Scott;
Those trigger weights certainly suggest to me that someone has "fiddled" with the trigger. It's relatively easy to change the trigger return spring. They are available in various weights from Brownell's.

However, this procedure requires a person with mechanical aptitude and some experience. A pistolsmith can do it in a few minutes. I have done a number of them, but there WAS a learning curve.

Jerry Kuhnhausen's book is VERY helpful, but it is out of print and is now a bit pricy:

Dale53