Repro frame alloy?

[Rex Northen]

Great information here - thanks for sharing!

[Chuck Heald]

Originally Posted by Linn Matthews

Edgar
Thanks for your note. Would you please comment re your thoughts of what treatments would produce the best receiver?
Thank you

Linn

In modern guns, the receivers are often made of 4140 hardened and tempered to mid 30's Rockwell C scale.

The RBL is an example of a 4140 frame. On my visit to the CSM plant, Tony told me that they pre-hardened/tempered the frame blanks prior to machining. This did two things for them.

First it reduced the grain size of the steel and allowed for finer finish of the machined surfaces. Normalized 4140 machines poorly and leaves a rough finish. Slightly hardened, it machines with fine finish, albeit it takes a bit more energy to cut.

When a part will never be welded, 4130 and 4140 can have a small amount of lead added as an alloy to facilitate better machinability. This addition doesn't affect mechanical properties much from a practical standpoint. However, the RBL has a welded on upper tang.


Second, it eliminated distortion from heat treat after machining.

[Autumn Daze]

I believe the same holds true for 200 series Stainless Steel. I remember machining 203EZ Stainless and it left great finishes. There are also some leaded low carbon steels that machine great but I can't remember the series. Chuck you might be right about 4140 for the Repros. But it does machine lousy.

[Chuck Heald]

Dave
I've made some parts from leaded mild steels in the past.

This is a triggerguard and floorplate on a custom Rem 600. I whittled it from a solid block of 12L14. and hand filed the curvy stuff. The stuff machined about like aluminum.

[edgarspencer]

Great looking trigger guard!
Finding any alloy steels with either lead or selenium today is nighon impossible. I used to produce a 303 stainless, but just having selenium on hand was a liability.
Did you ever notice how the higher grades differ in case colors from the lower grades. I have always believed that the engravers, whether in-house, or contract, refused work on the more hardened actions based on the time and graver tool wear. The frames, naturally were always the same base material, but the secondary heat treatments given must have been either annealed or drawn back to allow the engraver something softer to work with.
It doesn't surprise me that Galazan uses 4140. It would most certainly be the billet of choice for strength and ductility.
I regret not having more interest in the materials used by the old-time makers, as I had both an optical emission, and xray fluorescent spectrometer in my lab, not to mention the ability to photo-micrograph materials to see their grain structure. Hardness testing wood have involved leaving a tiny braille mark, but I could have done it in an engraved aread and the teeny dot would have blended right in. Maybe in my next life.

[Autumn Daze]

Edgar, Thank you for your input. I always learn from it......

[Chuck Heald]

Edgar,
We had a guy on the doublegunshop board 4-5 yrs back that was the manager over the lab at a metals outfit, I think up in Oregon (Ti was their specialty), that wanted to do a bunch of testing of samples from barrels of doubles. I made the tensile (hoop) test fixture. Many members contributed samples. Shortly after I sent the fixture to him, he fell off the radar. Woulda been fascinating to have seen the metallurgical and mechanical data.

[Chuck Heald]

Looking at that picture of me holding that RBL frame makes me think that may be steel extrusion.

[Autumn Daze]

Chuck, I sent that gentleman several samples of different types of Parker barrel steels. I have his contact info but he has never replied to my emails.

[Chuck Heald]

Makes me think something bad happened. A couple of us were in daily contact with him until ... nothing.