Howdy,
Well, I run .5 ohm as well, you said it was an 18650 box mod, 1 battery or 2xStacked (just trying to get idea here).
If its 1 battery then your pushing 34w on a fresh battery, this may not seem like a lot but can run a little toasty, this is also assuming that your using a fresh battery each time and the box is not regulated.
Ok, so....
Lets say its 2xstacked.
4.2v x 2 = 8.4v, if I follow ohm's law and assuming that nothing has changed that is 141.2w on 2 fully charged batteries, that is well beyond the burn point of juice.
Basically what I was saying is to be careful on unregulated mods, if you can't adjust your mod (PV) electronically then you could be playing a cat and mouse game of vaping.
1.6 ohm will yield 44.3w on two fully charged 18650's, so that will drop down the temp to a warm vape, nothing too hot and shouldn't even get close to cooking your juice.
Use this link to adjust your coil to your mod, you'll find it wonderful to get that amazing vape each time. I used to spend seconds on coils and wonder myself, then I realized that the atomizer is in truth the most complex part but the one that can be heaven if you spend just a little extra time on it all.
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Hope this helps,
Sincerely,
Midnight