Just for clarification, the Brownells gauge (I have) is a Manson. I think the spring the original post refers to is the spring loading of the plunger in the dial gauge. This is the only spring present and is very light. It is built into the dial gauge and cannot be strengthened as it works through the light precision mechanism of the dial gauge.

The Brownells/Manson gauge is as I said above quite tricky to use, but with care I'm able to get consistent results and it is very much cheaper than some of the more satisfactory offerings I have seen (which are often many times the price).