I purchased a heavy duty extractor spring with the black insert from SAW. That spring is pretty stiff. I'm gonna go out and shoot it this weekend and see what happens.
As far as sending it back in goes, that's probably what'll happen if the new extractor spring doesn't work out. I just hate to send it back in and be without it if it's something that I can fix relatively easily and inexpensively.
Tweak- I have been working in Tucson all week and driving back up to Phoenix in the early evening at the end of my days. Today I finished a little early and got out of Tucson about 345pm and high-tailed it up to Phoenix thinking I could get to SAW by 530pm. Traffic was a mess and I didn't think I could make it in time. I didn't even get to SAW untill 10 minutes past their closing time (about 540pm). The lady who answered the door when I knocked explained that they were not open to the public (I thought they were). After I explained what I had just gone through to try and get there in time, she asked if there was something she could help me with. She let me in and took my order for (1) heavy duty extractor spring with black insert. She went in back and returned with not 1 but 2 heavy duty springs and inserts! She only let me pay for 1. I asked her of she was sure and she said "yes". This lady, I believe she said her name was Tina, went out of her way to make sure I got the part I needed after closing time. And she gave me a free spring and insert to boot! Outstanding! I thanked her for her generosity and her willingness to help me. What a sweetie she was! Now I just hope this new stiffer extractor spring works out. Are stiffer, "heavy duty" extractor springs used as standard equipment now on the shorter barreled M4's??