I used the factory trigger spring on mine. The Volquartsen spring was a bit light for my preference. With the factory spring, the pull on my two Mark IV’s with the Volquartsen kit installed are just shy of 2 lbs on my Wheeler trigger pull gauge.

 

The sage advice was to use the Ruger spring, but I don't believe everything I read. So I installed the VQ spring to see for myself. It worked fine for about 8 months, and then I started getting failures to reset. I went back to the Ruger spring and haven't had any problems since. The VQ spring is just too thin to hold up for very long.

 

Here is my homebuilt Mamba. Putting it together myself was a fun project, and I have a very good understanding of how the pistol works now.

 

I like everything about this pistol, right down to the color of the grips. Very nice!!

 

Thanks guys, I went with the Ruger spring