# Silicon Bronze TIG brazing gun barrel



## epanzella (Dec 23, 2018)

A rifle I'm building needs a scope base securely attached to a a 4140 chrome moly barrel. I have been told a standard TIG weld will alter the 4140 making it unsafe for high pressure loads. Will TIG brazing the base with silicon bronze rod avoid altering the base metal?


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## benmychree (Dec 23, 2018)

In a word, NO.


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## Nogoingback (Dec 23, 2018)

Bronze welding (some times called brazing) is used exactly for that purpose in some applications.  An example is welding thin wall
chrome moly motorcycle frames, although it's usually done with a torch rather than TIG.  Because it's a lower temperature
process, and because the base metal isn't melted, it doesn't alter the base metal properties.  Instead, a fillet is created which
joins the tubes.  It's used to avoid cracking at the welds.

Whether this is suitable for your application is another question.


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## benmychree (Dec 23, 2018)

Silver solder, done with torch heat, might be another approach, especially in a low temperature formulation; I think it would depend on whether or not the barrel is heat treated.


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## 682bear (Dec 24, 2018)

TIG brazing, if done correctly, will not melt or alter the base material... if done correctly...

I have done a fair amount of TIG brazing with silicon bronze and have discovered that it is tricky at best to do without some amount of melting the base metal, sometimes I can do a decent job, sometimes not so much...

Silver soldering would be better, or drilling and tapping blind holes, if you have enough thickness is best.

I have d&t holes for sights in barrels a few times. 

Just out of curiosity... what is the reason for putting scope mounts on the barrel?

-Bear


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## Dabbler (Dec 24, 2018)

This CANNOT BE DONE SAFELY.  In order to mount, for instance a Picitanny rail to a barrel - which I have done several times - you make a clamp that is .002 oversize and secure with a screw that compresses the barrel.

Applying any heat over 450 degrees F  will alter the het treat ot the barrel.  period.


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## epanzella (Dec 24, 2018)

You guys have convinced me. My TIG won't get near that barrel. Thanks to you all and Merry Christmas.


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## epanzella (Dec 24, 2018)

682bear said:


> TIG brazing, if done correctly, will not melt or alter the base material... if done correctly...
> 
> *Just out of curiosity... what is the reason for putting scope mounts on the barrel?*
> 
> -Bear


I'm converting a Break open shotgun to a 45 caliber smokeless muzzle loader by a process called stubbing. The original barrel is cut off at the hinge pin. The factory 12 ga chamber is bored and threaded then the barrel blank is threaded to go inside it. A shoulder is left on the blank to butt against the original part of the barrel. The last step is to bore and thread the barrel blank at the receiver end for a breech plug that will take a shotgun primer. There is no place to put the scope mount but on the barrel.


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## 682bear (Dec 24, 2018)

Ah, I got it... my dad has built several of those... he puts iron sights on his.

-Bear


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## 682bear (Dec 24, 2018)

Double post for some reason?

-Bear


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## epanzella (Dec 24, 2018)

682bear said:


> Ah, I got it... my dad has built several of those... he puts iron sights on his.
> 
> -Bear


My iron sight days are long gone. Merry Christmas Bear.


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## derf (Dec 26, 2018)

I've done about 35 like that. Drilling and tapping works fine.


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