. 1150* is above stress relief temperature, so will oxidize the bore of your barrel. chuck up a brass shotgun brush in an extension rod and spin it in a hand drill to polish bright. valve lapping compound (auto parts store) might help.

it's your face.

[PANRA]

I just purchased 1/2 oz. of 1/16 high grade silver braze alloy Silver 56%, Copper 22%, zinc 17% and Tin 5% with 2 oz. of black high temp flux for this project. It has a melting point of 145 deg. F. brazing temp, best wetting and best flow 1205 F.

I am going to look into brazing the scope base forward on the barrel for a scope with longer eye relief as you had suggested justashooter.

[ErSwnn]

Originally Posted by justashooter

as a CWI, welding engineer, and past professional welder i don't think you should be silver brazing on the chamber area of a single barrel shotgun. you will be going up to 1150*F to get the silv soilder to flow, and this will re-temper the steel you are soldering to. your barrel is most likely a heat treatable alloy similar to 4140 with a BHN of about 250 (WAG). if you re-temper it by silver soldering on it you will lower the hardness to about 160-180 BHN (WAG) by the refinement of grain that will occur during your soldering.

in short, you will reduce the strength of your barrel's chamber by up to 30%.

if you absolutely must scope this shotgun, you should consider long eye relief pistol scopes in 1-1.5X and a forward installation by silver soldering. the pressures toward the end of the barrel are 20% of what they are at the breech, and forward scopes swing and acquire very well. i had one forward on a 94C marlin 357 rifle. very fast acquisition. wish i still had it.

thick lines of pencil lead (graphite) will stop silver solder flow. clamp the base in place and outline it with an artist's soft graphite pencil. remove the mount and buff the contact area on both surfaces to bright. provide a feed groove on the base if you are feeding with wire. not necessary if you are using silver bearing paste. dope both surfaces lightly with flux or paste (lightly). clamp together and heat with small rosebud to dull red in a dimly lit room, testing the wire to see it if flows from time to time as you ramp up the heat.

your ideal fit is .006" clearance, so the correct base profile is important. when the temp is right the solder will wick in and flux will bubble out. a brief water quench will make the flux easy to brush off. the feed notch will stay bright after a copper brushing that should not damage your bluing much. oxpho blue will touch things up, but will not cover silver solder. black magic marker will. 1150* is above stress relief temperature, so will oxidize the bore of your barrel. chuck up a brass shotgun brush in an extension rod and spin it in a hand drill to polish bright. valve lapping compound (auto parts store) might help.

it's your face.

That is about as definative as your going to get. Justa, I was thinking along the lines of a jeweler's tip if soldering. Does that equate in your outline? Don't worry, no challenge here for your better knowledge and skills, justa wonderin'. I used to use one for copper sculpting with 15% brazing rod, worked great for finer work where I didn't want a lot of discolorization to surrounding metal. By finer I mean 1/8th" maybe slightly larger beads.

[justashooter]

be sure to check that your mount is steel. it may be aluminum, and that won't work at all. it will flow at silver brasing temp, and will not join.

as for selection of torch: your mount will be the heavier of the two pieces so you should concentrate on heating it more to get balance. a brasing tip or small rosebud will work. welding tips may have too much heat. the objective is to get both pieces to 1200*, and not much higher. temps too high will not allow solder to adhere.

you can buy brasing crayons in welding supply shops for a few bux that are made of wax that melts at specific temperatures (1125 is one of the standard temps they are available in). draw on the steel when cool and heat. when the wax flows you are at temperature.

[PANRA]

Well it didn't turn out too bad for my first time brazing on gun metal. I need to polish it a little then cold blue.