Permanent attachment

[CAR-AR-M16]

It shouldn't bother it. To anneal 4140 which I'm guessing most mil spec barrels are made from (or something close to it) you have to go to about 1600°

The actual milspec for an M16/M4 calls for 4150. Many commercial barrels are 4140.

[Hump66]

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 1800 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.

Just random thought, would adding glycol(antifreeze) to the water help/hinder me in controlling heat transfer?

[Sanjuro82]

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.

[tyromeo55]

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

[Boehlertaught]

It shouldn't bother it. To anneal 4140 which I'm guessing most mil spec barrels are made from (or something close to it) you have to go to about 1600°

I think you would also have to have the barrel hot for a number of hours to anneal the metal.

[Sanjuro82]

I think you would also have to have the barrel hot for a number of hours to anneal the metal.

You'd have to take the steel to critical which for 4140 or 4150 would be between 1550-1600 degrees. Then to anneal the steel you have to allow it to cool very slowly over a number of hours.

[Shadowrider]

I think you would also have to have the barrel hot for a number of hours to anneal the metal.

Only to reach 100% total heat saturation. Then like Sanjuro said, cool it very slowly over a number of hours.

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.

Tempering and anealing are as different as black and white.

If you are losing hardness (temper) you have gotten to critical temp. If you use a torch it's quite easy to get the surface and slightly below it (where you hardness testing it later) to critical. That may be why you've seen it happen. Also that's why almost every heat treat specification I've ever heard of specifically forbids open flame furnaces, among a myriad of other reasons. You can put the barrel into an electric oven and subject it to no more than 1100° and leave it for days. Cool it down slow, and you won't lose any hardness.

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

Good idea, if you can control the heat.

[Shadowrider]

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.

lol. I hear ya, that chit's soft and stringy. The only way to get it shiny and purdy is to use coated carbide and run 900-1100 SFPM. Damn near impossible to do on a manual engine lathe. One of the 1213s is much easier to machine nicely.

[Hump66]

Well, I've tried 3 times now with the silver solder with mixed results. Each time it holds better, I guess I'm just paranoid about damaging the barrel. Now I'm wondering if the multiple heat/cool cycle could have done anything. Any thoughts?

[HiredHand]

Hump66, maybe you need some TempLac or similar product.

[HiredHand]

http://www.tempil.com/products/tempilstik-original/

Temperature indicating marker.

[Hump66]

I think for the $128 markers, I'd just take it to a gunsmith. Those are a cool product though. I think I may try once more and then order the tempilaq liquid.

[HiredHand]

I thought you had to use silver braze for permanently attaching the muzzle device.

[Hump66]

silver solder is what the ATF requires. I bought a syringe of it in paste form, just smear it around the threads and heat it up.

[tyromeo55]

Well, I've tried 3 times now with the silver solder with mixed results. Each time it holds better, I guess I'm just paranoid about damaging the barrel. Now I'm wondering if the multiple heat/cool cycle could have done anything. Any thoughts?

What are you using as a heat source?