ALLOY FRAME

[jdowd]

I have an early model 39 with what appears to be an alloy frame. Exactly what metals are used in the alloy frame? It is slightly magnetic and the S&W letter sheds no light on the nature of the alloy.

Are alloy frames normally slightly magnetic?
Thanks for any assistance.

 

[barbara_em]

A strong magnet will pick up on the metal parts within the aluminum frame, trigger bar, mag release, mainspring, side plate, etc. Stripped of these parts, the frame itself is non-magnetic. (I don't teach science, but the guy in the classroom next to mine, does.)

 

[kwill1911]

It is aluminum. Please share the letter and SN if possible. There are a number of collectors interested in the early pistols.

 

[barbara_em]

I remember when Colt used to advertise Colt-alloy while other manufacturers talked about aircraft quality aluminum. That phrase usually refers to 7075. I know that alloy's used in some M-16s. If it's in other firearms (Colt Commander, S&W Airweights, etc), I don't know.

 

[S&W59]

If its 7075 aluminum then its a primary alloy of zinc and aluminum with a smaller composition of copper and magnesium. This results in a very hard alloy, comparable to steel. There is some oxidation issues with this alloy if not kept clean and lightly oiled. This isn't rust but a differentiation of color seen as freckling or spotting. Left unchecked it will pock and pit the finish.

 

[barbara_em]

If its 7075 aluminum then its a primary alloy of zinc and aluminum with a smaller composition of copper and magnesium. This results in a very hard alloy, comparable to steel. There is some oxidation issues with this alloy if not kept clean and lightly oiled. This isn't rust but a differentiation of color seen as freckling or spotting. Left unchecked it will pock and pit the finish.

I assume that it's a different alloy used in garden variety guns, then. There are a lot of members here who have polished the anodized coating off their S&Ws for a bare finish and don't have the issues you mention.

 

[JohnHL]

I assume that it's a different alloy used in garden variety guns, then. There are a lot of members here who have polished the anodized coating off their S&Ws for a bare finish and don't have the issues you mention.

All aluminum alloys will oxidize if left exposed to the elements (especially air which is approx. 20% oxygen).

As long as a light coating of oil (or anything which will protect the surface) is kept on the finish (as is the wont of most gun owners), they will remain shiny.

John

 

[Mrnurse]

7075 aluminium alloy's composition roughly includes 5.6–6.1% zinc, 2.1–2.5% magnesium, 1.2–1.6% copper, and less than a half percent of silicon, iron, manganese, titanium, chromium, and other metals. It is produced in many tempers, some of which are 7075-0, 7075-T6, 7075-T651.

The first 7075 was developed in secret by a Japanese company, Sumitomo Metal, in 1943. 7075 was eventually used for airframe production in the Imperial Japanese Navy.