Brass outer mag tube history?

[El Supremo]

Hello:
Haven't spotted anything in Marcot's book related to brass outer magazine tubes being used on some early Model 1860's.  If anyone can please enlighten us with information about why and when the switch to steel arose, it will be appreciated.  Thank.
Respectfully, Kevin/El Supremo

[Blair]

Kevin,

I can't be sure that there is a History associated with the use of brass Mag. tube housings in the actual production of these firearms.
With that being said, I can see where a seamless brass tube, of the correct size, may have been used in repairing damaged firearms when the iron/steel tubing was not available. I suspect those with brass tubes are a make-do repair.

It is important to note the Mag. tube housing is the primary compote that secures the butt stock to the receiver, along with the spanner nut at the other end.
My best,
Blair

[Arizona Trooper]

I have an 1865 rifle with a brass tube. My suspicion is that it was an attempt to fix the problem of the magazine tubes rusting into the stock. It's easy to get soapy water between the tubes when cleaning the gun. If you don't make the last step of cleaning to pull the magazine to dry and oil it, the iron inner and outer tubes rust very fast. The next morning the magazine can be stuck fast. The brass outer is more forgiving that way.

[Herbert]

I have only seen the brass outer tube on very early Spencers ,even then not all of the 6 naval rifles I have looked at did not all have the brass outer tubes and I have seen the brass outer tubes on early carbines ( these tubes that I have seen are machined every bit as well as the iron ones,so I can not say they are latter replacments or original)

[El Supremo]

Thanks, guys.  So nice to have your help. 
Regards,
Kevin/El Supremo