Something isn't right somewhere...
I'm currently running dual 8 wrap KA1 24/32 3mm i.d. Claptons on a HOG V3 at around 0.47. A 10 wrap 3mm i.d. single coil will definitely be above 1 ohm, but there is no way it should be 2.4. The same with that 2.5mm i.d. coil - a reading of 1.8 is way too high. You seem to be getting a reading of almost double the resistance I would expect from those builds.
I would first check the legs are securely clamped by the grub screws (check the screws aren't 'nipping' the edge of the coil leg), check the atty 510 is clean and the pin isn't loose - also check it on a mod if you haven't already to make sure you are getting a similar resistance reading on both the mod and 521 tab are similar. It could be your build tab is faulty (also make sure the 521 build tab 510 is clean!)
Bear in mind that 521 build tabs can only give battery voltage output to the coils - with a fully charged battery and a 1 ohm coil that is an absolute max of 17 Watts. If that 10 wrap coil you currently have fitted really is 1.8 ohms (which I seriously doubt) then your 521 tab won't be capable of much more than 9 Watts - you will die of old age before that coil actually glows.
Build tabs are good for glowing typical lower ohm DL builds and small higher ohm, thin gauge wire MTL builds , but they AREN'T any use for glowing high mass, high resistance multi-wrap coils - a single 18650 can't provide the voltage you need to glow that amount of metal, and build tabs don't have voltage boost circuitry so they are only suitable for resistance checking when it comes to large high resistance coils. You are going to have to use a mod to glow that coil - if it is a single battery mod it MUST have boost circuitry, but a dual 18650 mod is far more suitable.
