Try Nevr-Dull wadding and a bit of force to remove the arc-glazing. If you are a mech head you should have a can of it anyhow, it is cheap and great for removing tarnish or patina. Make sure the firing slug battery contact is clean, dead level, and isn't pitted -judging from the construction of that switch, builds below .25 ohm are going to give it some serious pitting unless it is rhodium plated (doubtful). Make sure the outer circumference of the firing slug is completely clean, as well as the inner portion of the battery tube it contacts; this connection is essential for the
mod to fire well, keep it doped with a conductive grease like noalox gold.
That vdrop is pretty abysmal. For accuracy, you may want to repeat your tests with a 1 ohm load. Measuring the resistance of a
mod (part of what creates the voltage drop) is complicated by the voltage sag a low resistance atomizer creates on the battery when it is fired. Since a higher resistance load creates less voltage sag, when you measure vdrop you will be meausring more of the drop created by the
mods resistance, and less of the atties low resistance creating voltage sag.
In my experience, stainless steel to brass electrical connections work quite a bit better when they are doped with noalox gold or a similar conductive grease, I feel this is important enough to mention a second time here. I have a SS prax1s clone that has a brass firing slug, mechanically and electrically, it is pretty similar to the skyladon's switch (i don't own a skyladon, but there are a lot of pictures on Google images), and my prax1s hits hard even at .14 ohm.
If the stingray you ordered is 1:1 you won't be disappointed, it's switch is easily in the top 3 for tube mechs running atties close to, or at battery CDR.
