stranded wire is 20% more in cross section compared to the same AWG solid. When you crimp you crush the wire into a cold weld, stranded or not the copper content will be what it is, the air does not count. I have always had to strip 16AWG cable with 18AWG strippers, and that includes the air. The tool is 1mm in diameter which is 0.75sqmm not 1.3sqmm gaps in the stranding included, other 16AWG strips with 16AWG strippers.
There is zero chance that they are fudging any numbers. The military would skin them alive if they tried to pull any shenanigans. This isn’t a Chinese fly-by-night, it’s a huge company with a reputation to maintain.
TE gives the stranding specs and they’re exactly what they’re supposed to be, but because this wire can be ordered with a large array of conductor materials (even aluminum!), you can’t make any sweeping statements about the resistivity of the entire series. You’d need to look at exactly which part you are using.
Also, one reason for not finding specs in the datasheet/catalog is because like many mil-spec parts, they simply leave it up to the relevant military specification to actually spell out the specs. In the case of SPEC44, this is AS81044.
If you look at AS81044 itself (
https://quicksearch.dla.mil/qsDocDetails.aspx?ident_number=32010 ) you’ll find a table on page 7 of the stranding and resistance specs. They vary significantly by material.
As for stranded vs. solid:
“Cross-section” of wire means the copper area, you do not include the air. So saying “stranded is 20% more in cross section” is dead wrong by definition. I know what you mean, but I think it’s important to mention this. 18AWG stranded has the same cross-section as 18AWG solid. Most, but not all, wire strippers state their sizes for solid wire. (I’d love to see this changed, since we use mostly stranded wire nowadays, other than in-wall mains wires.) With a stripper labeled for solid, you should
never be able to strip stranded wire in the nest of the stated AWG, never mind in one with a thinner gauge (higher gauge number).
So when you say that you’ve always had to strip 16AWG with 18AWG strippers, that’s categorically impossible, except in the unlikely scenario that you were stripping 16AWG
solid wire with a stripper labeled for 16AWG
stranded wire, because 16AWG stranded has a larger overall conductor diameter than 16AWG solid, and that in turn is larger than 18AWG stranded, and that larger than 18AWG solid. (16AWG solid has a practically identical diameter to the overall conductor diameter of 18AWG 19x30 stranded.)
Have you accounted for the stranding? Raychem 44 is stranded, and so the diameter from TE might be specified as the effective AWG diameter for terminating into connectors and such. Stranding will make the wire more resistive. In fact probably 25-30% more resistive is about right.
TE isn’t listing a conductor diameter at all. AWG is always a cross-section, so the resistivity is the same regardless of the stranding. (The ampacity, however, may vary, since the air gaps can affect heat dissipation.)
Wikipedia sums it up nicely: “AWG can also used to describe stranded wire. The AWG of a stranded wire represents the sum of the cross-sectional diameter of the individual strands; the gaps between strands are not counted. When made with circular strands, these gaps occupy about 25% of the wire area, thus requiring the overall bundle diameter to be about 13% larger than a solid wire of equal gauge.”
TE lists the conductor stranding specs, and they’re exactly what they should be, identical to two other brands I compared (Alpha and Belden).
*One can, of course, also provide an overall conductor diameter as well, which will vary depending on the stranding and any platings applied, since they do not count towards the cross-section.