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Discussion in 'NFA & Class III Discussion' started by Hump66, Aug 17, 2012.
Look into a reamer set =)
300 series stainless sucks to machine anyway, though 304 isn't as bad as some. 316 sucks azz.
Yeah there's a lot of info on another forum I've been reading up on. Sadly my first attempt last night failed, not enough heat. Gonna clean it up and try again. I got the silver paste from a shop here locally, it's actually a 1240* melt, 60 something %.
It can harm the heat treat, but done correctly the heat treat can be left pretty much unharmed. Most barrel are 4141 or 4150 and once you get above 500-600 degrees that type of steel will begin to temper. Disregard the annealing comment. Most folks can be a bit confused with heat treating. In particular terms like tempering and annealing can get mixed around. An annealed piece of steel is one that has been heated up to critical temp (the point at which is loses magnetism), and then it is cooled very slowly. When annealed properly, the steel will be in it's most mailable and soft form at room temp. Critical temp will be well above 1600 so annealing won't come into play unless you bring the whole barrel up to cherry red.
You could lose up to 10-30 off the Rockwell if you bring the barrel up to 1100-1200 degrees carelessly. To minimize the loss of the barrel's temper there are a few things you can do to.
1. Heat the muzzle up as quick as possible by using an oxy-acetylene torch. The longer it takes to get to the soldering temp, the more heat will be transfer down the barrel. Heat transfer is what you want to minimize.
2. Use a heat stop paste on area of the barrel that aren't being soldered.
3. The barrel/rifle (minus the muzzle) can be suspended in water, again to prevent/slow the heat transfer down the barrel.
I spent my reamer set money on the A/C repair man.
I don't mind 304. 316 is definitely less fun to machine. I'll take either over 1018. Might as well chuck up some hamburger meat and try to cut on it.
The actual milspec for an M16/M4 calls for 4150. Many commercial barrels are 4140.
Just random thought, would adding glycol(antifreeze) to the water help/hinder me in controlling heat transfer?
Not sure on that, but regardless it wouldn't be necessary. So long as you follow the standard procedure you won't mess with the tempering too much. Just don't over heat it, or don't heat it for too long of a time period. Basically you want to heat up to the temp that allows the silver solder to flow and that's it. Anything you can do to speed up the process (without sacrificing a through and complete solder joint) and to prevent heat transferring down the barrel would help with retaining the heat treat of the barrel.
ya know Ive been pondering this for a moment and think that if a guy wanted to do quite a few of these he could get a small coil induction heater hang the gun upside down and place the 1100 deg solder ( formed into a ring ) against the ridge of the flash hider. Heat just long enough to melt the solder. The induction coil will place a very focused heat, would do it very quickly and could be turned off the instant the solder melted. also, Ive got a pretty good idea on where to source an induction heater on the cheap if your handy
I think you would also have to have the barrel hot for a number of hours to anneal the metal.