Silver soldering? Brazing?

A

Aguila Blanca

Staff
I know that Springfield Armory (the modern company) uses or used to use two-piece barrels on many of the 1911s. The outer portion in the chamber/barrel hood area is a sleeve that's fitted over the inner portion of the chamber -- the actual chamber -- and then (from what I've read) silver soldered in place.

I have an off-ball project in mind for which I'll need to do the opposite -- make a chamber insert so that I can chamber a shorter cartridge of the same caliber. I think I can muster the metalworking skill to make the insert, and I have access to a lathe. What I'm clueless about (other than life in general) is how to install the chamber insert in the barrel. I assume silver soldering is the way to go, but I don't know how to do it.

Is silver soldering the same as brazing? Is it the appropriate technique for mounting a chamber insert?

Advice appreciated.
 
B

Bill DeShivs

New member
True "hard" silver soldering is similar to brazing.
Silver solder "wets" and flows when it is melted. It requires a special flux and high heat- 1200 degrees or more.
Don't confuse hard silver soldering with the 4% silver-bearing solder sold in most hardware stores.
 
T

tangolima

New member
Brazing or silver soldering is too hot. It would alter the barrel's heat treat. Soft soldering or even epoxy is better.

-TL

Sent from my SM-G930T using Tapatalk
 
J

Jim Watson

New member
Is the caliber conversion you have in mind a secret?

The MC Ace inserts .30-06 to .308 to 7.62x39 are held in with Loctite.

The Navy inserts .30-06 t0 7.62 NATO are interference fit by a particular procedure.

The Chilean inserts 7mm Mauser (rebored) to 7.62 are soft soldered and not real strong.

I don't know how the 1903 FN 9mm Browning Long to .380 inserts are held in, maybe by interference fit as Maj. Geo. C. Nonte described for converting 9mm Largo to 9mm P.

Most full chamber bushings and full length linings are held with Loctite these days, although they used to be soft soldered.

Monobloc shotgun barrels are soft soldered.

Silver solder or furnace braze like IMBEL and FN is a factory level operation that might be beyond a small shop and certainly a challenge for a DIY.
 
H

HiBC

New member
I don't know anything about what you are doing.It might be fine.Here is something to think about.
If you are looking at a semi-auto handgun barrel,they do not typically over-engineer surplus steel into the design.
So now you bore your hole to push your insert into.
Where you end your bore,at the place your insert stops,you have an inside corner.
That inside corner is a place where the steel is the thinnest.What will the material thickness be at that point? By what percentage has it been reduced?

That inside corner is a stress riser. It not only gets the pressure loads at firing,
it structurally absorbs the other mechanical forces of firing.Slide action,barrel harmonics etc,during recoil.
I'm not trying to rain on your parade,I just suggest you carefully consider the steel around that inside corner your boring bar leaves at the step.
 
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T

T. O'Heir

New member
Generally speaking chamber inserts just don't work. The Navy inserts Jim speaks of tended to come out, without warning, upon extraction.
Loctite stops locking tight when heat is applied.
"....30-06 to .308 to 7.62x39..." Doesn't work anyway. 7.62 x 39 uses a .311" bullet. And it's rim is bigger.
 
J

Jim Watson

New member
I know the Navy inserts were somewhat subject to pulling out but don't know the rate.

There is a 450F grade of Loctite that would hold up in any manually operated gun's barrel. I don't know if that is what MCAce provides.

As P.O. Ackley said, by the time a slightly oversize bullet travels its own length, it will FIT the barrel. At one time Ruger Mini 30s had a long leade into a .308" barrel.

The rim of a 7.62x39 is smaller than .308. Maybe not so small that the extractor won't grab.
 
M

Mobuck

Moderator
Locktite bearing and stud retainer will stand far more heat than anything short of continuous full auto gun fire will generate.
I mounted some dual hub spacers using this product about 25 years back and recently had to remove those bolts. The heads of the 5/8 fine thread bolts were heated to glowing red multiple times before finally popping loose under 700# of torque applied by an impact wrench.
 
U

Unclenick

Staff
Aguila Blanca,

Given the skills involved, unless you want to work on developing those skills, you would be better off to buy a barrel already chambered in your desired caliber or one with no chamber and get a chambering reamer for your cartridge and cut the chamber yourself.

I had one of the Springfield Armory barrels at one time. It had a copper-colored ring at the braze line, so I believe it was brazed with an alloy like very low tin bronze. This would probably have been done with an induction heater, possibly simultaneously with heating of the barrel for quenching and drawing back to final temper in a hydrogen atmosphere oven. Not something the average person can do conveniently.

The difference between soldering and brazing is generally just a matter of what temperature range is employed. I was taught that If it is at or below the melting point of lead, it is soldering, and if it is higher than that, but below the melting or fusing point of the metal parts being joined, it is brazing. I've also read that 840°F is the dividing line. Both brazing and soldering join metals that melt at a lower temperature than the metals being joined. Silver soldering is properly called silver brazing, as it happens above the melting point of lead and above 840°, both.
 
F

F. Guffey

New member
The 308W case is .014" larger in diameter at the shoulder/case body juncture than the 30/06 case and I wondered just how thin was that insert. It just seemed to me at the time there were a lot of people talking about it and repeating information from someone claiming he was an arsenal-est. .

There are claims made by shooters it is possible to shoot 308W ammo in a 30/06 chamber, I believe it is a bad habit because the 308 W has to be sized when the bolt closes, the interference fit between the 308W case and 30/06 chamber allows the case to head space at the 308W shoulder/case body juncture.

Now, tell me again how the insert makes the 30/06 chamber larger?

F. Guffey

This reminds me of the movie 'MY COUSIN VINNIE', that would be the part about magic grits.
 
J

Jim Watson

New member
The shoulder-body juncture of the .308 is also farther back down the body taper.
I don't have the capability to overlay exact same scale drawings to see how that affects the nominal fit, but I have seen enough pictures of .308s fired in .30-06 chambers to know that it can be done. Habit? No, usually just carelessness or maybe excess curiosity.

The Navy 7.62 insert was installed after reaming the '06 chamber with a maximum or even larger than maximum '06 reamer to allow for a more substantial insert and a uniform fit. It was hammered into place with a couple of proof loads.
MC Ace is not going to tell you to do all that, they advertise pulling their insert out of the Loctite with a broken shell extractor so as to return to the original ammunition. Be interesting to see their insert and to see some fired cases.


And we STILL don't know what insert to and from the OP plans.
 
F

F. Guffey

New member
This reminds me of the movie 'MY COUSIN VINNIE', that would be the part about magic grits
Click to expand...

The chamber diameter of the 30/06 is smaller in diameter than the 308 W chamber. Meaning the 30/06 chamber has to be cut before the 308 W is inserted. If for some reason the insert is opened up and the 30/06 chamber is not modified reaming the 308W insert will be cut into two pieces. Back then I suggested reloaders/smiths ream the chamber to 30 Gibbs when cleaning the chamber (after removing the insert).

Again; there is no clearance when a 308W round is fired in a 30/06 chamber, the fit at the junction is a crush fit, I will never know how that story ever got started with 'all you gotta do is...' shove an insert into the chamber and glue it.

Free bore:eek:
 
U

Unclenick

Staff
Mr. Guffey is correct that the shoulder/body junction OD of a .308, at 0.454" maximum diameter, exceeds the minimum diameter of the .30-06 chamber diameter at that same location forward of the breech, where it would be 0.4487". However, a minimum diameter .308 case would be 0.446" OD at that shoulder/neck junction and a maximum .30-06 chamber would be 0.4507" at that location. A case and chamber at their half-way tolerance points would have just 0.0003" interference which you would barely notice upon closing a bolt, so you can see how many might be lead to believe there is room for a fit by trying an actual .308 round's fin in and actual .30-06 chamber. It's just never going to be a reliable possibility, and you don't want to make an adapter that is 0.0007" thick at some point along its side to convert a maximum .30-06 chamber for an average or lower diameter .308 round.

I've seen a .308 inadvertently fired in a .30-06 chamber, but it depended on the chamber being loose enough, the .308 undersized enough, or the bolt being able to wedge the round in. The bullet had low velocity (dropped below a small 50 yard target) and the case extracted with no neck; just a rounded shoulder leading to the mouth.

MC Ace makes adapters for 7.62×39 for either .308 or .30-06 chambers. There is a question on their site asking "how about .308 in .30-06", but no answer and no such product listed that I could spot. The price below the question is for 7.62×39. If you had a wide enough .30-06 chamber, I suppose you could Loctite just a false shoulder in place to stop the blowing forward that I mentioned before, and to bring the pressure back up, but you would want to be sure you had the space in your chamber to do it, first.
 
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