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Old November 5, 2008, 09:51 PM   #1
greywalker
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how to weld pins on barrel extension

Hi all, as part of a project, I am adding a jungle carbine flash hider to a no 1 mark3 that has had the barrel drastically shortened- and to be on the safe side I want to make the pinned flash hider permanent- ergo I must weld, silver solder or braze it- How best to go about that and not screw it up- what should I worry about- since this should be visible, and I have experience brazing, that is my first idea, but should I worry about overheating it or warping the barrel? how to avoid this? it should be noted that I am only brazing on pins and the flash hider, not the barrel itself....

Last edited by greywalker; November 5, 2008 at 09:59 PM.
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Old November 5, 2008, 11:07 PM   #2
PDXGS
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Find a good bicycle frame maker. Chances are they know more about brazing than almost anyone other than jewelry makers. You can use heat sinks like wet towels etc which should reduce the chance of overheating. Sorry I couldn't be more helpful.
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Old November 6, 2008, 12:19 AM   #3
Slopemeno
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Silver solder will do it. Be prepared for the bluing to be messed up enough that it will need to be reblued or Gunkoted after the fact. While youre silver soldering the hider on, you can spray break free (I'd use a spray bottle abd not from the can) into the bore to keep the scaling in there to a minimum.

I agree on a frame builder- they really have brazing down to a science.
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Old November 6, 2008, 12:55 AM   #4
DBR
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If you are only trying to make the pins permanent the best way is to TIG weld the end of the pin to the flash hider. It won't heat up the barrel significantly and it is BATF legal if that is a concern.
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Old November 6, 2008, 01:02 AM   #5
greywalker
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would a mig welder do the same thing- I have easy access to that....
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Old November 6, 2008, 01:15 AM   #6
DBR
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MIG won't be as neat. If it was me and MIG was what I had I would countersink the flash hider holes so the bead has somewhere to go. You need to run a bit hot and do it quick.

The other problem you might run into is if the flash hider is a leaded or other "free machining" steel the weld may crack. This is less likely with TIG.

Brownells sells some low temperature silver solder that will work well if you go that route. Conventional brazing is a lot hotter than necessary for what you want to do.
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Old November 6, 2008, 07:46 PM   #7
Dfariswheel
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Silver "solder" IS brazing.

Brazing, whether it's done with real silver, brass, or one of the modern alloys, is a process that needs metal to be heated to at least 1100 degrees, which is about a red heat.
This destroys finishes.

There is a SOFT solder that many people THINK is a silver solder because it contains about 3% silver.
This is in fact a true soft solder that melts at temps lower then 600 degrees.
The silver content is to make it stronger, and to prevent tarnishing like lead solders do.
Since it IS NOT a true braze material, it's unacceptable to the ATF for attaching muzzle attachments.

The least damaging method other than blind pinning is TIG welding.
Because the entire muzzle and attachment don't have to be heated red hot like with braze, heat spread is much lower, and any finish damage is limited to the immediate area of the actual weld.
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Old November 6, 2008, 08:30 PM   #8
DBR
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Low temperature eutectic alloys are available that are not soft (lead/tin) solder. I used them for high vacuum systems. They typically require 500-800 degrees. I do not know whether or not these materials meet ATF requirements for "permanent" attachment.

Here is a link to one I found: http://www.brownells.com/aspx/NS/sto...2044?%20SOLDER

Last edited by DBR; November 6, 2008 at 08:53 PM.
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Old November 6, 2008, 11:01 PM   #9
Dfariswheel
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From the BATF:

A muzzle device, such as a muzzle brake or barrel extension, which is attached to a barrel by means of welding or high temperature silver solder having a melting point of at least 1,100 degrees Fahrenheit, is considered to be part of the barrel for purposes of measurement.
A seam weld extending at least one-half the circumference of the barrel or four equidistant tack welds around the circumference of the barrel are adequate for this purpose.
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