Few things to consider.
When welding gun parts to be blued, you really want to try and match the steel composition of the base metal. I suspect the trigger guard is made out of low carbon steel such as SAE 1010 or 1018.
I’ve seen folks used old spring wire, and coat hangers with some pretty crummy results.
Spring wire is about SAE 1095, way too much carbon.
Coat hangers are kinda like Spam; nobody really knows what’s in it. Especially those made in China, cheapest scrap the manufacturer can buy, one time use, and if they fail…which they often do no serious damage.Do not use screw stock i.e..12L14 (anything with an L), the L means the steel has lead added, which causes it to weld like crap.
So best to use simple SAE 1018, any Lowes or HD will carry it, usually called Cold Rolled Steel.
The other piece is that the welding has changes the heat treatment of the metal. So now you have hard spots (generally the welded area) and soft spots. Both will blue differently. For a quick test of this, take a case hardened part and hot blue it, it will come out a nice red color.
Best thing to do for the trigger guard is to anneal (Bring to critical temperature and allow to slowly cool) the parts. This will ensure that the entire piece is dead soft, ridding the part of any hard spots caused by welding.
Good luck,
Mike
Mike Hunter
Hunter Restorations
http://www.hunterrestorations.com
