A few weeks ago there was a question on barrel mounted recoil lugs. Below photo shows one I installed today. The lug is machined from a piece of C1018, with a radius to match the barrel. The two holes you see are the counterbores for two 8-40 screws that clamp the block to the barrel. (Screws are out of view) After drilling and tapping the barrel,installation procedure is to tin the barrel and the lug with high strength silver solder, then position the lug on the barrel, install the screws, and tighten the screws while heating the lug and barrel. The screws both clamp the lug to the barrel for a good silver solder bond,and hold the lug in alignment as the silver solder cools. The silver solder also wicks into the screw threads and locks them in place. Front and sides of the lug have a 3-1/2 degree draft so the barreled action can be removed from the stock after bedding. The rear of the lug is parallel to the receiver lug.

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[This message has been edited by John Ricks (edited 03-10-2002).]

[This message has been edited by John Ricks (edited 03-10-2002).]

John,

What action was this installed on?

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saeed@ emirates.net.ae

www.accuratereloading.com

John... whats the pro's and con's of heating the barrel, via silver soldering?
Does this alter the temper of the barrel, cause stress points, warp the barrel?
How does this work with barrel band front sights, and express sights, swivel bands? Thanks. ~~~Suluuq

Saeed, its a CZ550, No. 6 Pac Nor barrel, I chambered for 416 Rigby. I am also putting a lug on a 458 Lott M70 and a 450 Dakota, CZ550. The lug is 4-3/8 inches in front of the receiver. I will take a photo next week when I machine the other lugs so you can see the milling machine setup.

Rusty, this is low temp silver solder, high strength, flows at around 450 degrees. I install the front barrel band sight ramps, band type swivel lugs, and rear sights also with silver solder. Doesn't afffect the shooting characteristics or properties of the barrels.

I was a pipefitters/welders helper for two summers in college. The main help in stress relief of welding and soldering is to heat the part evenly around the circumference of the barrel (even if you are just installing a saddle like the barrel lug above) and to let it cool as slowly as possible. We used a thermal blanket to wrap the welded area to slow down cooling. In critical situations we'd wrap the fitting/pipe in a heating blanket, keep it at 600 F for 24 for hours, then bring it down slowly over another 24 hours. Obviously for low-temp solder (held by screws) I'd use a 450F initial temperature, then hold it at 400F for a few hours then bring it down slowly.

I have a take-off Win M70 barrel in 416 with a recoil lug that was WELDED on crooked by the factory that I want to try this on. It walked badly with heating during the first three shots, but shot in the .3s after that. It seems to be worth rescuing if possible.

Don

I always enjoy you photos John. Thanks.

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NRA Life member

Interesting thread. In truth 450 degrees F is above the tempering temperature of SAE 4140. Therefore, you are charging the temper of the steel somewhat.

Don G,
What you are referring to sounds like working with iron pipes. That is the same process used when welding iron pipes albiet the temperatures are a bit higher. Essentially what you are describing is an annealing process. You are stress relieving the material and softening/weakening it too. There will also be a heat effected zone then where the annealing area's effect stopped. This condition creates a stress riser. If you have ever seen a failed weldment you have probably seen this first hand. The weld will fail in the base material slightly away from the edge of the fill material. The heat effected zone created by Don G's approach will be less severe than the typical weld though.

Whenever, you heat a piece of steel and allow the temperature to come down slowly or quickly you are affecting the steel's properties. The big issue with soldering isn't so much that you are weakening steel to an unsafe degree, but that you are relieving internal stresses in the steel and warping the barrel. Now if someone overheats the barrel there can be a dramatic difference in the microstructure of the steel which will greatly affect the strength.

Todd E

[This message has been edited by Todd E (edited 03-11-2002).]

Ya gotta remember surface temps, I can hold my hand on the barrel a couple inches away from the lug when heating the barrel. The object is to heat the surface just barely enough so the low temp solder will flow. I use a low temp Prestolite soldering torch, soft acetylene only flame, no Oxygen. Plus I slow cool it under a infared lamp. This is the old "sweating" menthod for you gents that have held a torch. With a properly stress relieved barrel, this small amount of heat will not warp. Plus, the proof is in the shooting, last 458 Lott I installed a lug on was shooting 5/8" groups, iron sights, at 65 yards, 500 grain full loads. I am thinking of putting a scope on it to see just what it will do at 100 yards.

Another thing to remember, if you are experienced in heat treating and know your tempering colors, a good 450 degree soak turns the surface a light straw color. I get no discoloration, the barrel remains polished bright, which is a good indication of minimal heat input. Besides, this method has been used for generations for installing barrel accessories with no ill effects. Like Don said, even heating around the circumference is required. Of course, if the inexperienced tried sweating with a oxy/acet torch, barrel damage will likely occur due to the intense heat.