Wellllll..... I actually got an "m" wae this week and it's used. You are correct about the run time, with the spring that is. I ended up soldering a brass nut to the bottom of the tube. This direct connection with the battery allowed me to get
through a full work day on one 18500. Significant difference. I also noticed that you had an efest 18500 in a picture. My efest 18500 is horrible compared to my 1200 mah aw 18490
batteries. So an 11 hour work day on one aw 18490 compared to 4 hours with the copper spring.