Mauser guys, need some wisdom

[GregM]

A few months ago I replaced the rear sight on a German K98. I had to head the snot out of the original base to get it off. My question is.....how hot is too hot to heat one of these before it affects the metallurgy of the barrel?
Thanks.

GregM

 

[Scorch]

Those sights were soldered on with lead/tin solder. Lead solder melts waaaaayy below the temp where you will start to affect the heat treating of the steel. Unless you used an acetylene torch and turned it red, it should be OK.

 

[GregM]

Thanks. I didn't heat it to the point of getting red, just used a small butane torch from Lowes. I'm going to shoot it tomorrow then, but probably will stack a sandbag on it for its first shot.

GregM

 

[Unclenick]

High power rifle barrels are typically no harder than Rockwell C scale 32, and most are several points lower. You want some hardness to have greater strength than annealed steel (about Rockwell C scale equivalent of 17), but not hard enough to make it brittle or difficult to machine. As a result, you should be able to heat it to about 1100° without affecting its temper, as it will already have been heated that high to draw it back from quenching. As Scorch suggested, that temperature will glow dull red, even in daylight.

Lead solder alloys usually melt in the 400-600°F range. Some of the ones used with steel are in the 480-520°F range because they use both lower-than-usual tin levels (maybe 10-20% range) and a small amount of antimony (maybe 2% or so). I expect these sights are attached with such a solder alloy because that type both solders to iron alloys well and does well about corrosion resistance. For that reason it is (or at least was) commonly used to solder things for marine environments.

I've done a couple of sight removals like that from 98's. I tapped them with a brass hammer to discover when the solder was finally melted, then used the hammer to drive them off the barrels. I was using an air-acetylene plumber's torch for acetylene's high BTU's (to speed the heating), but you certainly don't need (or want) oxygen. Too hot.

 

[Dfariswheel]

Also don't forget to first remove the large head screw from the front of the rear sight base.
That screw enters a shallow hole in the barrel to help align the sight base, AND it serves to hold down the front of the upper hand guard.

The original soft solder used on Mauser rifles is an almost pure lead solder that melts at lower temperatures. It doesn't take that much heat to melt it.

 

[F. Guffey]

melting point.



Tin / lead/ melting point / Brinell hardness
0 / 100/ 618.8 / 3.9
10 / 90/ 577.4 / 10.1
20 / 80/ 532.4 / 12.16
30 / 70/ 491.0 / 14.5
33 / 66/ 441.0 /
40 / 60/ 446.0 / 15.8
50 / 50/ 401.0 / 15.0
60 / 40/ 368.6 / 14.6
66 / 34/ 356.0 / 16.7
70 / 30/ 365.0 / 15.8
80 / 20/ 388.4 / 15.2
90 / 10/ 419.0 / 13.3
100 / 00/ 466.0 / 04.1

There is more to annealing and melting lead than waving a flame over or under either, and there is the time factor and heat travel, as Nick said, lead melts above 600 degree, adding tin lowers the melting point, then, at 50/50 it starts back the other way with the increase of tin.

F. Guffey

 

[Unclenick]

Thanks for the table. I'll copy that for my records. I have lists of commercial alloys, but not that nice simple layout.