I don't like parallel 18650 in Mag. Parallel cells physically, not electrically.
I'll explain.
As per Gtamazing problem, seemingly stuffing tube is not reality.
26500-26700 cells fit inside tailcap using shortened spring.
18650s singles also fit inside cap. Parallel 18650s don't fit inside tailcap.
So 2D mag can fit 2 x 26650. I have 3D 64623 mag with 4 x 26500, very short tail spring but in the standard spring holder.
With 18650s single file, Mag 2D - fit 2 cells, 3D 3 cells, 4 D 4 cells, 5D 5 cells. 6 won't quite fit in 6D, need small extension.
Not speculation, I have done all combos.
To use single file 18650s, remove anodizing from inside of cap and use a C spring, shortened if needed. C springs cost 50c I think.
You can do super neat job, mask off, use caustic , or just stick a wire brush in a drill and remove ano ion 10 secs.
Use some rough grit and hand for 30 second solution.
Simplest of simple mods and super cheap. Fit D spring back at any time.
Standard mag body length, twin bored:
2D fit 2 x 18650 - no advantage.
3D fit 4 x 18650 - 1 cell advantage.
4D fit 6 x 18650 - 2 cell advantage.
To get above advantage, both twin boring and a cell holder is required (and has to be paid for)
Unless you have tube re anodized, you now have a conductive section of tube resting against your cells. If the cell wrap gets damaged....
With parallel cells it's still a tight fit in bored Mag. The only time I have ever worn shrinkwrap of cells is when using twin bored mag and parrallel cells/holder.
Damage done by the threads on tube. Also the small step in body just past the threads.
Depending on requirements for light, current cell availability make me think 2D mag with 2 x 26650 cells is a simple cheap way to get good capacity inside a mag easily. 4000mAh cells about $15 each.
Sleeve for cells and tailcap ano and short spring mod. Insert 2nd sleeve to use 2 x 18650 if needed.
