Extra Tension and how can I check it?

Might have solved the jamming in my 41. Extractor didn't seem to have much bite. Tweaked and ran 100 rounds. Nothing seemed wrong during that 100 rounds. 

what is a proper way to test extractor tension?

I generally swap out the extractor spring every year when going over my 41.. found that proper extractor setup means more than tension myself.. I've also changed over to the Volquartsen extractor
 .. on the spring call S&W customer service and they will ship you a couple if you ask.

https://www.volquartsen.com/departments/sw41_parts


if you dig around a bit you'll find some nice info from Mr Keefer on the extractor and how it should be setup

BTW you just found the source of almost all jamming issue with the 41